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* [PATCH v4 00/22] btrfs: async discard support
@ 2019-11-25 19:46 Dennis Zhou
  2019-11-25 19:46 ` [PATCH 01/22] bitmap: genericize percpu bitmap region iterators Dennis Zhou
                   ` (22 more replies)
  0 siblings, 23 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Hello,

v3 [1] had 2 minor issues which are fixed:
 - I was generically dividing u64 which made 32 bit arches unhappy. [2]
 - Uninitialized use of trim_state local variable [3]

I've gone through and fixed the apparent u64 divisions which passes the
make.cross build provided on the end of the series.

This is based on btrfs-devel#misc-next e88411ecf657.

[1] https://lore.kernel.org/linux-btrfs/cover.1574282259.git.dennis@kernel.org/
[2] https://lore.kernel.org/linux-btrfs/201911230623.j5g9qeNZ%25lkp@intel.com/
[3] https://lore.kernel.org/linux-btrfs/CAKwvOdn5j37AYzmoOsaSqyYdBkjqevbTrSyGQypB+G_NgxX0fQ@mail.gmail.com/

diffstats below:

Dennis Zhou (22):
  bitmap: genericize percpu bitmap region iterators
  btrfs: rename DISCARD opt to DISCARD_SYNC
  btrfs: keep track of which extents have been discarded
  btrfs: keep track of cleanliness of the bitmap
  btrfs: add the beginning of async discard, discard workqueue
  btrfs: handle empty block_group removal
  btrfs: discard one region at a time in async discard
  btrfs: add removal calls for sysfs debug/
  btrfs: make UUID/debug have its own kobject
  btrfs: add discard sysfs directory
  btrfs: track discardable extents for async discard
  btrfs: keep track of discardable_bytes
  btrfs: calculate discard delay based on number of extents
  btrfs: add bps discard rate limit
  btrfs: limit max discard size for async discard
  btrfs: make max async discard size tunable
  btrfs: have multiple discard lists
  btrfs: only keep track of data extents for async discard
  btrfs: keep track of discard reuse stats
  btrfs: add async discard header
  btrfs: increase the metadata allowance for the free_space_cache
  btrfs: make smaller extents more likely to go into bitmaps

 fs/btrfs/Makefile           |   2 +-
 fs/btrfs/block-group.c      |  56 ++-
 fs/btrfs/block-group.h      |  30 ++
 fs/btrfs/ctree.h            |  52 ++-
 fs/btrfs/discard.c          | 680 ++++++++++++++++++++++++++++++++++++
 fs/btrfs/discard.h          |  46 +++
 fs/btrfs/disk-io.c          |  15 +-
 fs/btrfs/extent-tree.c      |  23 +-
 fs/btrfs/free-space-cache.c | 587 ++++++++++++++++++++++++++-----
 fs/btrfs/free-space-cache.h |  39 ++-
 fs/btrfs/inode-map.c        |  13 +-
 fs/btrfs/scrub.c            |   7 +-
 fs/btrfs/super.c            |  39 ++-
 fs/btrfs/sysfs.c            | 205 ++++++++++-
 include/linux/bitmap.h      |  35 ++
 mm/percpu.c                 |  61 +---
 16 files changed, 1737 insertions(+), 153 deletions(-)
 create mode 100644 fs/btrfs/discard.c
 create mode 100644 fs/btrfs/discard.h

Thanks,
Dennis

^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 01/22] bitmap: genericize percpu bitmap region iterators
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 02/22] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
                   ` (21 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Bitmaps are fairly popular for their space efficiency, but we don't have
generic iterators available. Make percpu's bitmap region iterators
available to everyone.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 include/linux/bitmap.h | 35 ++++++++++++++++++++++++
 mm/percpu.c            | 61 +++++++++++-------------------------------
 2 files changed, 51 insertions(+), 45 deletions(-)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 29fc933df3bf..9c31b5268f7a 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -438,6 +438,41 @@ static inline int bitmap_parse(const char *buf, unsigned int buflen,
 	return __bitmap_parse(buf, buflen, 0, maskp, nmaskbits);
 }
 
+static inline void bitmap_next_clear_region(unsigned long *bitmap,
+					    unsigned int *rs, unsigned int *re,
+					    unsigned int end)
+{
+	*rs = find_next_zero_bit(bitmap, end, *rs);
+	*re = find_next_bit(bitmap, end, *rs + 1);
+}
+
+static inline void bitmap_next_set_region(unsigned long *bitmap,
+					  unsigned int *rs, unsigned int *re,
+					  unsigned int end)
+{
+	*rs = find_next_bit(bitmap, end, *rs);
+	*re = find_next_zero_bit(bitmap, end, *rs + 1);
+}
+
+/*
+ * Bitmap region iterators.  Iterates over the bitmap between [@start, @end).
+ * @rs and @re should be integer variables and will be set to start and end
+ * index of the current clear or set region.
+ */
+#define bitmap_for_each_clear_region(bitmap, rs, re, start, end)	     \
+	for ((rs) = (start),						     \
+	     bitmap_next_clear_region((bitmap), &(rs), &(re), (end));	     \
+	     (rs) < (re);						     \
+	     (rs) = (re) + 1,						     \
+	     bitmap_next_clear_region((bitmap), &(rs), &(re), (end)))
+
+#define bitmap_for_each_set_region(bitmap, rs, re, start, end)		     \
+	for ((rs) = (start),						     \
+	     bitmap_next_set_region((bitmap), &(rs), &(re), (end));	     \
+	     (rs) < (re);						     \
+	     (rs) = (re) + 1,						     \
+	     bitmap_next_set_region((bitmap), &(rs), &(re), (end)))
+
 /**
  * BITMAP_FROM_U64() - Represent u64 value in the format suitable for bitmap.
  * @n: u64 value
diff --git a/mm/percpu.c b/mm/percpu.c
index 7e06a1e58720..e9844086b236 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -270,33 +270,6 @@ static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
 	       pcpu_unit_page_offset(cpu, page_idx);
 }
 
-static void pcpu_next_unpop(unsigned long *bitmap, int *rs, int *re, int end)
-{
-	*rs = find_next_zero_bit(bitmap, end, *rs);
-	*re = find_next_bit(bitmap, end, *rs + 1);
-}
-
-static void pcpu_next_pop(unsigned long *bitmap, int *rs, int *re, int end)
-{
-	*rs = find_next_bit(bitmap, end, *rs);
-	*re = find_next_zero_bit(bitmap, end, *rs + 1);
-}
-
-/*
- * Bitmap region iterators.  Iterates over the bitmap between
- * [@start, @end) in @chunk.  @rs and @re should be integer variables
- * and will be set to start and end index of the current free region.
- */
-#define pcpu_for_each_unpop_region(bitmap, rs, re, start, end)		     \
-	for ((rs) = (start), pcpu_next_unpop((bitmap), &(rs), &(re), (end)); \
-	     (rs) < (re);						     \
-	     (rs) = (re) + 1, pcpu_next_unpop((bitmap), &(rs), &(re), (end)))
-
-#define pcpu_for_each_pop_region(bitmap, rs, re, start, end)		     \
-	for ((rs) = (start), pcpu_next_pop((bitmap), &(rs), &(re), (end));   \
-	     (rs) < (re);						     \
-	     (rs) = (re) + 1, pcpu_next_pop((bitmap), &(rs), &(re), (end)))
-
 /*
  * The following are helper functions to help access bitmaps and convert
  * between bitmap offsets to address offsets.
@@ -732,9 +705,8 @@ static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk, bool full_scan)
 	}
 
 	bits = 0;
-	pcpu_for_each_md_free_region(chunk, bit_off, bits) {
+	pcpu_for_each_md_free_region(chunk, bit_off, bits)
 		pcpu_block_update(chunk_md, bit_off, bit_off + bits);
-	}
 }
 
 /**
@@ -749,7 +721,7 @@ static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index)
 {
 	struct pcpu_block_md *block = chunk->md_blocks + index;
 	unsigned long *alloc_map = pcpu_index_alloc_map(chunk, index);
-	int rs, re, start;	/* region start, region end */
+	unsigned int rs, re, start;	/* region start, region end */
 
 	/* promote scan_hint to contig_hint */
 	if (block->scan_hint) {
@@ -765,10 +737,9 @@ static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index)
 	block->right_free = 0;
 
 	/* iterate over free areas and update the contig hints */
-	pcpu_for_each_unpop_region(alloc_map, rs, re, start,
-				   PCPU_BITMAP_BLOCK_BITS) {
+	bitmap_for_each_clear_region(alloc_map, rs, re, start,
+				     PCPU_BITMAP_BLOCK_BITS)
 		pcpu_block_update(block, rs, re);
-	}
 }
 
 /**
@@ -1041,13 +1012,13 @@ static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
 static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
 			      int *next_off)
 {
-	int page_start, page_end, rs, re;
+	unsigned int page_start, page_end, rs, re;
 
 	page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
 	page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
 
 	rs = page_start;
-	pcpu_next_unpop(chunk->populated, &rs, &re, page_end);
+	bitmap_next_clear_region(chunk->populated, &rs, &re, page_end);
 	if (rs >= page_end)
 		return true;
 
@@ -1702,13 +1673,13 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 
 	/* populate if not all pages are already there */
 	if (!is_atomic) {
-		int page_start, page_end, rs, re;
+		unsigned int page_start, page_end, rs, re;
 
 		page_start = PFN_DOWN(off);
 		page_end = PFN_UP(off + size);
 
-		pcpu_for_each_unpop_region(chunk->populated, rs, re,
-					   page_start, page_end) {
+		bitmap_for_each_clear_region(chunk->populated, rs, re,
+					     page_start, page_end) {
 			WARN_ON(chunk->immutable);
 
 			ret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);
@@ -1858,10 +1829,10 @@ static void pcpu_balance_workfn(struct work_struct *work)
 	spin_unlock_irq(&pcpu_lock);
 
 	list_for_each_entry_safe(chunk, next, &to_free, list) {
-		int rs, re;
+		unsigned int rs, re;
 
-		pcpu_for_each_pop_region(chunk->populated, rs, re, 0,
-					 chunk->nr_pages) {
+		bitmap_for_each_set_region(chunk->populated, rs, re, 0,
+					   chunk->nr_pages) {
 			pcpu_depopulate_chunk(chunk, rs, re);
 			spin_lock_irq(&pcpu_lock);
 			pcpu_chunk_depopulated(chunk, rs, re);
@@ -1893,7 +1864,7 @@ static void pcpu_balance_workfn(struct work_struct *work)
 	}
 
 	for (slot = pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot++) {
-		int nr_unpop = 0, rs, re;
+		unsigned int nr_unpop = 0, rs, re;
 
 		if (!nr_to_pop)
 			break;
@@ -1910,9 +1881,9 @@ static void pcpu_balance_workfn(struct work_struct *work)
 			continue;
 
 		/* @chunk can't go away while pcpu_alloc_mutex is held */
-		pcpu_for_each_unpop_region(chunk->populated, rs, re, 0,
-					   chunk->nr_pages) {
-			int nr = min(re - rs, nr_to_pop);
+		bitmap_for_each_clear_region(chunk->populated, rs, re, 0,
+					     chunk->nr_pages) {
+			int nr = min_t(int, re - rs, nr_to_pop);
 
 			ret = pcpu_populate_chunk(chunk, rs, rs + nr, gfp);
 			if (!ret) {
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 02/22] btrfs: rename DISCARD opt to DISCARD_SYNC
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
  2019-11-25 19:46 ` [PATCH 01/22] bitmap: genericize percpu bitmap region iterators Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 03/22] btrfs: keep track of which extents have been discarded Dennis Zhou
                   ` (20 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

This series introduces async discard which will use the flag
DISCARD_ASYNC, so rename the original flag to DISCARD_SYNC as it is
synchronously done in transaction commit.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 fs/btrfs/block-group.c | 2 +-
 fs/btrfs/ctree.h       | 2 +-
 fs/btrfs/extent-tree.c | 4 ++--
 fs/btrfs/super.c       | 8 ++++----
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 6934a5b8708f..6064be2d5556 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1363,7 +1363,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		spin_unlock(&space_info->lock);
 
 		/* DISCARD can flip during remount */
-		trimming = btrfs_test_opt(fs_info, DISCARD);
+		trimming = btrfs_test_opt(fs_info, DISCARD_SYNC);
 
 		/* Implicit trim during transaction commit. */
 		if (trimming)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b2e8fd8a8e59..8ac3b2deef4a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1170,7 +1170,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
 #define BTRFS_MOUNT_FLUSHONCOMMIT       (1 << 7)
 #define BTRFS_MOUNT_SSD_SPREAD		(1 << 8)
 #define BTRFS_MOUNT_NOSSD		(1 << 9)
-#define BTRFS_MOUNT_DISCARD		(1 << 10)
+#define BTRFS_MOUNT_DISCARD_SYNC	(1 << 10)
 #define BTRFS_MOUNT_FORCE_COMPRESS      (1 << 11)
 #define BTRFS_MOUNT_SPACE_CACHE		(1 << 12)
 #define BTRFS_MOUNT_CLEAR_CACHE		(1 << 13)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 18df434bfe52..f979f4c1a385 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2923,7 +2923,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 			break;
 		}
 
-		if (btrfs_test_opt(fs_info, DISCARD))
+		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
 			ret = btrfs_discard_extent(fs_info, start,
 						   end + 1 - start, NULL);
 
@@ -4181,7 +4181,7 @@ static int __btrfs_free_reserved_extent(struct btrfs_fs_info *fs_info,
 	if (pin)
 		pin_down_extent(cache, start, len, 1);
 	else {
-		if (btrfs_test_opt(fs_info, DISCARD))
+		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
 			ret = btrfs_discard_extent(fs_info, start, len, NULL);
 		btrfs_add_free_space(cache, start, len);
 		btrfs_free_reserved_bytes(cache, len, delalloc);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a98c3c71fc54..f131fb9f0f69 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -695,11 +695,11 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 				   info->metadata_ratio);
 			break;
 		case Opt_discard:
-			btrfs_set_and_info(info, DISCARD,
-					   "turning on discard");
+			btrfs_set_and_info(info, DISCARD_SYNC,
+					   "turning on sync discard");
 			break;
 		case Opt_nodiscard:
-			btrfs_clear_and_info(info, DISCARD,
+			btrfs_clear_and_info(info, DISCARD_SYNC,
 					     "turning off discard");
 			break;
 		case Opt_space_cache:
@@ -1322,7 +1322,7 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",nologreplay");
 	if (btrfs_test_opt(info, FLUSHONCOMMIT))
 		seq_puts(seq, ",flushoncommit");
-	if (btrfs_test_opt(info, DISCARD))
+	if (btrfs_test_opt(info, DISCARD_SYNC))
 		seq_puts(seq, ",discard");
 	if (!(info->sb->s_flags & SB_POSIXACL))
 		seq_puts(seq, ",noacl");
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 03/22] btrfs: keep track of which extents have been discarded
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
  2019-11-25 19:46 ` [PATCH 01/22] bitmap: genericize percpu bitmap region iterators Dennis Zhou
  2019-11-25 19:46 ` [PATCH 02/22] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
                   ` (19 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Async discard will use the free space cache as backing knowledge for
which extents to discard. This patch plumbs knowledge about which
extents need to be discarded into the free space cache from
unpin_extent_range().

An untrimmed extent can merge with everything as this is a new region.
Absorbing trimmed extents is a tradeoff to for greater coalescing which
makes life better for find_free_extent(). Additionally, it seems the
size of a trim isn't as problematic as the trim io itself.

When reading in the free space cache from disk, if sync is set, mark all
extents as trimmed. The current code ensures at transaction commit that
all free space is trimmed when sync is set, so this reflects that.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/extent-tree.c      | 15 +++++++---
 fs/btrfs/free-space-cache.c | 59 ++++++++++++++++++++++++++++++++-----
 fs/btrfs/free-space-cache.h | 17 ++++++++++-
 fs/btrfs/inode-map.c        | 13 ++++----
 4 files changed, 86 insertions(+), 18 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f979f4c1a385..5dc696d0c5b2 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2803,6 +2803,7 @@ fetch_cluster_info(struct btrfs_fs_info *fs_info,
 
 static int unpin_extent_range(struct btrfs_fs_info *fs_info,
 			      u64 start, u64 end,
+			      enum btrfs_trim_state trim_state,
 			      const bool return_free_space)
 {
 	struct btrfs_block_group *cache = NULL;
@@ -2836,7 +2837,9 @@ static int unpin_extent_range(struct btrfs_fs_info *fs_info,
 		if (start < cache->last_byte_to_unpin) {
 			len = min(len, cache->last_byte_to_unpin - start);
 			if (return_free_space)
-				btrfs_add_free_space(cache, start, len);
+				__btrfs_add_free_space(fs_info,
+						       cache->free_space_ctl,
+						       start, len, trim_state);
 		}
 
 		start += len;
@@ -2914,6 +2917,7 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 
 	while (!trans->aborted) {
 		struct extent_state *cached_state = NULL;
+		enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 
 		mutex_lock(&fs_info->unused_bg_unpin_mutex);
 		ret = find_first_extent_bit(unpin, 0, &start, &end,
@@ -2923,12 +2927,14 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 			break;
 		}
 
-		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
+		if (btrfs_test_opt(fs_info, DISCARD_SYNC)) {
 			ret = btrfs_discard_extent(fs_info, start,
 						   end + 1 - start, NULL);
+			trim_state = BTRFS_TRIM_STATE_TRIMMED;
+		}
 
 		clear_extent_dirty(unpin, start, end, &cached_state);
-		unpin_extent_range(fs_info, start, end, true);
+		unpin_extent_range(fs_info, start, end, trim_state, true);
 		mutex_unlock(&fs_info->unused_bg_unpin_mutex);
 		free_extent_state(cached_state);
 		cond_resched();
@@ -5546,7 +5552,8 @@ u64 btrfs_account_ro_block_groups_free_space(struct btrfs_space_info *sinfo)
 int btrfs_error_unpin_extent_range(struct btrfs_fs_info *fs_info,
 				   u64 start, u64 end)
 {
-	return unpin_extent_range(fs_info, start, end, false);
+	return unpin_extent_range(fs_info, start, end,
+				  BTRFS_TRIM_STATE_UNTRIMMED, false);
 }
 
 /*
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 3283da419200..399c641440bc 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -752,6 +752,14 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 			goto free_cache;
 		}
 
+		/*
+		 * Sync discard ensures that the free space cache is always
+		 * trimmed.  So when reading this in, the state should reflect
+		 * that.
+		 */
+		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
+			e->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+
 		if (!e->bytes) {
 			kmem_cache_free(btrfs_free_space_cachep, e);
 			goto free_cache;
@@ -2161,6 +2169,22 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
 	return ret;
 }
 
+/*
+ * Free space merging rules:
+ *  1) Merge trimmed areas together
+ *  2) Let untrimmed areas coalesce with trimmed areas
+ *  3) Always pull neighboring regions from bitmaps
+ *
+ * The above rules are for when we merge free space based on btrfs_trim_state.
+ * Rules 2 and 3 are subtle because they are suboptimal, but are done for the
+ * same reason: to promote larger extent regions which makes life easier for
+ * find_free_extent().  Rule 2 enables coalescing based on the common path
+ * being returning free space from btrfs_finish_extent_commit().  So when free
+ * space is trimmed, it will prevent aggregating trimmed new region and
+ * untrimmed regions in the rb_tree.  Rule 3 is purely to obtain larger extents
+ * and provide find_free_extent() with the largest extents possible hoping for
+ * the reuse path.
+ */
 static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 			  struct btrfs_free_space *info, bool update_stat)
 {
@@ -2169,6 +2193,7 @@ static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 	bool merged = false;
 	u64 offset = info->offset;
 	u64 bytes = info->bytes;
+	const bool is_trimmed = btrfs_free_space_trimmed(info);
 
 	/*
 	 * first we want to see if there is free space adjacent to the range we
@@ -2182,7 +2207,9 @@ static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 	else
 		left_info = tree_search_offset(ctl, offset - 1, 0, 0);
 
-	if (right_info && !right_info->bitmap) {
+	/* See try_merge_free_space() comment. */
+	if (right_info && !right_info->bitmap &&
+	    (!is_trimmed || btrfs_free_space_trimmed(right_info))) {
 		if (update_stat)
 			unlink_free_space(ctl, right_info);
 		else
@@ -2192,8 +2219,10 @@ static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
 		merged = true;
 	}
 
+	/* See try_merge_free_space() comment. */
 	if (left_info && !left_info->bitmap &&
-	    left_info->offset + left_info->bytes == offset) {
+	    left_info->offset + left_info->bytes == offset &&
+	    (!is_trimmed || btrfs_free_space_trimmed(left_info))) {
 		if (update_stat)
 			unlink_free_space(ctl, left_info);
 		else
@@ -2229,6 +2258,10 @@ static bool steal_from_bitmap_to_end(struct btrfs_free_space_ctl *ctl,
 	bytes = (j - i) * ctl->unit;
 	info->bytes += bytes;
 
+	/* See try_merge_free_space() comment. */
+	if (!btrfs_free_space_trimmed(bitmap))
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
 	if (update_stat)
 		bitmap_clear_bits(ctl, bitmap, end, bytes);
 	else
@@ -2282,6 +2315,10 @@ static bool steal_from_bitmap_to_front(struct btrfs_free_space_ctl *ctl,
 	info->offset -= bytes;
 	info->bytes += bytes;
 
+	/* See try_merge_free_space() comment. */
+	if (!btrfs_free_space_trimmed(bitmap))
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
 	if (update_stat)
 		bitmap_clear_bits(ctl, bitmap, info->offset, bytes);
 	else
@@ -2331,7 +2368,8 @@ static void steal_from_bitmap(struct btrfs_free_space_ctl *ctl,
 
 int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 			   struct btrfs_free_space_ctl *ctl,
-			   u64 offset, u64 bytes)
+			   u64 offset, u64 bytes,
+			   enum btrfs_trim_state trim_state)
 {
 	struct btrfs_free_space *info;
 	int ret = 0;
@@ -2342,6 +2380,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 
 	info->offset = offset;
 	info->bytes = bytes;
+	info->trim_state = trim_state;
 	RB_CLEAR_NODE(&info->offset_index);
 
 	spin_lock(&ctl->tree_lock);
@@ -2389,7 +2428,7 @@ int btrfs_add_free_space(struct btrfs_block_group *block_group,
 {
 	return __btrfs_add_free_space(block_group->fs_info,
 				      block_group->free_space_ctl,
-				      bytenr, size);
+				      bytenr, size, 0);
 }
 
 int btrfs_remove_free_space(struct btrfs_block_group *block_group,
@@ -2464,8 +2503,11 @@ int btrfs_remove_free_space(struct btrfs_block_group *block_group,
 			}
 			spin_unlock(&ctl->tree_lock);
 
-			ret = btrfs_add_free_space(block_group, offset + bytes,
-						   old_end - (offset + bytes));
+			ret = __btrfs_add_free_space(block_group->fs_info,
+						     ctl,
+						     offset + bytes,
+						     old_end - (offset + bytes),
+						     info->trim_state);
 			WARN_ON(ret);
 			goto out;
 		}
@@ -2634,6 +2676,7 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 	u64 ret = 0;
 	u64 align_gap = 0;
 	u64 align_gap_len = 0;
+	enum btrfs_trim_state align_gap_trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 
 	spin_lock(&ctl->tree_lock);
 	entry = find_free_space(ctl, &offset, &bytes_search,
@@ -2650,6 +2693,7 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 		unlink_free_space(ctl, entry);
 		align_gap_len = offset - entry->offset;
 		align_gap = entry->offset;
+		align_gap_trim_state = entry->trim_state;
 
 		entry->offset = offset + bytes;
 		WARN_ON(entry->bytes < bytes + align_gap_len);
@@ -2665,7 +2709,8 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 
 	if (align_gap_len)
 		__btrfs_add_free_space(block_group->fs_info, ctl,
-				       align_gap, align_gap_len);
+				       align_gap, align_gap_len,
+				       align_gap_trim_state);
 	return ret;
 }
 
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index ba9a23241101..66c073f854dc 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -6,6 +6,14 @@
 #ifndef BTRFS_FREE_SPACE_CACHE_H
 #define BTRFS_FREE_SPACE_CACHE_H
 
+/*
+ * This is the trim state of an extent or bitmap.
+ */
+enum btrfs_trim_state {
+	BTRFS_TRIM_STATE_UNTRIMMED,
+	BTRFS_TRIM_STATE_TRIMMED,
+};
+
 struct btrfs_free_space {
 	struct rb_node offset_index;
 	u64 offset;
@@ -13,8 +21,14 @@ struct btrfs_free_space {
 	u64 max_extent_size;
 	unsigned long *bitmap;
 	struct list_head list;
+	enum btrfs_trim_state trim_state;
 };
 
+static inline bool btrfs_free_space_trimmed(struct btrfs_free_space *info)
+{
+	return (info->trim_state == BTRFS_TRIM_STATE_TRIMMED);
+}
+
 struct btrfs_free_space_ctl {
 	spinlock_t tree_lock;
 	struct rb_root free_space_offset;
@@ -83,7 +97,8 @@ int btrfs_write_out_ino_cache(struct btrfs_root *root,
 void btrfs_init_free_space_ctl(struct btrfs_block_group *block_group);
 int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 			   struct btrfs_free_space_ctl *ctl,
-			   u64 bytenr, u64 size);
+			   u64 bytenr, u64 size,
+			   enum btrfs_trim_state trim_state);
 int btrfs_add_free_space(struct btrfs_block_group *block_group,
 			 u64 bytenr, u64 size);
 int btrfs_remove_free_space(struct btrfs_block_group *block_group,
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 37345fb6191d..d5c9c69d8263 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -107,7 +107,7 @@ static int caching_kthread(void *data)
 
 		if (last != (u64)-1 && last + 1 != key.objectid) {
 			__btrfs_add_free_space(fs_info, ctl, last + 1,
-					       key.objectid - last - 1);
+					       key.objectid - last - 1, 0);
 			wake_up(&root->ino_cache_wait);
 		}
 
@@ -118,7 +118,7 @@ static int caching_kthread(void *data)
 
 	if (last < root->highest_objectid - 1) {
 		__btrfs_add_free_space(fs_info, ctl, last + 1,
-				       root->highest_objectid - last - 1);
+				       root->highest_objectid - last - 1, 0);
 	}
 
 	spin_lock(&root->ino_cache_lock);
@@ -175,7 +175,8 @@ static void start_caching(struct btrfs_root *root)
 	ret = btrfs_find_free_objectid(root, &objectid);
 	if (!ret && objectid <= BTRFS_LAST_FREE_OBJECTID) {
 		__btrfs_add_free_space(fs_info, ctl, objectid,
-				       BTRFS_LAST_FREE_OBJECTID - objectid + 1);
+				       BTRFS_LAST_FREE_OBJECTID - objectid + 1,
+				       0);
 		wake_up(&root->ino_cache_wait);
 	}
 
@@ -221,7 +222,7 @@ void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
 		return;
 again:
 	if (root->ino_cache_state == BTRFS_CACHE_FINISHED) {
-		__btrfs_add_free_space(fs_info, pinned, objectid, 1);
+		__btrfs_add_free_space(fs_info, pinned, objectid, 1, 0);
 	} else {
 		down_write(&fs_info->commit_root_sem);
 		spin_lock(&root->ino_cache_lock);
@@ -234,7 +235,7 @@ void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
 
 		start_caching(root);
 
-		__btrfs_add_free_space(fs_info, pinned, objectid, 1);
+		__btrfs_add_free_space(fs_info, pinned, objectid, 1, 0);
 
 		up_write(&fs_info->commit_root_sem);
 	}
@@ -281,7 +282,7 @@ void btrfs_unpin_free_ino(struct btrfs_root *root)
 		spin_unlock(rbroot_lock);
 		if (count)
 			__btrfs_add_free_space(root->fs_info, ctl,
-					       info->offset, count);
+					       info->offset, count, 0);
 		kmem_cache_free(btrfs_free_space_cachep, info);
 	}
 }
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (2 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 03/22] btrfs: keep track of which extents have been discarded Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 05/22] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
                   ` (18 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

There is a cap in btrfs in the amount of free extents that a block group
can have. When it surpasses that threshold, future extents are placed
into bitmaps. Instead of keeping track of if a certain bit is trimmed or
not in a second bitmap, keep track of the relative state of the bitmap.

With async discard, trimming bitmaps becomes a more frequent operation.
As a trade off with simplicity, we keep track of if discarding a bitmap
is in progress. If we fully scan a bitmap and trim as necessary, the
bitmap is marked clean. This has some caveats as the min block size may
skip over regions deemed too small. But this should be a reasonable
trade off rather than keeping a second bitmap and making allocation
paths more complex. The downside is we may overtrim, but ideally the min
block size should prevent us from doing that too often and getting stuck
trimming pathological cases.

BTRFS_TRIM_STATE_TRIMMING is added to indicate a bitmap is in the
process of being trimmed. If additional free space is added to that
bitmap, the bit is cleared. A bitmap will be marked
BTRFS_TRIM_STATE_TRIMMED if the trimming code was able to reach the end
of it and the former is still set.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/free-space-cache.c | 91 +++++++++++++++++++++++++++++++++----
 fs/btrfs/free-space-cache.h | 12 +++++
 2 files changed, 94 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 399c641440bc..49ae1e6ee104 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1979,11 +1979,18 @@ static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
 
 static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
 			       struct btrfs_free_space *info, u64 offset,
-			       u64 bytes)
+			       u64 bytes, enum btrfs_trim_state trim_state)
 {
 	u64 bytes_to_set = 0;
 	u64 end;
 
+	/*
+	 * This is a tradeoff to make bitmap trim state minimal.  We mark the
+	 * whole bitmap untrimmed if at any point we add untrimmed regions.
+	 */
+	if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED)
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
 	end = info->offset + (u64)(BITS_PER_BITMAP * ctl->unit);
 
 	bytes_to_set = min(end - offset, bytes);
@@ -2058,10 +2065,12 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
 	struct btrfs_block_group *block_group = NULL;
 	int added = 0;
 	u64 bytes, offset, bytes_added;
+	enum btrfs_trim_state trim_state;
 	int ret;
 
 	bytes = info->bytes;
 	offset = info->offset;
+	trim_state = info->trim_state;
 
 	if (!ctl->op->use_bitmap(ctl, info))
 		return 0;
@@ -2096,8 +2105,8 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
 		}
 
 		if (entry->offset == offset_to_bitmap(ctl, offset)) {
-			bytes_added = add_bytes_to_bitmap(ctl, entry,
-							  offset, bytes);
+			bytes_added = add_bytes_to_bitmap(ctl, entry, offset,
+							  bytes, trim_state);
 			bytes -= bytes_added;
 			offset += bytes_added;
 		}
@@ -2116,7 +2125,8 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
 		goto new_bitmap;
 	}
 
-	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+					  trim_state);
 	bytes -= bytes_added;
 	offset += bytes_added;
 	added = 0;
@@ -2150,6 +2160,7 @@ static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
 		/* allocate the bitmap */
 		info->bitmap = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep,
 						 GFP_NOFS);
+		info->trim_state = BTRFS_TRIM_STATE_TRIMMED;
 		spin_lock(&ctl->tree_lock);
 		if (!info->bitmap) {
 			ret = -ENOMEM;
@@ -3320,6 +3331,39 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 	return ret;
 }
 
+/*
+ * If we break out of trimming a bitmap prematurely, we should reset the
+ * trimming bit.  In a rather contrieved case, it's possible to race here so
+ * reset the state to BTRFS_TRIM_STATE_UNTRIMMED.
+ *
+ * start = start of bitmap
+ * end = near end of bitmap
+ *
+ * Thread 1:			Thread 2:
+ * trim_bitmaps(start)
+ *				trim_bitmaps(end)
+ *				end_trimming_bitmap()
+ * reset_trimming_bitmap()
+ */
+static void reset_trimming_bitmap(struct btrfs_free_space_ctl *ctl, u64 offset)
+{
+	struct btrfs_free_space *entry;
+
+	spin_lock(&ctl->tree_lock);
+
+	entry = tree_search_offset(ctl, offset, 1, 0);
+	if (entry)
+		entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+	spin_unlock(&ctl->tree_lock);
+}
+
+static void end_trimming_bitmap(struct btrfs_free_space *entry)
+{
+	if (btrfs_free_space_trimming_bitmap(entry))
+		entry->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+}
+
 static int trim_bitmaps(struct btrfs_block_group *block_group,
 			u64 *total_trimmed, u64 start, u64 end, u64 minlen)
 {
@@ -3344,16 +3388,33 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		}
 
 		entry = tree_search_offset(ctl, offset, 1, 0);
-		if (!entry) {
+		if (!entry || btrfs_free_space_trimmed(entry)) {
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			next_bitmap = true;
 			goto next;
 		}
 
+		/*
+		 * Async discard bitmap trimming begins at by setting the start
+		 * to be key.objectid and the offset_to_bitmap() aligns to the
+		 * start of the bitmap.  This lets us know we are fully
+		 * scanning the bitmap rather than only some portion of it.
+		 */
+		if (start == offset)
+			entry->trim_state = BTRFS_TRIM_STATE_TRIMMING;
+
 		bytes = minlen;
 		ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
 		if (ret2 || start >= end) {
+			/*
+			 * This keeps the invariant that all bytes are trimmed
+			 * if BTRFS_TRIM_STATE_TRIMMED is set on a bitmap.
+			 */
+			if (ret2 && !minlen)
+				end_trimming_bitmap(entry);
+			else
+				entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			next_bitmap = true;
@@ -3362,6 +3423,7 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 
 		bytes = min(bytes, end - start);
 		if (bytes < minlen) {
+			entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			goto next;
@@ -3379,18 +3441,21 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
 				  start, bytes, &trim_entry);
-		if (ret)
+		if (ret) {
+			reset_trimming_bitmap(ctl, offset);
 			break;
+		}
 next:
 		if (next_bitmap) {
 			offset += BITS_PER_BITMAP * ctl->unit;
+			start = offset;
 		} else {
 			start += bytes;
-			if (start >= offset + BITS_PER_BITMAP * ctl->unit)
-				offset += BITS_PER_BITMAP * ctl->unit;
 		}
 
 		if (fatal_signal_pending(current)) {
+			if (start != offset)
+				reset_trimming_bitmap(ctl, offset);
 			ret = -ERESTARTSYS;
 			break;
 		}
@@ -3444,7 +3509,9 @@ void btrfs_put_block_group_trimming(struct btrfs_block_group *block_group)
 int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 			   u64 *trimmed, u64 start, u64 end, u64 minlen)
 {
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	int ret;
+	u64 rem = 0;
 
 	*trimmed = 0;
 
@@ -3461,6 +3528,10 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 		goto out;
 
 	ret = trim_bitmaps(block_group, trimmed, start, end, minlen);
+	div64_u64_rem(end, BITS_PER_BITMAP * ctl->unit, &rem);
+	/* If we ended in the middle of a bitmap, reset the trimming flag. */
+	if (rem)
+		reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end));
 out:
 	btrfs_put_block_group_trimming(block_group);
 	return ret;
@@ -3645,6 +3716,7 @@ int test_add_free_space_entry(struct btrfs_block_group *cache,
 	struct btrfs_free_space_ctl *ctl = cache->free_space_ctl;
 	struct btrfs_free_space *info = NULL, *bitmap_info;
 	void *map = NULL;
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_TRIMMED;
 	u64 bytes_added;
 	int ret;
 
@@ -3686,7 +3758,8 @@ int test_add_free_space_entry(struct btrfs_block_group *cache,
 		info = NULL;
 	}
 
-	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+					  trim_state);
 
 	bytes -= bytes_added;
 	offset += bytes_added;
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 66c073f854dc..29d16f58b40b 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -8,10 +8,16 @@
 
 /*
  * This is the trim state of an extent or bitmap.
+ *
+ * BTRFS_TRIM_STATE_TRIMMING is special and used to maintain the state of a
+ * bitmap as we may need several trims to fully trim a single bitmap entry.
+ * This is reset should any free space other than trimmed space is added to the
+ * bitmap.
  */
 enum btrfs_trim_state {
 	BTRFS_TRIM_STATE_UNTRIMMED,
 	BTRFS_TRIM_STATE_TRIMMED,
+	BTRFS_TRIM_STATE_TRIMMING,
 };
 
 struct btrfs_free_space {
@@ -29,6 +35,12 @@ static inline bool btrfs_free_space_trimmed(struct btrfs_free_space *info)
 	return (info->trim_state == BTRFS_TRIM_STATE_TRIMMED);
 }
 
+static inline bool btrfs_free_space_trimming_bitmap(
+					    struct btrfs_free_space *info)
+{
+	return (info->trim_state == BTRFS_TRIM_STATE_TRIMMING);
+}
+
 struct btrfs_free_space_ctl {
 	spinlock_t tree_lock;
 	struct rb_root free_space_offset;
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 05/22] btrfs: add the beginning of async discard, discard workqueue
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (3 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 06/22] btrfs: handle empty block_group removal Dennis Zhou
                   ` (17 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

When discard is enabled, everytime a pinned extent is released back to
the block_group's free space cache, a discard is issued for the extent.
This is an overeager approach when it comes to discarding and helping
the SSD maintain enough free space to prevent severe garbage collection
situations.

This adds the beginning of async discard. Instead of issuing a discard
prior to returning it to the free space, it is just marked as untrimmed.
The block_group is then added to a LRU which then feeds into a workqueue
to issue discards at a much slower rate. Full discarding of unused block
groups is still done and will be address in a future patch in this
series.

For now, we don't persist the discard state of extents and bitmaps.
Therefore, our failure recovery mode will be to consider extents
untrimmed. This lets us handle failure and unmounting as one in the
same.

On a number of Facebook webservers, I collected data every minute
accounting the time we spent in btrfs_finish_extent_commit() (col. 1)
and in btrfs_commit_transaction() (col. 2). btrfs_finish_extent_commit()
is where we discard extents synchronously before returning them to the
free space cache.

discard=sync:
                 p99 total per minute       p99 total per minute
      Drive   |   extent_commit() (ms)  |    commit_trans() (ms)
    ---------------------------------------------------------------
     Drive A  |           434           |          1170
     Drive B  |           880           |          2330
     Drive C  |          2943           |          3920
     Drive D  |          4763           |          5701

discard=async:
                 p99 total per minute       p99 total per minute
      Drive   |   extent_commit() (ms)  |    commit_trans() (ms)
    --------------------------------------------------------------
     Drive A  |           134           |           956
     Drive B  |            64           |          1972
     Drive C  |            59           |          1032
     Drive D  |            62           |          1200

While it's not great that the stats are cumulative over 1m, all of these
servers are running the same workload and and the delta between the two
are substantial. We are spending significantly less time in
btrfs_finish_extent_commit() which is responsible for discarding.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/Makefile           |   2 +-
 fs/btrfs/block-group.c      |   4 +
 fs/btrfs/block-group.h      |   9 ++
 fs/btrfs/ctree.h            |  21 +++
 fs/btrfs/discard.c          | 273 ++++++++++++++++++++++++++++++++++++
 fs/btrfs/discard.h          |  26 ++++
 fs/btrfs/disk-io.c          |  15 +-
 fs/btrfs/extent-tree.c      |   4 +
 fs/btrfs/free-space-cache.c |  35 ++++-
 fs/btrfs/super.c            |  35 ++++-
 10 files changed, 414 insertions(+), 10 deletions(-)
 create mode 100644 fs/btrfs/discard.c
 create mode 100644 fs/btrfs/discard.h

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 82200dbca5ac..9a0ff3384381 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -11,7 +11,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
 	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
 	   uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o \
-	   block-rsv.o delalloc-space.o block-group.o
+	   block-rsv.o delalloc-space.o block-group.o discard.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 6064be2d5556..d2bc46c365f4 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -14,6 +14,7 @@
 #include "sysfs.h"
 #include "tree-log.h"
 #include "delalloc-space.h"
+#include "discard.h"
 
 /*
  * Return target flags in extended format or 0 if restripe for this chunk_type
@@ -1272,6 +1273,8 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		}
 		spin_unlock(&fs_info->unused_bgs_lock);
 
+		btrfs_discard_cancel_work(&fs_info->discard_ctl, block_group);
+
 		mutex_lock(&fs_info->delete_unused_bgs_mutex);
 
 		/* Don't want to race with allocators so take the groups_sem */
@@ -1617,6 +1620,7 @@ static struct btrfs_block_group *btrfs_create_block_group_cache(
 	INIT_LIST_HEAD(&cache->cluster_list);
 	INIT_LIST_HEAD(&cache->bg_list);
 	INIT_LIST_HEAD(&cache->ro_list);
+	INIT_LIST_HEAD(&cache->discard_list);
 	INIT_LIST_HEAD(&cache->dirty_list);
 	INIT_LIST_HEAD(&cache->io_list);
 	btrfs_init_free_space_ctl(cache);
diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index 9b409676c4b2..884defd61dcd 100644
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -116,7 +116,11 @@ struct btrfs_block_group {
 	/* For read-only block groups */
 	struct list_head ro_list;
 
+	/* For discard operations */
 	atomic_t trimming;
+	struct list_head discard_list;
+	int discard_index;
+	u64 discard_eligible_time;
 
 	/* For dirty block groups */
 	struct list_head dirty_list;
@@ -158,6 +162,11 @@ struct btrfs_block_group {
 	struct btrfs_full_stripe_locks_tree full_stripe_locks_root;
 };
 
+static inline u64 btrfs_block_group_end(struct btrfs_block_group *block_group)
+{
+	return (block_group->start + block_group->length);
+}
+
 #ifdef CONFIG_BTRFS_DEBUG
 static inline int btrfs_should_fragment_free_space(
 		struct btrfs_block_group *block_group)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8ac3b2deef4a..d5ce8054f074 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -440,6 +440,21 @@ struct btrfs_full_stripe_locks_tree {
 	struct mutex lock;
 };
 
+/* Discard control. */
+/*
+ * Async discard uses multiple lists to differentiate the discard filter
+ * parameters.
+ */
+#define BTRFS_NR_DISCARD_LISTS		1
+
+struct btrfs_discard_ctl {
+	struct workqueue_struct *discard_workers;
+	struct delayed_work work;
+	spinlock_t lock;
+	struct btrfs_block_group *block_group;
+	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
+};
+
 /* delayed seq elem */
 struct seq_list {
 	struct list_head list;
@@ -526,6 +541,9 @@ enum {
 	 * so we don't need to offload checksums to workqueues.
 	 */
 	BTRFS_FS_CSUM_IMPL_FAST,
+
+	/* Indicate that the discard workqueue can service discards. */
+	BTRFS_FS_DISCARD_RUNNING,
 };
 
 struct btrfs_fs_info {
@@ -816,6 +834,8 @@ struct btrfs_fs_info {
 	struct btrfs_workqueue *scrub_wr_completion_workers;
 	struct btrfs_workqueue *scrub_parity_workers;
 
+	struct btrfs_discard_ctl discard_ctl;
+
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 	u32 check_integrity_print_mask;
 #endif
@@ -1189,6 +1209,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
 #define BTRFS_MOUNT_FREE_SPACE_TREE	(1 << 26)
 #define BTRFS_MOUNT_NOLOGREPLAY		(1 << 27)
 #define BTRFS_MOUNT_REF_VERIFY		(1 << 28)
+#define BTRFS_MOUNT_DISCARD_ASYNC	(1 << 29)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(2048)
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
new file mode 100644
index 000000000000..15d54de3d682
--- /dev/null
+++ b/fs/btrfs/discard.c
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/ktime.h>
+#include <linux/list.h>
+#include <linux/sizes.h>
+#include <linux/workqueue.h>
+#include "ctree.h"
+#include "block-group.h"
+#include "discard.h"
+#include "free-space-cache.h"
+
+/* This is an initial delay to give some chance for lba reuse. */
+#define BTRFS_DISCARD_DELAY		(120ULL * NSEC_PER_SEC)
+
+static struct list_head *btrfs_get_discard_list(
+					struct btrfs_discard_ctl *discard_ctl,
+					struct btrfs_block_group *block_group)
+{
+	return &discard_ctl->discard_list[block_group->discard_index];
+}
+
+void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
+			       struct btrfs_block_group *block_group)
+{
+	spin_lock(&discard_ctl->lock);
+
+	if (list_empty(&block_group->discard_list))
+		block_group->discard_eligible_time = (ktime_get_ns() +
+						      BTRFS_DISCARD_DELAY);
+
+	list_move_tail(&block_group->discard_list,
+		       btrfs_get_discard_list(discard_ctl, block_group));
+
+	spin_unlock(&discard_ctl->lock);
+}
+
+static bool remove_from_discard_list(struct btrfs_discard_ctl *discard_ctl,
+				     struct btrfs_block_group *block_group)
+{
+	bool running = false;
+
+	spin_lock(&discard_ctl->lock);
+
+	if (block_group == discard_ctl->block_group) {
+		running = true;
+		discard_ctl->block_group = NULL;
+	}
+
+	block_group->discard_eligible_time = 0;
+	list_del_init(&block_group->discard_list);
+
+	spin_unlock(&discard_ctl->lock);
+
+	return running;
+}
+
+/**
+ * find_next_block_group - find block_group that's up next for discarding
+ * @discard_ctl: discard control
+ * @now: current time
+ *
+ * Iterate over the discard lists to find the next block_group up for
+ * discarding checking the discard_eligible_time of block_group.
+ */
+static struct btrfs_block_group *find_next_block_group(
+					struct btrfs_discard_ctl *discard_ctl,
+					u64 now)
+{
+	struct btrfs_block_group *ret_block_group = NULL, *block_group;
+	int i;
+
+	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++) {
+		struct list_head *discard_list = &discard_ctl->discard_list[i];
+
+		if (!list_empty(discard_list)) {
+			block_group = list_first_entry(discard_list,
+						       struct btrfs_block_group,
+						       discard_list);
+
+			if (!ret_block_group)
+				ret_block_group = block_group;
+
+			if (ret_block_group->discard_eligible_time < now)
+				break;
+
+			if (ret_block_group->discard_eligible_time >
+			    block_group->discard_eligible_time)
+				ret_block_group = block_group;
+		}
+	}
+
+	return ret_block_group;
+}
+
+/**
+ * peek_discard_list - wrap find_next_block_group()
+ * @discard_ctl: discard control
+ *
+ * This wraps find_next_block_group() and sets the block_group to be in use.
+ */
+static struct btrfs_block_group *peek_discard_list(
+					struct btrfs_discard_ctl *discard_ctl)
+{
+	struct btrfs_block_group *block_group;
+	u64 now = ktime_get_ns();
+
+	spin_lock(&discard_ctl->lock);
+
+	block_group = find_next_block_group(discard_ctl, now);
+
+	if (block_group && now < block_group->discard_eligible_time)
+		block_group = NULL;
+
+	discard_ctl->block_group = block_group;
+
+	spin_unlock(&discard_ctl->lock);
+
+	return block_group;
+}
+
+/**
+ * btrfs_discard_cancel_work - remove a block_group from the discard lists
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * This removes @block_group from the discard lists.  If necessary, it waits on
+ * the current work and then reschedules the delayed work.
+ */
+void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
+			       struct btrfs_block_group *block_group)
+{
+	if (remove_from_discard_list(discard_ctl, block_group)) {
+		cancel_delayed_work_sync(&discard_ctl->work);
+		btrfs_discard_schedule_work(discard_ctl, true);
+	}
+}
+
+/**
+ * btrfs_discard_queue_work - handles queuing the block_groups
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * This maintains the LRU order of the discard lists.
+ */
+void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
+			      struct btrfs_block_group *block_group)
+{
+	if (!block_group ||
+	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+		return;
+
+	btrfs_add_to_discard_list(discard_ctl, block_group);
+	if (!delayed_work_pending(&discard_ctl->work))
+		btrfs_discard_schedule_work(discard_ctl, false);
+}
+
+/**
+ * btrfs_discard_schedule_work - responsible for scheduling the discard work
+ * @discard_ctl: discard control
+ * @override: override the current timer
+ *
+ * Discards are issued by a delayed workqueue item.  @override is used to
+ * update the current delay as the baseline delay interview is reevaluated
+ * on transaction commit.  This is also maxed with any other rate limit.
+ */
+void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
+				 bool override)
+{
+	struct btrfs_block_group *block_group;
+	u64 now = ktime_get_ns();
+
+	spin_lock(&discard_ctl->lock);
+
+	if (!btrfs_run_discard_work(discard_ctl))
+		goto out;
+
+	if (!override && delayed_work_pending(&discard_ctl->work))
+		goto out;
+
+	block_group = find_next_block_group(discard_ctl, now);
+	if (block_group) {
+		u64 delay = 0;
+
+		if (now < block_group->discard_eligible_time)
+			delay = nsecs_to_jiffies(
+				block_group->discard_eligible_time - now);
+
+		mod_delayed_work(discard_ctl->discard_workers,
+				 &discard_ctl->work,
+				 delay);
+	}
+
+out:
+	spin_unlock(&discard_ctl->lock);
+}
+
+/**
+ * btrfs_discard_workfn - discard work function
+ * @work: work
+ *
+ * This finds the next block_group to start discarding and then discards it.
+ */
+static void btrfs_discard_workfn(struct work_struct *work)
+{
+	struct btrfs_discard_ctl *discard_ctl;
+	struct btrfs_block_group *block_group;
+	u64 trimmed = 0;
+
+	discard_ctl = container_of(work, struct btrfs_discard_ctl, work.work);
+
+	block_group = peek_discard_list(discard_ctl);
+	if (!block_group || !btrfs_run_discard_work(discard_ctl))
+		return;
+
+	btrfs_trim_block_group(block_group, &trimmed, block_group->start,
+			       btrfs_block_group_end(block_group), 0);
+
+	remove_from_discard_list(discard_ctl, block_group);
+
+	btrfs_discard_schedule_work(discard_ctl, false);
+}
+
+/**
+ * btrfs_run_discard_work - determines if async discard should be running
+ * @discard_ctl: discard control
+ *
+ * Checks if the file system is writeable and BTRFS_FS_DISCARD_RUNNING is set.
+ */
+bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl)
+{
+	struct btrfs_fs_info *fs_info = container_of(discard_ctl,
+						     struct btrfs_fs_info,
+						     discard_ctl);
+
+	return (!(fs_info->sb->s_flags & SB_RDONLY) &&
+		test_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags));
+}
+
+void btrfs_discard_resume(struct btrfs_fs_info *fs_info)
+{
+	if (!btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
+		btrfs_discard_cleanup(fs_info);
+		return;
+	}
+
+	set_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags);
+}
+
+void btrfs_discard_stop(struct btrfs_fs_info *fs_info)
+{
+	clear_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags);
+}
+
+void btrfs_discard_init(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	int i;
+
+	spin_lock_init(&discard_ctl->lock);
+
+	INIT_DELAYED_WORK(&discard_ctl->work, btrfs_discard_workfn);
+
+	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++)
+		INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
+}
+
+void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
+{
+	btrfs_discard_stop(fs_info);
+	cancel_delayed_work_sync(&fs_info->discard_ctl.work);
+}
diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
new file mode 100644
index 000000000000..439ca8c51877
--- /dev/null
+++ b/fs/btrfs/discard.h
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef BTRFS_DISCARD_H
+#define BTRFS_DISCARD_H
+
+struct btrfs_fs_info;
+struct btrfs_discard_ctl;
+struct btrfs_block_group;
+
+void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
+			       struct btrfs_block_group *block_group);
+
+void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
+			       struct btrfs_block_group *block_group);
+void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
+			      struct btrfs_block_group *block_group);
+void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
+				 bool override);
+bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl);
+
+void btrfs_discard_resume(struct btrfs_fs_info *fs_info);
+void btrfs_discard_stop(struct btrfs_fs_info *fs_info);
+void btrfs_discard_init(struct btrfs_fs_info *fs_info);
+void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info);
+
+#endif
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e0edfdc9c82b..8785b5c999b0 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -41,6 +41,7 @@
 #include "tree-checker.h"
 #include "ref-verify.h"
 #include "block-group.h"
+#include "discard.h"
 
 #define BTRFS_SUPER_FLAG_SUPP	(BTRFS_HEADER_FLAG_WRITTEN |\
 				 BTRFS_HEADER_FLAG_RELOC |\
@@ -1953,6 +1954,8 @@ static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
 	btrfs_destroy_workqueue(fs_info->readahead_workers);
 	btrfs_destroy_workqueue(fs_info->flush_workers);
 	btrfs_destroy_workqueue(fs_info->qgroup_rescan_workers);
+	if (fs_info->discard_ctl.discard_workers)
+		destroy_workqueue(fs_info->discard_ctl.discard_workers);
 	/*
 	 * Now that all other work queues are destroyed, we can safely destroy
 	 * the queues used for metadata I/O, since tasks from those other work
@@ -2148,6 +2151,8 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
 				      max_active, 2);
 	fs_info->qgroup_rescan_workers =
 		btrfs_alloc_workqueue(fs_info, "qgroup-rescan", flags, 1, 0);
+	fs_info->discard_ctl.discard_workers =
+		alloc_workqueue("btrfs_discard", WQ_UNBOUND | WQ_FREEZABLE, 1);
 
 	if (!(fs_info->workers && fs_info->delalloc_workers &&
 	      fs_info->flush_workers &&
@@ -2158,7 +2163,8 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
 	      fs_info->endio_freespace_worker && fs_info->rmw_workers &&
 	      fs_info->caching_workers && fs_info->readahead_workers &&
 	      fs_info->fixup_workers && fs_info->delayed_workers &&
-	      fs_info->qgroup_rescan_workers)) {
+	      fs_info->qgroup_rescan_workers &&
+	      fs_info->discard_ctl.discard_workers)) {
 		return -ENOMEM;
 	}
 
@@ -2793,6 +2799,8 @@ int __cold open_ctree(struct super_block *sb,
 	btrfs_init_dev_replace_locks(fs_info);
 	btrfs_init_qgroup(fs_info);
 
+	btrfs_discard_init(fs_info);
+
 	btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
 	btrfs_init_free_cluster(&fs_info->data_alloc_cluster);
 
@@ -3263,6 +3271,8 @@ int __cold open_ctree(struct super_block *sb,
 
 	btrfs_qgroup_rescan_resume(fs_info);
 
+	btrfs_discard_resume(fs_info);
+
 	if (!fs_info->uuid_root) {
 		btrfs_info(fs_info, "creating UUID tree");
 		ret = btrfs_create_uuid_tree(fs_info);
@@ -3954,6 +3964,9 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
 	 */
 	kthread_park(fs_info->cleaner_kthread);
 
+	/* cancel or finish ongoing work */
+	btrfs_discard_cleanup(fs_info);
+
 	/* wait for the qgroup rescan worker to stop */
 	btrfs_qgroup_wait_for_completion(fs_info, false);
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5dc696d0c5b2..857642dc8589 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -32,6 +32,7 @@
 #include "block-rsv.h"
 #include "delalloc-space.h"
 #include "block-group.h"
+#include "discard.h"
 
 #undef SCRAMBLE_DELAYED_REFS
 
@@ -2940,6 +2941,9 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 		cond_resched();
 	}
 
+	if (btrfs_test_opt(fs_info, DISCARD_ASYNC))
+		btrfs_discard_schedule_work(&fs_info->discard_ctl, true);
+
 	/*
 	 * Transaction is finished.  We don't need the lock anymore.  We
 	 * do need to clean up the block groups in case of a transaction
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 49ae1e6ee104..449bfaf6030f 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -21,6 +21,7 @@
 #include "space-info.h"
 #include "delalloc-space.h"
 #include "block-group.h"
+#include "discard.h"
 
 #define BITS_PER_BITMAP		(PAGE_SIZE * 8UL)
 #define MAX_CACHE_BYTES_PER_GIG	SZ_32K
@@ -755,9 +756,11 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 		/*
 		 * Sync discard ensures that the free space cache is always
 		 * trimmed.  So when reading this in, the state should reflect
-		 * that.
+		 * that.  We also do this for async as a stop gap for lack of
+		 * persistence.
 		 */
-		if (btrfs_test_opt(fs_info, DISCARD_SYNC))
+		if (btrfs_test_opt(fs_info, DISCARD_SYNC) ||
+		    btrfs_test_opt(fs_info, DISCARD_ASYNC))
 			e->trim_state = BTRFS_TRIM_STATE_TRIMMED;
 
 		if (!e->bytes) {
@@ -2382,6 +2385,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 			   u64 offset, u64 bytes,
 			   enum btrfs_trim_state trim_state)
 {
+	struct btrfs_block_group *block_group = ctl->private;
 	struct btrfs_free_space *info;
 	int ret = 0;
 
@@ -2431,6 +2435,9 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 		ASSERT(ret != -EEXIST);
 	}
 
+	if (trim_state != BTRFS_TRIM_STATE_TRIMMED)
+		btrfs_discard_queue_work(&fs_info->discard_ctl, block_group);
+
 	return ret;
 }
 
@@ -3204,6 +3211,7 @@ void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
 static int do_trimming(struct btrfs_block_group *block_group,
 		       u64 *total_trimmed, u64 start, u64 bytes,
 		       u64 reserved_start, u64 reserved_bytes,
+		       enum btrfs_trim_state reserved_trim_state,
 		       struct btrfs_trim_range *trim_entry)
 {
 	struct btrfs_space_info *space_info = block_group->space_info;
@@ -3211,6 +3219,9 @@ static int do_trimming(struct btrfs_block_group *block_group,
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	int ret;
 	int update = 0;
+	u64 end = start + bytes;
+	u64 reserved_end = reserved_start + reserved_bytes;
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 	u64 trimmed = 0;
 
 	spin_lock(&space_info->lock);
@@ -3224,11 +3235,20 @@ static int do_trimming(struct btrfs_block_group *block_group,
 	spin_unlock(&space_info->lock);
 
 	ret = btrfs_discard_extent(fs_info, start, bytes, &trimmed);
-	if (!ret)
+	if (!ret) {
 		*total_trimmed += trimmed;
+		trim_state = BTRFS_TRIM_STATE_TRIMMED;
+	}
 
 	mutex_lock(&ctl->cache_writeout_mutex);
-	btrfs_add_free_space(block_group, reserved_start, reserved_bytes);
+	if (reserved_start < start)
+		__btrfs_add_free_space(fs_info, ctl, reserved_start,
+				       start - reserved_start,
+				       reserved_trim_state);
+	if (start + bytes < reserved_start + reserved_bytes)
+		__btrfs_add_free_space(fs_info, ctl, end, reserved_end - end,
+				       reserved_trim_state);
+	__btrfs_add_free_space(fs_info, ctl, start, bytes, trim_state);
 	list_del(&trim_entry->list);
 	mutex_unlock(&ctl->cache_writeout_mutex);
 
@@ -3255,6 +3275,7 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 	int ret = 0;
 	u64 extent_start;
 	u64 extent_bytes;
+	enum btrfs_trim_state extent_trim_state;
 	u64 bytes;
 
 	while (start < end) {
@@ -3296,6 +3317,7 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 
 		extent_start = entry->offset;
 		extent_bytes = entry->bytes;
+		extent_trim_state = entry->trim_state;
 		start = max(start, extent_start);
 		bytes = min(extent_start + extent_bytes, end) - start;
 		if (bytes < minlen) {
@@ -3314,7 +3336,8 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 		mutex_unlock(&ctl->cache_writeout_mutex);
 
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
-				  extent_start, extent_bytes, &trim_entry);
+				  extent_start, extent_bytes, extent_trim_state,
+				  &trim_entry);
 		if (ret)
 			break;
 next:
@@ -3440,7 +3463,7 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		mutex_unlock(&ctl->cache_writeout_mutex);
 
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
-				  start, bytes, &trim_entry);
+				  start, bytes, 0, &trim_entry);
 		if (ret) {
 			reset_trimming_bitmap(ctl, offset);
 			break;
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f131fb9f0f69..0edf00753c00 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -46,6 +46,7 @@
 #include "sysfs.h"
 #include "tests/btrfs-tests.h"
 #include "block-group.h"
+#include "discard.h"
 
 #include "qgroup.h"
 #define CREATE_TRACE_POINTS
@@ -146,6 +147,8 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
 	if (sb_rdonly(sb))
 		return;
 
+	btrfs_discard_stop(fs_info);
+
 	/* btrfs handle error by forcing the filesystem readonly */
 	sb->s_flags |= SB_RDONLY;
 	btrfs_info(fs_info, "forced readonly");
@@ -313,6 +316,7 @@ enum {
 	Opt_datasum, Opt_nodatasum,
 	Opt_defrag, Opt_nodefrag,
 	Opt_discard, Opt_nodiscard,
+	Opt_discard_mode,
 	Opt_nologreplay,
 	Opt_norecovery,
 	Opt_ratio,
@@ -376,6 +380,7 @@ static const match_table_t tokens = {
 	{Opt_nodefrag, "noautodefrag"},
 	{Opt_discard, "discard"},
 	{Opt_nodiscard, "nodiscard"},
+	{Opt_discard_mode, "discard=%s"},
 	{Opt_nologreplay, "nologreplay"},
 	{Opt_norecovery, "norecovery"},
 	{Opt_ratio, "metadata_ratio=%u"},
@@ -695,12 +700,26 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 				   info->metadata_ratio);
 			break;
 		case Opt_discard:
-			btrfs_set_and_info(info, DISCARD_SYNC,
-					   "turning on sync discard");
+		case Opt_discard_mode:
+			if (token == Opt_discard ||
+			    strcmp(args[0].from, "sync") == 0) {
+				btrfs_clear_opt(info->mount_opt, DISCARD_ASYNC);
+				btrfs_set_and_info(info, DISCARD_SYNC,
+						   "turning on sync discard");
+			} else if (strcmp(args[0].from, "async") == 0) {
+				btrfs_clear_opt(info->mount_opt, DISCARD_SYNC);
+				btrfs_set_and_info(info, DISCARD_ASYNC,
+						   "turning on async discard");
+			} else {
+				ret = -EINVAL;
+				goto out;
+			}
 			break;
 		case Opt_nodiscard:
 			btrfs_clear_and_info(info, DISCARD_SYNC,
 					     "turning off discard");
+			btrfs_clear_and_info(info, DISCARD_ASYNC,
+					     "turning off async discard");
 			break;
 		case Opt_space_cache:
 		case Opt_space_cache_version:
@@ -1324,6 +1343,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",flushoncommit");
 	if (btrfs_test_opt(info, DISCARD_SYNC))
 		seq_puts(seq, ",discard");
+	if (btrfs_test_opt(info, DISCARD_ASYNC))
+		seq_puts(seq, ",discard=async");
 	if (!(info->sb->s_flags & SB_POSIXACL))
 		seq_puts(seq, ",noacl");
 	if (btrfs_test_opt(info, SPACE_CACHE))
@@ -1713,6 +1734,14 @@ static inline void btrfs_remount_cleanup(struct btrfs_fs_info *fs_info,
 		btrfs_cleanup_defrag_inodes(fs_info);
 	}
 
+	/* If we toggled discard async. */
+	if (!btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
+	    btrfs_test_opt(fs_info, DISCARD_ASYNC))
+		btrfs_discard_resume(fs_info);
+	else if (btrfs_raw_test_opt(old_opts, DISCARD_ASYNC) &&
+		 !btrfs_test_opt(fs_info, DISCARD_ASYNC))
+		btrfs_discard_cleanup(fs_info);
+
 	clear_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state);
 }
 
@@ -1760,6 +1789,8 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 		 */
 		cancel_work_sync(&fs_info->async_reclaim_work);
 
+		btrfs_discard_cleanup(fs_info);
+
 		/* wait for the uuid_scan task to finish */
 		down(&fs_info->uuid_tree_rescan_sem);
 		/* avoid complains from lockdep et al. */
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 06/22] btrfs: handle empty block_group removal
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (4 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 05/22] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 07/22] btrfs: discard one region at a time in async discard Dennis Zhou
                   ` (16 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

block_group removal is a little tricky. It can race with the extent
allocator, the cleaner thread, and balancing. The current path is for a
block_group to be added to the unused_bgs list. Then, when the cleaner
thread comes around, it starts a transaction and then proceeds with
removing the block_group. Extents that are pinned are subsequently
removed from the pinned trees and then eventually a discard is issued
for the entire block_group.

Async discard introduces another player into the game, the discard
workqueue. While it has none of the racing issues, the new problem is
ensuring we don't leave free space untrimmed prior to forgetting the
block_group.  This is handled by placing fully free block_groups on a
separate discard queue. This is necessary to maintain discarding order
as in the future we will slowly trim even fully free block_groups. The
ordering helps us make progress on the same block_group rather than say
the last fully freed block_group or needing to search through the fully
freed block groups at the beginning of a list and insert after.

The new order of events is a fully freed block group gets placed on the
unused discard queue first. Once it's processed, it will be placed on
the unusued_bgs list and then the original sequence of events will
happen, just without the final whole block_group discard.

The mount flags can change when processing unused_bgs, so when flipping
from DISCARD to DISCARD_ASYNC, the unused_bgs must be punted to the
discard_list to be trimmed. If we flip off DISCARD_ASYNC, we punt
free block groups on the discard_list to the unused_bg queue which will
do the final discard for us.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/block-group.c      |  50 +++++++++++++--
 fs/btrfs/ctree.h            |   9 ++-
 fs/btrfs/discard.c          | 117 +++++++++++++++++++++++++++++++++++-
 fs/btrfs/discard.h          |   6 ++
 fs/btrfs/free-space-cache.c |  34 +++++++++++
 fs/btrfs/free-space-cache.h |   1 +
 fs/btrfs/scrub.c            |   7 ++-
 7 files changed, 214 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index d2bc46c365f4..aea2b2637d65 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1250,6 +1250,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 	struct btrfs_block_group *block_group;
 	struct btrfs_space_info *space_info;
 	struct btrfs_trans_handle *trans;
+	bool async_trim_enabled = btrfs_test_opt(fs_info, DISCARD_ASYNC);
 	int ret = 0;
 
 	if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
@@ -1259,6 +1260,7 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 	while (!list_empty(&fs_info->unused_bgs)) {
 		u64 start, end;
 		int trimming;
+		bool async_trimmed;
 
 		block_group = list_first_entry(&fs_info->unused_bgs,
 					       struct btrfs_block_group,
@@ -1280,9 +1282,23 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		/* Don't want to race with allocators so take the groups_sem */
 		down_write(&space_info->groups_sem);
 		spin_lock(&block_group->lock);
+
+		/*
+		 * Async discard moves the final block group discard to be prior
+		 * to the unused_bgs code path.  Therefore, if it's not fully
+		 * trimmed, punt it back to the async discard lists.
+		 */
+		async_trimmed = (!btrfs_test_opt(fs_info, DISCARD_ASYNC) ||
+				 btrfs_is_free_space_trimmed(block_group));
+
 		if (block_group->reserved || block_group->pinned ||
 		    block_group->used || block_group->ro ||
-		    list_is_singular(&block_group->list)) {
+		    list_is_singular(&block_group->list) ||
+		    !async_trimmed) {
+			/* Requeue if we failed because of async discard. */
+			if (!async_trimmed)
+				btrfs_discard_queue_work(&fs_info->discard_ctl,
+							 block_group);
 			/*
 			 * We want to bail if we made new allocations or have
 			 * outstanding allocations in this block group.  We do
@@ -1365,6 +1381,17 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		spin_unlock(&block_group->lock);
 		spin_unlock(&space_info->lock);
 
+		/*
+		 * The normal path here is an unused block group is passed here,
+		 * then trimming is handled in the transaction commit path.
+		 * Async discard interposes before this to do the trimming
+		 * before coming down the unused block group path as trimming
+		 * will no longer be done later in the transaction commit path.
+		 */
+		if (!async_trim_enabled &&
+		    btrfs_test_opt(fs_info, DISCARD_ASYNC))
+			goto flip_async;
+
 		/* DISCARD can flip during remount */
 		trimming = btrfs_test_opt(fs_info, DISCARD_SYNC);
 
@@ -1409,6 +1436,13 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 		spin_lock(&fs_info->unused_bgs_lock);
 	}
 	spin_unlock(&fs_info->unused_bgs_lock);
+	return;
+
+flip_async:
+	btrfs_end_transaction(trans);
+	mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+	btrfs_put_block_group(block_group);
+	btrfs_discard_punt_unused_bgs_list(fs_info);
 }
 
 void btrfs_mark_bg_unused(struct btrfs_block_group *bg)
@@ -1613,6 +1647,8 @@ static struct btrfs_block_group *btrfs_create_block_group_cache(
 	cache->full_stripe_len = btrfs_full_stripe_len(fs_info, start);
 	set_free_space_tree_thresholds(cache);
 
+	cache->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
+
 	atomic_set(&cache->count, 1);
 	spin_lock_init(&cache->lock);
 	init_rwsem(&cache->data_rwsem);
@@ -1779,7 +1815,11 @@ static int read_one_block_group(struct btrfs_fs_info *info,
 		inc_block_group_ro(cache, 1);
 	} else if (cache->used == 0) {
 		ASSERT(list_empty(&cache->bg_list));
-		btrfs_mark_bg_unused(cache);
+		if (btrfs_test_opt(info, DISCARD_ASYNC))
+			btrfs_add_to_discard_unused_list(&info->discard_ctl,
+							 cache);
+		else
+			btrfs_mark_bg_unused(cache);
 	}
 	return 0;
 error:
@@ -2742,8 +2782,10 @@ int btrfs_update_block_group(struct btrfs_trans_handle *trans,
 		 * dirty list to avoid races between cleaner kthread and space
 		 * cache writeout.
 		 */
-		if (!alloc && old_val == 0)
-			btrfs_mark_bg_unused(cache);
+		if (!alloc && old_val == 0) {
+			if (!btrfs_test_opt(info, DISCARD_ASYNC))
+				btrfs_mark_bg_unused(cache);
+		}
 
 		btrfs_put_block_group(cache);
 		total -= num_bytes;
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d5ce8054f074..68340d65a8b6 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -443,9 +443,14 @@ struct btrfs_full_stripe_locks_tree {
 /* Discard control. */
 /*
  * Async discard uses multiple lists to differentiate the discard filter
- * parameters.
+ * parameters.  Index 0 is for completely free block groups where we need to
+ * ensure the entire block group is trimmed without being lossy.  Indices
+ * afterwards represent monotonically decreasing discard filter sizes to
+ * prioritize what should be discarded next.
  */
-#define BTRFS_NR_DISCARD_LISTS		1
+#define BTRFS_NR_DISCARD_LISTS		2
+#define BTRFS_DISCARD_INDEX_UNUSED	0
+#define BTRFS_DISCARD_INDEX_START	1
 
 struct btrfs_discard_ctl {
 	struct workqueue_struct *discard_workers;
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 15d54de3d682..e0f48d6de9a1 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -26,13 +26,33 @@ void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 {
 	spin_lock(&discard_ctl->lock);
 
-	if (list_empty(&block_group->discard_list))
+	if (list_empty(&block_group->discard_list) ||
+	    block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED) {
+		if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED)
+			block_group->discard_index = BTRFS_DISCARD_INDEX_START;
 		block_group->discard_eligible_time = (ktime_get_ns() +
 						      BTRFS_DISCARD_DELAY);
+	}
 
 	list_move_tail(&block_group->discard_list,
 		       btrfs_get_discard_list(discard_ctl, block_group));
 
+spin_unlock(&discard_ctl->lock);
+}
+
+void btrfs_add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
+				      struct btrfs_block_group *block_group)
+{
+	spin_lock(&discard_ctl->lock);
+
+	if (!list_empty(&block_group->discard_list))
+		list_del_init(&block_group->discard_list);
+
+	block_group->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
+	block_group->discard_eligible_time = ktime_get_ns();
+	list_add_tail(&block_group->discard_list,
+		      &discard_ctl->discard_list[BTRFS_DISCARD_INDEX_UNUSED]);
+
 	spin_unlock(&discard_ctl->lock);
 }
 
@@ -151,7 +171,11 @@ void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
 	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
 		return;
 
-	btrfs_add_to_discard_list(discard_ctl, block_group);
+	if (block_group->used == 0)
+		btrfs_add_to_discard_unused_list(discard_ctl, block_group);
+	else
+		btrfs_add_to_discard_list(discard_ctl, block_group);
+
 	if (!delayed_work_pending(&discard_ctl->work))
 		btrfs_discard_schedule_work(discard_ctl, false);
 }
@@ -196,6 +220,30 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
 	spin_unlock(&discard_ctl->lock);
 }
 
+/**
+ * btrfs_finish_discard_pass - determine next step of a block_group
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * This determines the next step for a block group after it's finished going
+ * through a pass on a discard list.  If it is unused and fully trimmed, we can
+ * mark it unused and send it to the unused_bgs path.  Otherwise, pass it onto
+ * the appropriate filter list or let it fall off.
+ */
+static void btrfs_finish_discard_pass(struct btrfs_discard_ctl *discard_ctl,
+				      struct btrfs_block_group *block_group)
+{
+	remove_from_discard_list(discard_ctl, block_group);
+
+	if (block_group->used == 0) {
+		if (btrfs_is_free_space_trimmed(block_group))
+			btrfs_mark_bg_unused(block_group);
+		else
+			btrfs_add_to_discard_unused_list(discard_ctl,
+							 block_group);
+	}
+}
+
 /**
  * btrfs_discard_workfn - discard work function
  * @work: work
@@ -217,7 +265,7 @@ static void btrfs_discard_workfn(struct work_struct *work)
 	btrfs_trim_block_group(block_group, &trimmed, block_group->start,
 			       btrfs_block_group_end(block_group), 0);
 
-	remove_from_discard_list(discard_ctl, block_group);
+	btrfs_finish_discard_pass(discard_ctl, block_group);
 
 	btrfs_discard_schedule_work(discard_ctl, false);
 }
@@ -238,6 +286,65 @@ bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl)
 		test_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags));
 }
 
+/**
+ * btrfs_discard_punt_unused_bgs_list - punt unused_bgs list to discard lists
+ * @fs_info: fs_info of interest
+ *
+ * The unused_bgs list needs to be punted to the discard lists because the
+ * order of operations is changed.  In the normal sychronous discard path, the
+ * block groups are trimmed via a single large trim in transaction commit.  This
+ * is ultimately what we are trying to avoid with asynchronous discard.  Thus,
+ * it must be done before going down the unused_bgs path.
+ */
+void btrfs_discard_punt_unused_bgs_list(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_block_group *block_group, *next;
+
+	spin_lock(&fs_info->unused_bgs_lock);
+
+	/* We enabled async discard, so punt all to the queue. */
+	list_for_each_entry_safe(block_group, next, &fs_info->unused_bgs,
+				 bg_list) {
+		list_del_init(&block_group->bg_list);
+		btrfs_add_to_discard_unused_list(&fs_info->discard_ctl,
+						 block_group);
+	}
+
+	spin_unlock(&fs_info->unused_bgs_lock);
+}
+
+/**
+ * btrfs_discard_purge_list - purge discard lists
+ * @discard_ctl: discard control
+ *
+ * If we are disabling async discard, we may have intercepted block groups that
+ * are completely free and ready for the unused_bgs path.  As discarding will
+ * now happen in transaction commit or not at all, we can safely mark the
+ * corresponding block groups as unused and they will be sent on their merry
+ * way to the unused_bgs list.
+ */
+static void btrfs_discard_purge_list(struct btrfs_discard_ctl *discard_ctl)
+{
+	struct btrfs_block_group *block_group, *next;
+	int i;
+
+	spin_lock(&discard_ctl->lock);
+
+	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++) {
+		list_for_each_entry_safe(block_group, next,
+					 &discard_ctl->discard_list[i],
+					 discard_list) {
+			list_del_init(&block_group->discard_list);
+			spin_unlock(&discard_ctl->lock);
+			if (block_group->used == 0)
+				btrfs_mark_bg_unused(block_group);
+			spin_lock(&discard_ctl->lock);
+		}
+	}
+
+	spin_unlock(&discard_ctl->lock);
+}
+
 void btrfs_discard_resume(struct btrfs_fs_info *fs_info)
 {
 	if (!btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
@@ -245,6 +352,8 @@ void btrfs_discard_resume(struct btrfs_fs_info *fs_info)
 		return;
 	}
 
+	btrfs_discard_punt_unused_bgs_list(fs_info);
+
 	set_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags);
 }
 
@@ -270,4 +379,6 @@ void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
 {
 	btrfs_discard_stop(fs_info);
 	cancel_delayed_work_sync(&fs_info->discard_ctl.work);
+
+	btrfs_discard_purge_list(&fs_info->discard_ctl);
 }
diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
index 439ca8c51877..b61ea684b48d 100644
--- a/fs/btrfs/discard.h
+++ b/fs/btrfs/discard.h
@@ -7,9 +7,13 @@ struct btrfs_fs_info;
 struct btrfs_discard_ctl;
 struct btrfs_block_group;
 
+/* List operations. */
 void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 			       struct btrfs_block_group *block_group);
+void btrfs_add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
+				      struct btrfs_block_group *block_group);
 
+/* Work operations. */
 void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
 			       struct btrfs_block_group *block_group);
 void btrfs_discard_queue_work(struct btrfs_discard_ctl *discard_ctl,
@@ -18,6 +22,8 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
 				 bool override);
 bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl);
 
+/* Setup/Cleanup operations. */
+void btrfs_discard_punt_unused_bgs_list(struct btrfs_fs_info *fs_info);
 void btrfs_discard_resume(struct btrfs_fs_info *fs_info);
 void btrfs_discard_stop(struct btrfs_fs_info *fs_info);
 void btrfs_discard_init(struct btrfs_fs_info *fs_info);
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 449bfaf6030f..7542bd349602 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2684,6 +2684,37 @@ void btrfs_remove_free_space_cache(struct btrfs_block_group *block_group)
 
 }
 
+/**
+ * btrfs_is_free_space_trimmed - see if everything is trimmed
+ * @block_group: block_group of interest
+ *
+ * Walk @block_group's free space rb_tree to determine if everything is trimmed.
+ */
+bool btrfs_is_free_space_trimmed(struct btrfs_block_group *block_group)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *info;
+	struct rb_node *node;
+	bool ret = true;
+
+	spin_lock(&ctl->tree_lock);
+	node = rb_first(&ctl->free_space_offset);
+
+	while (node) {
+		info = rb_entry(node, struct btrfs_free_space, offset_index);
+
+		if (!btrfs_free_space_trimmed(info)) {
+			ret = false;
+			break;
+		}
+
+		node = rb_next(node);
+	}
+
+	spin_unlock(&ctl->tree_lock);
+	return ret;
+}
+
 u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			       u64 offset, u64 bytes, u64 empty_size,
 			       u64 *max_extent_size)
@@ -2770,6 +2801,9 @@ int btrfs_return_cluster_to_free_space(
 	ret = __btrfs_return_cluster_to_free_space(block_group, cluster);
 	spin_unlock(&ctl->tree_lock);
 
+	btrfs_discard_queue_work(&block_group->fs_info->discard_ctl,
+				 block_group);
+
 	/* finally drop our ref */
 	btrfs_put_block_group(block_group);
 	return ret;
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 29d16f58b40b..49ff6d6f333b 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -117,6 +117,7 @@ int btrfs_remove_free_space(struct btrfs_block_group *block_group,
 			    u64 bytenr, u64 size);
 void __btrfs_remove_free_space_cache(struct btrfs_free_space_ctl *ctl);
 void btrfs_remove_free_space_cache(struct btrfs_block_group *block_group);
+bool btrfs_is_free_space_trimmed(struct btrfs_block_group *block_group);
 u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			       u64 offset, u64 bytes, u64 empty_size,
 			       u64 *max_extent_size);
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 21de630b0730..49b7afa38895 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -8,6 +8,7 @@
 #include <linux/sched/mm.h>
 #include <crypto/hash.h>
 #include "ctree.h"
+#include "discard.h"
 #include "volumes.h"
 #include "disk-io.h"
 #include "ordered-data.h"
@@ -3659,7 +3660,11 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
 		if (!cache->removed && !cache->ro && cache->reserved == 0 &&
 		    cache->used == 0) {
 			spin_unlock(&cache->lock);
-			btrfs_mark_bg_unused(cache);
+			if (btrfs_test_opt(fs_info, DISCARD_ASYNC))
+				btrfs_add_to_discard_unused_list(
+						&fs_info->discard_ctl, cache);
+			else
+				btrfs_mark_bg_unused(cache);
 		} else {
 			spin_unlock(&cache->lock);
 		}
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 07/22] btrfs: discard one region at a time in async discard
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (5 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 06/22] btrfs: handle empty block_group removal Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 08/22] btrfs: add removal calls for sysfs debug/ Dennis Zhou
                   ` (15 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

The prior two patches added discarding via a background workqueue. This
just piggybacked off of the fstrim code to trim the whole block at once.
Well inevitably this is worse performance wise and will aggressively
overtrim. But it was nice to plumb the other infrastructure to keep the
patches easier to review.

This adds the real goal of this series which is discarding slowly (ie a
slow long running fstrim). The discarding is split into two phases,
extents and then bitmaps. The reason for this is two fold. First, the
bitmap regions overlap the extent regions. Second, discarding the
extents first will let the newly trimmed bitmaps have the highest chance
of coalescing when being readded to the free space cache.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/block-group.h      |  15 +++++
 fs/btrfs/discard.c          |  81 ++++++++++++++++++----
 fs/btrfs/free-space-cache.c | 131 ++++++++++++++++++++++++++++--------
 fs/btrfs/free-space-cache.h |   6 ++
 4 files changed, 191 insertions(+), 42 deletions(-)

diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index 884defd61dcd..601e1d217e22 100644
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -12,6 +12,19 @@ enum btrfs_disk_cache_state {
 	BTRFS_DC_SETUP,
 };
 
+/*
+ * This describes the state of the block_group for async discard.  This is due
+ * to the two pass nature of it where extent discarding is prioritized over
+ * bitmap discarding.  BTRFS_DISCARD_RESET_CURSOR is set when we are resetting
+ * between lists to prevent contention for discard state variables
+ * (eg discard_cursor).
+ */
+enum btrfs_discard_state {
+	BTRFS_DISCARD_EXTENTS,
+	BTRFS_DISCARD_BITMAPS,
+	BTRFS_DISCARD_RESET_CURSOR,
+};
+
 /*
  * Control flags for do_chunk_alloc's force field CHUNK_ALLOC_NO_FORCE means to
  * only allocate a chunk if we really need one.
@@ -121,6 +134,8 @@ struct btrfs_block_group {
 	struct list_head discard_list;
 	int discard_index;
 	u64 discard_eligible_time;
+	u64 discard_cursor;
+	enum btrfs_discard_state discard_state;
 
 	/* For dirty block groups */
 	struct list_head dirty_list;
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index e0f48d6de9a1..8b676103919a 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -21,21 +21,28 @@ static struct list_head *btrfs_get_discard_list(
 	return &discard_ctl->discard_list[block_group->discard_index];
 }
 
-void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
-			       struct btrfs_block_group *block_group)
+static void __btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
+					struct btrfs_block_group *block_group)
 {
-	spin_lock(&discard_ctl->lock);
-
 	if (list_empty(&block_group->discard_list) ||
 	    block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED) {
 		if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED)
 			block_group->discard_index = BTRFS_DISCARD_INDEX_START;
 		block_group->discard_eligible_time = (ktime_get_ns() +
 						      BTRFS_DISCARD_DELAY);
+		block_group->discard_state = BTRFS_DISCARD_RESET_CURSOR;
 	}
 
 	list_move_tail(&block_group->discard_list,
 		       btrfs_get_discard_list(discard_ctl, block_group));
+}
+
+void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
+			       struct btrfs_block_group *block_group)
+{
+	spin_lock(&discard_ctl->lock);
+
+	__btrfs_add_to_discard_list(discard_ctl, block_group);
 
 spin_unlock(&discard_ctl->lock);
 }
@@ -50,6 +57,7 @@ void btrfs_add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
 
 	block_group->discard_index = BTRFS_DISCARD_INDEX_UNUSED;
 	block_group->discard_eligible_time = ktime_get_ns();
+	block_group->discard_state = BTRFS_DISCARD_RESET_CURSOR;
 	list_add_tail(&block_group->discard_list,
 		      &discard_ctl->discard_list[BTRFS_DISCARD_INDEX_UNUSED]);
 
@@ -117,23 +125,41 @@ static struct btrfs_block_group *find_next_block_group(
 /**
  * peek_discard_list - wrap find_next_block_group()
  * @discard_ctl: discard control
+ * @discard_state: the discard_state of the block_group after state management
  *
  * This wraps find_next_block_group() and sets the block_group to be in use.
+ * discard_state's control flow is managed here.  Variables related to
+ * discard_state are reset here as needed (eg discard_cursor).  @discard_state
+ * is remembered as it may change while we're discarding, but we want the
+ * discard to execute in the context determined here.
  */
 static struct btrfs_block_group *peek_discard_list(
-					struct btrfs_discard_ctl *discard_ctl)
+					struct btrfs_discard_ctl *discard_ctl,
+					enum btrfs_discard_state *discard_state)
 {
 	struct btrfs_block_group *block_group;
 	u64 now = ktime_get_ns();
 
 	spin_lock(&discard_ctl->lock);
 
+again:
 	block_group = find_next_block_group(discard_ctl, now);
 
-	if (block_group && now < block_group->discard_eligible_time)
+	if (block_group && now > block_group->discard_eligible_time) {
+		if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED &&
+		    block_group->used != 0) {
+			__btrfs_add_to_discard_list(discard_ctl, block_group);
+			goto again;
+		}
+		if (block_group->discard_state == BTRFS_DISCARD_RESET_CURSOR) {
+			block_group->discard_cursor = block_group->start;
+			block_group->discard_state = BTRFS_DISCARD_EXTENTS;
+		}
+		discard_ctl->block_group = block_group;
+		*discard_state = block_group->discard_state;
+	} else {
 		block_group = NULL;
-
-	discard_ctl->block_group = block_group;
+	}
 
 	spin_unlock(&discard_ctl->lock);
 
@@ -248,24 +274,53 @@ static void btrfs_finish_discard_pass(struct btrfs_discard_ctl *discard_ctl,
  * btrfs_discard_workfn - discard work function
  * @work: work
  *
- * This finds the next block_group to start discarding and then discards it.
+ * This finds the next block_group to start discarding and then discards a
+ * single region.  It does this in a two-pass fashion: first extents and second
+ * bitmaps.  Completely discarded block groups are sent to the unused_bgs path.
  */
 static void btrfs_discard_workfn(struct work_struct *work)
 {
 	struct btrfs_discard_ctl *discard_ctl;
 	struct btrfs_block_group *block_group;
+	enum btrfs_discard_state discard_state;
 	u64 trimmed = 0;
 
 	discard_ctl = container_of(work, struct btrfs_discard_ctl, work.work);
 
-	block_group = peek_discard_list(discard_ctl);
+	block_group = peek_discard_list(discard_ctl, &discard_state);
 	if (!block_group || !btrfs_run_discard_work(discard_ctl))
 		return;
 
-	btrfs_trim_block_group(block_group, &trimmed, block_group->start,
-			       btrfs_block_group_end(block_group), 0);
+	/* Perform discarding. */
+	if (discard_state == BTRFS_DISCARD_BITMAPS)
+		btrfs_trim_block_group_bitmaps(block_group, &trimmed,
+				       block_group->discard_cursor,
+				       btrfs_block_group_end(block_group),
+				       0, true);
+	else
+		btrfs_trim_block_group_extents(block_group, &trimmed,
+				       block_group->discard_cursor,
+				       btrfs_block_group_end(block_group),
+				       0, true);
+
+	/* Determine next steps for a block_group. */
+	if (block_group->discard_cursor >= btrfs_block_group_end(block_group)) {
+		if (discard_state == BTRFS_DISCARD_BITMAPS) {
+			btrfs_finish_discard_pass(discard_ctl, block_group);
+		} else {
+			block_group->discard_cursor = block_group->start;
+			spin_lock(&discard_ctl->lock);
+			if (block_group->discard_state !=
+			    BTRFS_DISCARD_RESET_CURSOR)
+				block_group->discard_state =
+							BTRFS_DISCARD_BITMAPS;
+			spin_unlock(&discard_ctl->lock);
+		}
+	}
 
-	btrfs_finish_discard_pass(discard_ctl, block_group);
+	spin_lock(&discard_ctl->lock);
+	discard_ctl->block_group = NULL;
+	spin_unlock(&discard_ctl->lock);
 
 	btrfs_discard_schedule_work(discard_ctl, false);
 }
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 7542bd349602..b1fdcc1ab36d 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3300,8 +3300,12 @@ static int do_trimming(struct btrfs_block_group *block_group,
 	return ret;
 }
 
+/*
+ * If @async is set, then we will trim 1 region and return.
+ */
 static int trim_no_bitmap(struct btrfs_block_group *block_group,
-			  u64 *total_trimmed, u64 start, u64 end, u64 minlen)
+			  u64 *total_trimmed, u64 start, u64 end, u64 minlen,
+			  bool async)
 {
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	struct btrfs_free_space *entry;
@@ -3318,36 +3322,25 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 		mutex_lock(&ctl->cache_writeout_mutex);
 		spin_lock(&ctl->tree_lock);
 
-		if (ctl->free_space < minlen) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			break;
-		}
+		if (ctl->free_space < minlen)
+			goto out_unlock;
 
 		entry = tree_search_offset(ctl, start, 0, 1);
-		if (!entry) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			break;
-		}
+		if (!entry)
+			goto out_unlock;
 
-		/* skip bitmaps */
-		while (entry->bitmap) {
+		/* skip bitmaps and if async, already trimmed entries */
+		while (entry->bitmap ||
+		       (async && btrfs_free_space_trimmed(entry))) {
 			node = rb_next(&entry->offset_index);
-			if (!node) {
-				spin_unlock(&ctl->tree_lock);
-				mutex_unlock(&ctl->cache_writeout_mutex);
-				goto out;
-			}
+			if (!node)
+				goto out_unlock;
 			entry = rb_entry(node, struct btrfs_free_space,
 					 offset_index);
 		}
 
-		if (entry->offset >= end) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			break;
-		}
+		if (entry->offset >= end)
+			goto out_unlock;
 
 		extent_start = entry->offset;
 		extent_bytes = entry->bytes;
@@ -3372,10 +3365,15 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
 				  extent_start, extent_bytes, extent_trim_state,
 				  &trim_entry);
-		if (ret)
+		if (ret) {
+			block_group->discard_cursor = start + bytes;
 			break;
+		}
 next:
 		start += bytes;
+		block_group->discard_cursor = start;
+		if (async && *total_trimmed)
+			break;
 
 		if (fatal_signal_pending(current)) {
 			ret = -ERESTARTSYS;
@@ -3384,7 +3382,14 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 
 		cond_resched();
 	}
-out:
+
+	return ret;
+
+out_unlock:
+	block_group->discard_cursor = btrfs_block_group_end(block_group);
+	spin_unlock(&ctl->tree_lock);
+	mutex_unlock(&ctl->cache_writeout_mutex);
+
 	return ret;
 }
 
@@ -3421,8 +3426,12 @@ static void end_trimming_bitmap(struct btrfs_free_space *entry)
 		entry->trim_state = BTRFS_TRIM_STATE_TRIMMED;
 }
 
+/*
+ * If @async is set, then we will trim 1 region and return.
+ */
 static int trim_bitmaps(struct btrfs_block_group *block_group,
-			u64 *total_trimmed, u64 start, u64 end, u64 minlen)
+			u64 *total_trimmed, u64 start, u64 end, u64 minlen,
+			bool async)
 {
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	struct btrfs_free_space *entry;
@@ -3439,13 +3448,16 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		spin_lock(&ctl->tree_lock);
 
 		if (ctl->free_space < minlen) {
+			block_group->discard_cursor =
+				btrfs_block_group_end(block_group);
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			break;
 		}
 
 		entry = tree_search_offset(ctl, offset, 1, 0);
-		if (!entry || btrfs_free_space_trimmed(entry)) {
+		if (!entry || (async && start == offset &&
+			       btrfs_free_space_trimmed(entry))) {
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			next_bitmap = true;
@@ -3478,6 +3490,16 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 			goto next;
 		}
 
+		/*
+		 * We already trimmed a region, but are using the locking above
+		 * to reset the trim_state.
+		 */
+		if (async && *total_trimmed) {
+			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
+			return ret;
+		}
+
 		bytes = min(bytes, end - start);
 		if (bytes < minlen) {
 			entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
@@ -3500,6 +3522,8 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 				  start, bytes, 0, &trim_entry);
 		if (ret) {
 			reset_trimming_bitmap(ctl, offset);
+			block_group->discard_cursor =
+				btrfs_block_group_end(block_group);
 			break;
 		}
 next:
@@ -3509,6 +3533,7 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		} else {
 			start += bytes;
 		}
+		block_group->discard_cursor = start;
 
 		if (fatal_signal_pending(current)) {
 			if (start != offset)
@@ -3520,6 +3545,9 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		cond_resched();
 	}
 
+	if (offset >= end)
+		block_group->discard_cursor = end;
+
 	return ret;
 }
 
@@ -3580,11 +3608,11 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 	btrfs_get_block_group_trimming(block_group);
 	spin_unlock(&block_group->lock);
 
-	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen);
+	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, false);
 	if (ret)
 		goto out;
 
-	ret = trim_bitmaps(block_group, trimmed, start, end, minlen);
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, false);
 	div64_u64_rem(end, BITS_PER_BITMAP * ctl->unit, &rem);
 	/* If we ended in the middle of a bitmap, reset the trimming flag. */
 	if (rem)
@@ -3594,6 +3622,51 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 	return ret;
 }
 
+int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   bool async)
+{
+	int ret;
+
+	*trimmed = 0;
+
+	spin_lock(&block_group->lock);
+	if (block_group->removed) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	btrfs_get_block_group_trimming(block_group);
+	spin_unlock(&block_group->lock);
+
+	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, async);
+
+	btrfs_put_block_group_trimming(block_group);
+	return ret;
+}
+
+int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   bool async)
+{
+	int ret;
+
+	*trimmed = 0;
+
+	spin_lock(&block_group->lock);
+	if (block_group->removed) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	btrfs_get_block_group_trimming(block_group);
+	spin_unlock(&block_group->lock);
+
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, async);
+
+	btrfs_put_block_group_trimming(block_group);
+	return ret;
+
+}
+
 /*
  * Find the left-most item in the cache tree, and then return the
  * smallest inode number in the item.
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 49ff6d6f333b..67b59ffd13e4 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -136,6 +136,12 @@ int btrfs_return_cluster_to_free_space(
 			       struct btrfs_free_cluster *cluster);
 int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 			   u64 *trimmed, u64 start, u64 end, u64 minlen);
+int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   bool async);
+int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   bool async);
 
 /* Support functions for running our sanity tests */
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 08/22] btrfs: add removal calls for sysfs debug/
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (6 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 07/22] btrfs: discard one region at a time in async discard Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 09/22] btrfs: make UUID/debug have its own kobject Dennis Zhou
                   ` (14 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

We probably should call sysfs_remove_group() on debug/.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/sysfs.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 5ebbe8a5ee76..58d089354bc1 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -771,6 +771,10 @@ void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info)
 		kobject_del(fs_info->space_info_kobj);
 		kobject_put(fs_info->space_info_kobj);
 	}
+#ifdef CONFIG_BTRFS_DEBUG
+	sysfs_remove_group(&fs_info->fs_devices->fsid_kobj,
+			   &btrfs_debug_feature_attr_group);
+#endif
 	addrm_unknown_feature_attrs(fs_info, false);
 	sysfs_remove_group(&fs_info->fs_devices->fsid_kobj, &btrfs_feature_attr_group);
 	sysfs_remove_files(&fs_info->fs_devices->fsid_kobj, btrfs_attrs);
@@ -1209,6 +1213,9 @@ void __cold btrfs_exit_sysfs(void)
 	sysfs_unmerge_group(&btrfs_kset->kobj,
 			    &btrfs_static_feature_attr_group);
 	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_feature_attr_group);
+#ifdef CONFIG_BTRFS_DEBUG
+	sysfs_remove_group(&btrfs_kset->kobj, &btrfs_debug_feature_attr_group);
+#endif
 	kset_unregister(btrfs_kset);
 }
 
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 09/22] btrfs: make UUID/debug have its own kobject
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (7 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 08/22] btrfs: add removal calls for sysfs debug/ Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 10/22] btrfs: add discard sysfs directory Dennis Zhou
                   ` (13 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Btrfs only allowed attributes to be exposed in debug/. Let's let other
groups be created by making debug its own kobject.

This also makes the per-fs debug options separate from the global
features mount attributes. This seems to be needed as
sysfs_create_files() requires const struct attribute * while
sysfs_create_group() can take struct attribute *. This seems nicer as
per file system, you'll probably use to_fs_info().

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h |  4 ++++
 fs/btrfs/sysfs.c | 20 ++++++++++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 68340d65a8b6..0c5cd5e6c2c5 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -927,6 +927,10 @@ struct btrfs_fs_info {
 	spinlock_t ref_verify_lock;
 	struct rb_root block_tree;
 #endif
+
+#ifdef CONFIG_BTRFS_DEBUG
+	struct kobject *debug_kobj;
+#endif
 };
 
 static inline struct btrfs_fs_info *btrfs_sb(struct super_block *sb)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 58d089354bc1..beae5c8146fb 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -344,6 +344,10 @@ static const struct attribute_group btrfs_static_feature_attr_group = {
  * /sys/fs/btrfs/debug - applies to module or all filesystems
  * /sys/fs/btrfs/UUID  - applies only to the given filesystem
  */
+static const struct attribute *btrfs_debug_mount_attrs[] = {
+	NULL,
+};
+
 static struct attribute *btrfs_debug_feature_attrs[] = {
 	NULL
 };
@@ -772,8 +776,12 @@ void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info)
 		kobject_put(fs_info->space_info_kobj);
 	}
 #ifdef CONFIG_BTRFS_DEBUG
-	sysfs_remove_group(&fs_info->fs_devices->fsid_kobj,
-			   &btrfs_debug_feature_attr_group);
+	if (fs_info->debug_kobj) {
+		sysfs_remove_files(fs_info->debug_kobj,
+				   btrfs_debug_mount_attrs);
+		kobject_del(fs_info->debug_kobj);
+		kobject_put(fs_info->debug_kobj);
+	}
 #endif
 	addrm_unknown_feature_attrs(fs_info, false);
 	sysfs_remove_group(&fs_info->fs_devices->fsid_kobj, &btrfs_feature_attr_group);
@@ -1115,8 +1123,12 @@ int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
 		goto failure;
 
 #ifdef CONFIG_BTRFS_DEBUG
-	error = sysfs_create_group(fsid_kobj,
-				   &btrfs_debug_feature_attr_group);
+	fs_info->debug_kobj = kobject_create_and_add("debug", fsid_kobj);
+	if (!fs_info->debug_kobj)
+		goto failure;
+
+	error = sysfs_create_files(fs_info->debug_kobj,
+				   btrfs_debug_mount_attrs);
 	if (error)
 		goto failure;
 #endif
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 10/22] btrfs: add discard sysfs directory
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (8 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 09/22] btrfs: make UUID/debug have its own kobject Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 11/22] btrfs: track discardable extents for async discard Dennis Zhou
                   ` (12 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Setup sysfs directory for discard stats + tunables.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h |  1 +
 fs/btrfs/sysfs.c | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 0c5cd5e6c2c5..6a547317d26f 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -930,6 +930,7 @@ struct btrfs_fs_info {
 
 #ifdef CONFIG_BTRFS_DEBUG
 	struct kobject *debug_kobj;
+	struct kobject *discard_debug_kobj;
 #endif
 };
 
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index beae5c8146fb..e877e4b3c631 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -338,6 +338,13 @@ static const struct attribute_group btrfs_static_feature_attr_group = {
 
 #ifdef CONFIG_BTRFS_DEBUG
 
+/*
+ * Discard statistics and tunables.
+ */
+static const struct attribute *discard_debug_attrs[] = {
+	NULL,
+};
+
 /*
  * Runtime debugging exported via sysfs
  *
@@ -776,6 +783,12 @@ void btrfs_sysfs_remove_mounted(struct btrfs_fs_info *fs_info)
 		kobject_put(fs_info->space_info_kobj);
 	}
 #ifdef CONFIG_BTRFS_DEBUG
+	if (fs_info->discard_debug_kobj) {
+		sysfs_remove_files(fs_info->discard_debug_kobj,
+				   discard_debug_attrs);
+		kobject_del(fs_info->discard_debug_kobj);
+		kobject_put(fs_info->discard_debug_kobj);
+	}
 	if (fs_info->debug_kobj) {
 		sysfs_remove_files(fs_info->debug_kobj,
 				   btrfs_debug_mount_attrs);
@@ -1131,6 +1144,19 @@ int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
 				   btrfs_debug_mount_attrs);
 	if (error)
 		goto failure;
+
+	/* Discard directory. */
+	fs_info->discard_debug_kobj = kobject_create_and_add("discard",
+						     fs_info->debug_kobj);
+	if (!fs_info->discard_debug_kobj) {
+		error = -ENOMEM;
+		goto failure;
+	}
+
+	error = sysfs_create_files(fs_info->discard_debug_kobj,
+				   discard_debug_attrs);
+	if (error)
+		goto failure;
 #endif
 
 	error = addrm_unknown_feature_attrs(fs_info, true);
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 11/22] btrfs: track discardable extents for async discard
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (9 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 10/22] btrfs: add discard sysfs directory Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 12/22] btrfs: keep track of discardable_bytes Dennis Zhou
                   ` (11 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

The number of discardable extents will serve as the rate limiting metric
for how often we should discard. This keeps track of discardable extents
in the free space caches by maintaining deltas and propagating them to
the global count.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/ctree.h            |  10 ++++
 fs/btrfs/discard.c          |  32 +++++++++++
 fs/btrfs/discard.h          |   4 ++
 fs/btrfs/free-space-cache.c | 106 +++++++++++++++++++++++++++++++++---
 fs/btrfs/free-space-cache.h |   2 +
 fs/btrfs/sysfs.c            |  15 +++++
 6 files changed, 160 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 6a547317d26f..c37533a8a313 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -101,6 +101,15 @@ struct btrfs_ref;
 
 #define BTRFS_MAX_EXTENT_SIZE SZ_128M
 
+/*
+ * Deltas are an effective way to populate global statistics.  Give macro names
+ * to make it clear what we're doing.  An example is discard_extents in
+ * btrfs_free_space_ctl.
+ */
+#define BTRFS_STAT_NR_ENTRIES	2
+#define BTRFS_STAT_CURR		0
+#define BTRFS_STAT_PREV		1
+
 
 /*
  * Count how many BTRFS_MAX_EXTENT_SIZE cover the @size
@@ -458,6 +467,7 @@ struct btrfs_discard_ctl {
 	spinlock_t lock;
 	struct btrfs_block_group *block_group;
 	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
+	atomic_t discardable_extents;
 };
 
 /* delayed seq elem */
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 8b676103919a..a05180af74e2 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -341,6 +341,36 @@ bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl)
 		test_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags));
 }
 
+/**
+ * btrfs_discard_update_discardable - propagate discard counters
+ * @block_group: block_group of interest
+ * @ctl: free_space_ctl of @block_group
+ *
+ * This propagates deltas of counters up to the discard_ctl.  It maintains a
+ * current counter and a previous counter passing the delta up to the global
+ * stat.  Then the current counter value becomes the previous counter value.
+ */
+void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
+				      struct btrfs_free_space_ctl *ctl)
+{
+	struct btrfs_discard_ctl *discard_ctl;
+	s32 extents_delta;
+
+	if (!block_group ||
+	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+		return;
+
+	discard_ctl = &block_group->fs_info->discard_ctl;
+
+	extents_delta = (ctl->discardable_extents[BTRFS_STAT_CURR] -
+			 ctl->discardable_extents[BTRFS_STAT_PREV]);
+	if (extents_delta) {
+		atomic_add(extents_delta, &discard_ctl->discardable_extents);
+		ctl->discardable_extents[BTRFS_STAT_PREV] =
+			ctl->discardable_extents[BTRFS_STAT_CURR];
+	}
+}
+
 /**
  * btrfs_discard_punt_unused_bgs_list - punt unused_bgs list to discard lists
  * @fs_info: fs_info of interest
@@ -428,6 +458,8 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
 
 	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++)
 		INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
+
+	atomic_set(&discard_ctl->discardable_extents, 0);
 }
 
 void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
index b61ea684b48d..75f00a84d540 100644
--- a/fs/btrfs/discard.h
+++ b/fs/btrfs/discard.h
@@ -22,6 +22,10 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
 				 bool override);
 bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl);
 
+/* Update operations. */
+void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
+				      struct btrfs_free_space_ctl *ctl);
+
 /* Setup/Cleanup operations. */
 void btrfs_discard_punt_unused_bgs_list(struct btrfs_fs_info *fs_info);
 void btrfs_discard_resume(struct btrfs_fs_info *fs_info);
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index b1fdcc1ab36d..d3848d86a674 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -32,6 +32,9 @@ struct btrfs_trim_range {
 	struct list_head list;
 };
 
+static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *bitmap_info);
+
 static int link_free_space(struct btrfs_free_space_ctl *ctl,
 			   struct btrfs_free_space *info);
 static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
@@ -816,12 +819,17 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 		ret = io_ctl_read_bitmap(&io_ctl, e);
 		if (ret)
 			goto free_cache;
+		e->bitmap_extents = count_bitmap_extents(ctl, e);
+		if (!btrfs_free_space_trimmed(e))
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				e->bitmap_extents;
 	}
 
 	io_ctl_drop_pages(&io_ctl);
 	merge_space_tree(ctl);
 	ret = 1;
 out:
+	btrfs_discard_update_discardable(ctl->private, ctl);
 	io_ctl_free(&io_ctl);
 	return ret;
 free_cache:
@@ -1635,6 +1643,9 @@ __unlink_free_space(struct btrfs_free_space_ctl *ctl,
 {
 	rb_erase(&info->offset_index, &ctl->free_space_offset);
 	ctl->free_extents--;
+
+	if (!info->bitmap && !btrfs_free_space_trimmed(info))
+		ctl->discardable_extents[BTRFS_STAT_CURR]--;
 }
 
 static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
@@ -1655,6 +1666,9 @@ static int link_free_space(struct btrfs_free_space_ctl *ctl,
 	if (ret)
 		return ret;
 
+	if (!info->bitmap && !btrfs_free_space_trimmed(info))
+		ctl->discardable_extents[BTRFS_STAT_CURR]++;
+
 	ctl->free_space += info->bytes;
 	ctl->free_extents++;
 	return ret;
@@ -1711,17 +1725,29 @@ static inline void __bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
 				       struct btrfs_free_space *info,
 				       u64 offset, u64 bytes)
 {
-	unsigned long start, count;
+	unsigned long start, count, end;
+	int extent_delta = -1;
 
 	start = offset_to_bit(info->offset, ctl->unit, offset);
 	count = bytes_to_bits(bytes, ctl->unit);
-	ASSERT(start + count <= BITS_PER_BITMAP);
+	end = start + count;
+	ASSERT(end <= BITS_PER_BITMAP);
 
 	bitmap_clear(info->bitmap, start, count);
 
 	info->bytes -= bytes;
 	if (info->max_extent_size > ctl->unit)
 		info->max_extent_size = 0;
+
+	if (start && test_bit(start - 1, info->bitmap))
+		extent_delta++;
+
+	if (end < BITS_PER_BITMAP && test_bit(end, info->bitmap))
+		extent_delta++;
+
+	info->bitmap_extents += extent_delta;
+	if (!btrfs_free_space_trimmed(info))
+		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
 }
 
 static void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
@@ -1736,16 +1762,28 @@ static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
 			    struct btrfs_free_space *info, u64 offset,
 			    u64 bytes)
 {
-	unsigned long start, count;
+	unsigned long start, count, end;
+	int extent_delta = 1;
 
 	start = offset_to_bit(info->offset, ctl->unit, offset);
 	count = bytes_to_bits(bytes, ctl->unit);
-	ASSERT(start + count <= BITS_PER_BITMAP);
+	end = start + count;
+	ASSERT(end <= BITS_PER_BITMAP);
 
 	bitmap_set(info->bitmap, start, count);
 
 	info->bytes += bytes;
 	ctl->free_space += bytes;
+
+	if (start && test_bit(start - 1, info->bitmap))
+		extent_delta--;
+
+	if (end < BITS_PER_BITMAP && test_bit(end, info->bitmap))
+		extent_delta--;
+
+	info->bitmap_extents += extent_delta;
+	if (!btrfs_free_space_trimmed(info))
+		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
 }
 
 /*
@@ -1881,11 +1919,35 @@ find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
 	return NULL;
 }
 
+static int count_bitmap_extents(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *bitmap_info)
+{
+	struct btrfs_block_group *block_group = ctl->private;
+	u64 bytes = bitmap_info->bytes;
+	unsigned int rs, re;
+	int count = 0;
+
+	if (!block_group || !bytes)
+		return count;
+
+	bitmap_for_each_set_region(bitmap_info->bitmap, rs, re, 0,
+				   BITS_PER_BITMAP) {
+		bytes -= (rs - re) * ctl->unit;
+		count++;
+
+		if (!bytes)
+			break;
+	}
+
+	return count;
+}
+
 static void add_new_bitmap(struct btrfs_free_space_ctl *ctl,
 			   struct btrfs_free_space *info, u64 offset)
 {
 	info->offset = offset_to_bitmap(ctl, offset);
 	info->bytes = 0;
+	info->bitmap_extents = 0;
 	INIT_LIST_HEAD(&info->list);
 	link_free_space(ctl, info);
 	ctl->total_bitmaps++;
@@ -1991,8 +2053,12 @@ static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
 	 * This is a tradeoff to make bitmap trim state minimal.  We mark the
 	 * whole bitmap untrimmed if at any point we add untrimmed regions.
 	 */
-	if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED)
+	if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED) {
+		if (btrfs_free_space_trimmed(info))
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				info->bitmap_extents;
 		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	}
 
 	end = info->offset + (u64)(BITS_PER_BITMAP * ctl->unit);
 
@@ -2428,6 +2494,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 	if (ret)
 		kmem_cache_free(btrfs_free_space_cachep, info);
 out:
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 
 	if (ret) {
@@ -2537,6 +2604,7 @@ int btrfs_remove_free_space(struct btrfs_block_group *block_group,
 		goto again;
 	}
 out_lock:
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 out:
 	return ret;
@@ -2622,8 +2690,16 @@ __btrfs_return_cluster_to_free_space(
 
 		bitmap = (entry->bitmap != NULL);
 		if (!bitmap) {
+			/* merging treats extents as if they were new */
+			if (!btrfs_free_space_trimmed(entry))
+				ctl->discardable_extents[BTRFS_STAT_CURR]--;
+
 			try_merge_free_space(ctl, entry, false);
 			steal_from_bitmap(ctl, entry, false);
+
+			/* as we insert directly, update these statistics */
+			if (!btrfs_free_space_trimmed(entry))
+				ctl->discardable_extents[BTRFS_STAT_CURR]++;
 		}
 		tree_insert_offset(&ctl->free_space_offset,
 				   entry->offset, &entry->offset_index, bitmap);
@@ -2680,6 +2756,7 @@ void btrfs_remove_free_space_cache(struct btrfs_block_group *block_group)
 		cond_resched_lock(&ctl->tree_lock);
 	}
 	__btrfs_remove_free_space_cache_locked(ctl);
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 
 }
@@ -2754,6 +2831,7 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			link_free_space(ctl, entry);
 	}
 out:
+	btrfs_discard_update_discardable(block_group, ctl);
 	spin_unlock(&ctl->tree_lock);
 
 	if (align_gap_len)
@@ -2919,6 +2997,8 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group *block_group,
 					entry->bitmap);
 			ctl->total_bitmaps--;
 			ctl->op->recalc_thresholds(ctl);
+		} else if (!btrfs_free_space_trimmed(entry)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR]--;
 		}
 		kmem_cache_free(btrfs_free_space_cachep, entry);
 	}
@@ -3414,16 +3494,24 @@ static void reset_trimming_bitmap(struct btrfs_free_space_ctl *ctl, u64 offset)
 	spin_lock(&ctl->tree_lock);
 
 	entry = tree_search_offset(ctl, offset, 1, 0);
-	if (entry)
+	if (entry) {
+		if (btrfs_free_space_trimmed(entry))
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				entry->bitmap_extents;
 		entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	}
 
 	spin_unlock(&ctl->tree_lock);
 }
 
-static void end_trimming_bitmap(struct btrfs_free_space *entry)
+static void end_trimming_bitmap(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *entry)
 {
-	if (btrfs_free_space_trimming_bitmap(entry))
+	if (btrfs_free_space_trimming_bitmap(entry)) {
 		entry->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+		ctl->discardable_extents[BTRFS_STAT_CURR] -=
+			entry->bitmap_extents;
+	}
 }
 
 /*
@@ -3481,7 +3569,7 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 			 * if BTRFS_TRIM_STATE_TRIMMED is set on a bitmap.
 			 */
 			if (ret2 && !minlen)
-				end_trimming_bitmap(entry);
+				end_trimming_bitmap(ctl, entry);
 			else
 				entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 			spin_unlock(&ctl->tree_lock);
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 67b59ffd13e4..56235391a04a 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -28,6 +28,7 @@ struct btrfs_free_space {
 	unsigned long *bitmap;
 	struct list_head list;
 	enum btrfs_trim_state trim_state;
+	s32 bitmap_extents;
 };
 
 static inline bool btrfs_free_space_trimmed(struct btrfs_free_space *info)
@@ -50,6 +51,7 @@ struct btrfs_free_space_ctl {
 	int total_bitmaps;
 	int unit;
 	u64 start;
+	s32 discardable_extents[BTRFS_STAT_NR_ENTRIES];
 	const struct btrfs_free_space_op *op;
 	void *private;
 	struct mutex cache_writeout_mutex;
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index e877e4b3c631..220d77c38363 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -12,6 +12,7 @@
 #include <crypto/hash.h>
 
 #include "ctree.h"
+#include "discard.h"
 #include "disk-io.h"
 #include "transaction.h"
 #include "sysfs.h"
@@ -341,7 +342,21 @@ static const struct attribute_group btrfs_static_feature_attr_group = {
 /*
  * Discard statistics and tunables.
  */
+#define discard_to_fs_info(_kobj)	to_fs_info((_kobj)->parent->parent)
+
+static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n",
+			atomic_read(&fs_info->discard_ctl.discardable_extents));
+}
+BTRFS_ATTR(discard, discardable_extents, btrfs_discardable_extents_show);
+
 static const struct attribute *discard_debug_attrs[] = {
+	BTRFS_ATTR_PTR(discard, discardable_extents),
 	NULL,
 };
 
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 12/22] btrfs: keep track of discardable_bytes
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (10 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 11/22] btrfs: track discardable extents for async discard Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 13/22] btrfs: calculate discard delay based on number of extents Dennis Zhou
                   ` (10 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Keep track of this metric so that we can understand how ahead or behind
we are in discarding rate.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/ctree.h            |  1 +
 fs/btrfs/discard.c          | 10 +++++++++
 fs/btrfs/free-space-cache.c | 41 +++++++++++++++++++++++++++++--------
 fs/btrfs/free-space-cache.h |  1 +
 fs/btrfs/sysfs.c            | 12 +++++++++++
 5 files changed, 56 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c37533a8a313..5b13bda52ab7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -468,6 +468,7 @@ struct btrfs_discard_ctl {
 	struct btrfs_block_group *block_group;
 	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
 	atomic_t discardable_extents;
+	atomic64_t discardable_bytes;
 };
 
 /* delayed seq elem */
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index a05180af74e2..074341c8242a 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -355,6 +355,7 @@ void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
 {
 	struct btrfs_discard_ctl *discard_ctl;
 	s32 extents_delta;
+	s64 bytes_delta;
 
 	if (!block_group ||
 	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
@@ -369,6 +370,14 @@ void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
 		ctl->discardable_extents[BTRFS_STAT_PREV] =
 			ctl->discardable_extents[BTRFS_STAT_CURR];
 	}
+
+	bytes_delta = (ctl->discardable_bytes[BTRFS_STAT_CURR] -
+		       ctl->discardable_bytes[BTRFS_STAT_PREV]);
+	if (bytes_delta) {
+		atomic64_add(bytes_delta, &discard_ctl->discardable_bytes);
+		ctl->discardable_bytes[BTRFS_STAT_PREV] =
+			ctl->discardable_bytes[BTRFS_STAT_CURR];
+	}
 }
 
 /**
@@ -460,6 +469,7 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
 		INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
 
 	atomic_set(&discard_ctl->discardable_extents, 0);
+	atomic64_set(&discard_ctl->discardable_bytes, 0);
 }
 
 void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index d3848d86a674..5655416f0ae7 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -820,9 +820,11 @@ static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
 		if (ret)
 			goto free_cache;
 		e->bitmap_extents = count_bitmap_extents(ctl, e);
-		if (!btrfs_free_space_trimmed(e))
+		if (!btrfs_free_space_trimmed(e)) {
 			ctl->discardable_extents[BTRFS_STAT_CURR] +=
 				e->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += e->bytes;
+		}
 	}
 
 	io_ctl_drop_pages(&io_ctl);
@@ -1644,8 +1646,10 @@ __unlink_free_space(struct btrfs_free_space_ctl *ctl,
 	rb_erase(&info->offset_index, &ctl->free_space_offset);
 	ctl->free_extents--;
 
-	if (!info->bitmap && !btrfs_free_space_trimmed(info))
+	if (!info->bitmap && !btrfs_free_space_trimmed(info)) {
 		ctl->discardable_extents[BTRFS_STAT_CURR]--;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= info->bytes;
+	}
 }
 
 static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
@@ -1666,8 +1670,10 @@ static int link_free_space(struct btrfs_free_space_ctl *ctl,
 	if (ret)
 		return ret;
 
-	if (!info->bitmap && !btrfs_free_space_trimmed(info))
+	if (!info->bitmap && !btrfs_free_space_trimmed(info)) {
 		ctl->discardable_extents[BTRFS_STAT_CURR]++;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] += info->bytes;
+	}
 
 	ctl->free_space += info->bytes;
 	ctl->free_extents++;
@@ -1746,8 +1752,10 @@ static inline void __bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
 		extent_delta++;
 
 	info->bitmap_extents += extent_delta;
-	if (!btrfs_free_space_trimmed(info))
+	if (!btrfs_free_space_trimmed(info)) {
 		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bytes;
+	}
 }
 
 static void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
@@ -1782,8 +1790,10 @@ static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
 		extent_delta--;
 
 	info->bitmap_extents += extent_delta;
-	if (!btrfs_free_space_trimmed(info))
+	if (!btrfs_free_space_trimmed(info)) {
 		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] += bytes;
+	}
 }
 
 /*
@@ -2054,9 +2064,11 @@ static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
 	 * whole bitmap untrimmed if at any point we add untrimmed regions.
 	 */
 	if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED) {
-		if (btrfs_free_space_trimmed(info))
+		if (btrfs_free_space_trimmed(info)) {
 			ctl->discardable_extents[BTRFS_STAT_CURR] +=
 				info->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += info->bytes;
+		}
 		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 	}
 
@@ -2691,15 +2703,21 @@ __btrfs_return_cluster_to_free_space(
 		bitmap = (entry->bitmap != NULL);
 		if (!bitmap) {
 			/* merging treats extents as if they were new */
-			if (!btrfs_free_space_trimmed(entry))
+			if (!btrfs_free_space_trimmed(entry)) {
 				ctl->discardable_extents[BTRFS_STAT_CURR]--;
+				ctl->discardable_bytes[BTRFS_STAT_CURR] -=
+					entry->bytes;
+			}
 
 			try_merge_free_space(ctl, entry, false);
 			steal_from_bitmap(ctl, entry, false);
 
 			/* as we insert directly, update these statistics */
-			if (!btrfs_free_space_trimmed(entry))
+			if (!btrfs_free_space_trimmed(entry)) {
 				ctl->discardable_extents[BTRFS_STAT_CURR]++;
+				ctl->discardable_bytes[BTRFS_STAT_CURR] +=
+					entry->bytes;
+			}
 		}
 		tree_insert_offset(&ctl->free_space_offset,
 				   entry->offset, &entry->offset_index, bitmap);
@@ -2990,6 +3008,8 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group *block_group,
 	spin_lock(&ctl->tree_lock);
 
 	ctl->free_space -= bytes;
+	if (!entry->bitmap && !btrfs_free_space_trimmed(entry))
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bytes;
 	if (entry->bytes == 0) {
 		ctl->free_extents--;
 		if (entry->bitmap) {
@@ -3495,9 +3515,11 @@ static void reset_trimming_bitmap(struct btrfs_free_space_ctl *ctl, u64 offset)
 
 	entry = tree_search_offset(ctl, offset, 1, 0);
 	if (entry) {
-		if (btrfs_free_space_trimmed(entry))
+		if (btrfs_free_space_trimmed(entry)) {
 			ctl->discardable_extents[BTRFS_STAT_CURR] +=
 				entry->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += entry->bytes;
+		}
 		entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
 	}
 
@@ -3511,6 +3533,7 @@ static void end_trimming_bitmap(struct btrfs_free_space_ctl *ctl,
 		entry->trim_state = BTRFS_TRIM_STATE_TRIMMED;
 		ctl->discardable_extents[BTRFS_STAT_CURR] -=
 			entry->bitmap_extents;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= entry->bytes;
 	}
 }
 
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 56235391a04a..b61b52eeaaf3 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -52,6 +52,7 @@ struct btrfs_free_space_ctl {
 	int unit;
 	u64 start;
 	s32 discardable_extents[BTRFS_STAT_NR_ENTRIES];
+	s64 discardable_bytes[BTRFS_STAT_NR_ENTRIES];
 	const struct btrfs_free_space_op *op;
 	void *private;
 	struct mutex cache_writeout_mutex;
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 220d77c38363..07098f6d62bd 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -355,8 +355,20 @@ static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
 }
 BTRFS_ATTR(discard, discardable_extents, btrfs_discardable_extents_show);
 
+static ssize_t btrfs_discardable_bytes_show(struct kobject *kobj,
+					    struct kobj_attribute *a,
+					    char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+			atomic64_read(&fs_info->discard_ctl.discardable_bytes));
+}
+BTRFS_ATTR(discard, discardable_bytes, btrfs_discardable_bytes_show);
+
 static const struct attribute *discard_debug_attrs[] = {
 	BTRFS_ATTR_PTR(discard, discardable_extents),
+	BTRFS_ATTR_PTR(discard, discardable_bytes),
 	NULL,
 };
 
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 13/22] btrfs: calculate discard delay based on number of extents
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (11 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 12/22] btrfs: keep track of discardable_bytes Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 14/22] btrfs: add bps discard rate limit Dennis Zhou
                   ` (9 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Use the number of discardable extents to help guide our discard delay
interval. This value is reevaluated every transaction commit.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h       |  2 ++
 fs/btrfs/discard.c     | 53 ++++++++++++++++++++++++++++++++++++++----
 fs/btrfs/discard.h     |  1 +
 fs/btrfs/extent-tree.c |  4 +++-
 fs/btrfs/sysfs.c       | 31 ++++++++++++++++++++++++
 5 files changed, 86 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 5b13bda52ab7..78b970cfd108 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -469,6 +469,8 @@ struct btrfs_discard_ctl {
 	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
 	atomic_t discardable_extents;
 	atomic64_t discardable_bytes;
+	u32 delay;
+	u32 iops_limit;
 };
 
 /* delayed seq elem */
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 074341c8242a..ddd5cc303b1e 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -14,6 +14,11 @@
 /* This is an initial delay to give some chance for lba reuse. */
 #define BTRFS_DISCARD_DELAY		(120ULL * NSEC_PER_SEC)
 
+/* Target completion latency of discarding all discardable extents. */
+#define BTRFS_DISCARD_TARGET_MSEC	(6 * 60 * 60UL * MSEC_PER_SEC)
+#define BTRFS_DISCARD_MAX_DELAY		(10000UL)
+#define BTRFS_DISCARD_MAX_IOPS		(10UL)
+
 static struct list_head *btrfs_get_discard_list(
 					struct btrfs_discard_ctl *discard_ctl,
 					struct btrfs_block_group *block_group)
@@ -231,11 +236,18 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
 
 	block_group = find_next_block_group(discard_ctl, now);
 	if (block_group) {
-		u64 delay = 0;
+		u32 delay = discard_ctl->delay;
+
+		/*
+		 * This timeout is to hopefully prevent immediate discarding
+		 * in a recently allocated block group.
+		 */
+		if (now < block_group->discard_eligible_time) {
+			u64 bg_timeout = (block_group->discard_eligible_time -
+					  now);
 
-		if (now < block_group->discard_eligible_time)
-			delay = nsecs_to_jiffies(
-				block_group->discard_eligible_time - now);
+			delay = max_t(u64, delay, nsecs_to_jiffies(bg_timeout));
+		}
 
 		mod_delayed_work(discard_ctl->discard_workers,
 				 &discard_ctl->work,
@@ -341,6 +353,37 @@ bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl)
 		test_bit(BTRFS_FS_DISCARD_RUNNING, &fs_info->flags));
 }
 
+/**
+ * btrfs_discard_calc_delay - recalculate the base delay
+ * @discard_ctl: discard control
+ *
+ * Recalculate the base delay which is based off the total number of
+ * discardable_extents.  Clamp this with the iops_limit and
+ * BTRFS_DISCARD_MAX_DELAY.
+ */
+void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl)
+{
+	s32 discardable_extents =
+		atomic_read(&discard_ctl->discardable_extents);
+	s32 iops_limit;
+	unsigned long delay;
+
+	if (!discardable_extents)
+		return;
+
+	spin_lock(&discard_ctl->lock);
+
+	iops_limit = READ_ONCE(discard_ctl->iops_limit);
+	if (iops_limit)
+		iops_limit = MSEC_PER_SEC / iops_limit;
+
+	delay = BTRFS_DISCARD_TARGET_MSEC / discardable_extents;
+	delay = clamp_t(s32, delay, iops_limit, BTRFS_DISCARD_MAX_DELAY);
+	discard_ctl->delay = msecs_to_jiffies(delay);
+
+	spin_unlock(&discard_ctl->lock);
+}
+
 /**
  * btrfs_discard_update_discardable - propagate discard counters
  * @block_group: block_group of interest
@@ -470,6 +513,8 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
 
 	atomic_set(&discard_ctl->discardable_extents, 0);
 	atomic64_set(&discard_ctl->discardable_bytes, 0);
+	discard_ctl->delay = BTRFS_DISCARD_MAX_DELAY;
+	discard_ctl->iops_limit = BTRFS_DISCARD_MAX_IOPS;
 }
 
 void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
index 75f00a84d540..88f1363aa4e4 100644
--- a/fs/btrfs/discard.h
+++ b/fs/btrfs/discard.h
@@ -23,6 +23,7 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
 bool btrfs_run_discard_work(struct btrfs_discard_ctl *discard_ctl);
 
 /* Update operations. */
+void btrfs_discard_calc_delay(struct btrfs_discard_ctl *discard_ctl);
 void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
 				      struct btrfs_free_space_ctl *ctl);
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 857642dc8589..27ca833c11c8 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2941,8 +2941,10 @@ int btrfs_finish_extent_commit(struct btrfs_trans_handle *trans)
 		cond_resched();
 	}
 
-	if (btrfs_test_opt(fs_info, DISCARD_ASYNC))
+	if (btrfs_test_opt(fs_info, DISCARD_ASYNC)) {
+		btrfs_discard_calc_delay(&fs_info->discard_ctl);
 		btrfs_discard_schedule_work(&fs_info->discard_ctl, true);
+	}
 
 	/*
 	 * Transaction is finished.  We don't need the lock anymore.  We
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 07098f6d62bd..043430ae3818 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -344,6 +344,36 @@ static const struct attribute_group btrfs_static_feature_attr_group = {
  */
 #define discard_to_fs_info(_kobj)	to_fs_info((_kobj)->parent->parent)
 
+static ssize_t btrfs_discard_iops_limit_show(struct kobject *kobj,
+					     struct kobj_attribute *a,
+					     char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%u\n",
+			READ_ONCE(fs_info->discard_ctl.iops_limit));
+}
+
+static ssize_t btrfs_discard_iops_limit_store(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	u32 iops_limit;
+	int ret;
+
+	ret = kstrtou32(buf, 10, &iops_limit);
+	if (ret)
+		return -EINVAL;
+
+	WRITE_ONCE(discard_ctl->iops_limit, iops_limit);
+
+	return len;
+}
+BTRFS_ATTR_RW(discard, iops_limit, btrfs_discard_iops_limit_show,
+	      btrfs_discard_iops_limit_store);
+
 static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
 					      struct kobj_attribute *a,
 					      char *buf)
@@ -367,6 +397,7 @@ static ssize_t btrfs_discardable_bytes_show(struct kobject *kobj,
 BTRFS_ATTR(discard, discardable_bytes, btrfs_discardable_bytes_show);
 
 static const struct attribute *discard_debug_attrs[] = {
+	BTRFS_ATTR_PTR(discard, iops_limit),
 	BTRFS_ATTR_PTR(discard, discardable_extents),
 	BTRFS_ATTR_PTR(discard, discardable_bytes),
 	NULL,
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 14/22] btrfs: add bps discard rate limit
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (12 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 13/22] btrfs: calculate discard delay based on number of extents Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
                   ` (8 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Provide an ability to rate limit based on mbps in addition to the iops
delay calculated from number of discardable extents.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/ctree.h   |  2 ++
 fs/btrfs/discard.c | 18 ++++++++++++++++++
 fs/btrfs/sysfs.c   | 31 +++++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 78b970cfd108..303f000fe30a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -467,10 +467,12 @@ struct btrfs_discard_ctl {
 	spinlock_t lock;
 	struct btrfs_block_group *block_group;
 	struct list_head discard_list[BTRFS_NR_DISCARD_LISTS];
+	u64 prev_discard;
 	atomic_t discardable_extents;
 	atomic64_t discardable_bytes;
 	u32 delay;
 	u32 iops_limit;
+	u64 bps_limit;
 };
 
 /* delayed seq elem */
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index ddd5cc303b1e..49e148a6a0ea 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -4,6 +4,7 @@
 #include <linux/kernel.h>
 #include <linux/ktime.h>
 #include <linux/list.h>
+#include <linux/math64.h>
 #include <linux/sizes.h>
 #include <linux/workqueue.h>
 #include "ctree.h"
@@ -237,6 +238,19 @@ void btrfs_discard_schedule_work(struct btrfs_discard_ctl *discard_ctl,
 	block_group = find_next_block_group(discard_ctl, now);
 	if (block_group) {
 		u32 delay = discard_ctl->delay;
+		u64 bps_limit = READ_ONCE(discard_ctl->bps_limit);
+
+		/*
+		 * A single delayed workqueue item is responsible for
+		 * discarding, so we can manage the bytes rate limit by keeping
+		 * track of the previous discard.
+		 */
+		if (bps_limit && discard_ctl->prev_discard) {
+			u64 bps_delay = div64_u64(discard_ctl->prev_discard *
+						  MSEC_PER_SEC, bps_limit);
+
+			delay = max_t(u64, delay, msecs_to_jiffies(bps_delay));
+		}
 
 		/*
 		 * This timeout is to hopefully prevent immediate discarding
@@ -315,6 +329,8 @@ static void btrfs_discard_workfn(struct work_struct *work)
 				       btrfs_block_group_end(block_group),
 				       0, true);
 
+	discard_ctl->prev_discard = trimmed;
+
 	/* Determine next steps for a block_group. */
 	if (block_group->discard_cursor >= btrfs_block_group_end(block_group)) {
 		if (discard_state == BTRFS_DISCARD_BITMAPS) {
@@ -511,10 +527,12 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
 	for (i = 0; i < BTRFS_NR_DISCARD_LISTS; i++)
 		INIT_LIST_HEAD(&discard_ctl->discard_list[i]);
 
+	discard_ctl->prev_discard = 0;
 	atomic_set(&discard_ctl->discardable_extents, 0);
 	atomic64_set(&discard_ctl->discardable_bytes, 0);
 	discard_ctl->delay = BTRFS_DISCARD_MAX_DELAY;
 	discard_ctl->iops_limit = BTRFS_DISCARD_MAX_IOPS;
+	discard_ctl->bps_limit = 0;
 }
 
 void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 043430ae3818..028081bdde6c 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -374,6 +374,36 @@ static ssize_t btrfs_discard_iops_limit_store(struct kobject *kobj,
 BTRFS_ATTR_RW(discard, iops_limit, btrfs_discard_iops_limit_show,
 	      btrfs_discard_iops_limit_store);
 
+static ssize_t btrfs_discard_bps_limit_show(struct kobject *kobj,
+					    struct kobj_attribute *a,
+					    char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%llu\n",
+			READ_ONCE(fs_info->discard_ctl.bps_limit));
+}
+
+static ssize_t btrfs_discard_bps_limit_store(struct kobject *kobj,
+					     struct kobj_attribute *a,
+					     const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	u64 bps_limit;
+	int ret;
+
+	ret = kstrtou64(buf, 10, &bps_limit);
+	if (ret)
+		return -EINVAL;
+
+	WRITE_ONCE(discard_ctl->bps_limit, bps_limit);
+
+	return len;
+}
+BTRFS_ATTR_RW(discard, bps_limit, btrfs_discard_bps_limit_show,
+	      btrfs_discard_bps_limit_store);
+
 static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
 					      struct kobj_attribute *a,
 					      char *buf)
@@ -398,6 +428,7 @@ BTRFS_ATTR(discard, discardable_bytes, btrfs_discardable_bytes_show);
 
 static const struct attribute *discard_debug_attrs[] = {
 	BTRFS_ATTR_PTR(discard, iops_limit),
+	BTRFS_ATTR_PTR(discard, bps_limit),
 	BTRFS_ATTR_PTR(discard, discardable_extents),
 	BTRFS_ATTR_PTR(discard, discardable_bytes),
 	NULL,
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 15/22] btrfs: limit max discard size for async discard
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (13 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 14/22] btrfs: add bps discard rate limit Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 16/22] btrfs: make max async discard size tunable Dennis Zhou
                   ` (7 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Throttle the maximum size of a discard so that we can provide an upper
bound for the rate of async discard. While the block layer is able to
split discards into the appropriate sized discards, we want to be able
to account more accurately the rate at which we are consuming ncq slots
as well as limit the upper bound of work for a discard.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/discard.h          |  5 ++++
 fs/btrfs/free-space-cache.c | 48 +++++++++++++++++++++++++++----------
 2 files changed, 41 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
index 88f1363aa4e4..e1819f319901 100644
--- a/fs/btrfs/discard.h
+++ b/fs/btrfs/discard.h
@@ -3,10 +3,15 @@
 #ifndef BTRFS_DISCARD_H
 #define BTRFS_DISCARD_H
 
+#include <linux/sizes.h>
+
 struct btrfs_fs_info;
 struct btrfs_discard_ctl;
 struct btrfs_block_group;
 
+/* Discard size limits. */
+#define BTRFS_ASYNC_DISCARD_MAX_SIZE	(SZ_64M)
+
 /* List operations. */
 void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 			       struct btrfs_block_group *block_group);
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 5655416f0ae7..452afd616623 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3442,19 +3442,40 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 		if (entry->offset >= end)
 			goto out_unlock;
 
-		extent_start = entry->offset;
-		extent_bytes = entry->bytes;
-		extent_trim_state = entry->trim_state;
-		start = max(start, extent_start);
-		bytes = min(extent_start + extent_bytes, end) - start;
-		if (bytes < minlen) {
-			spin_unlock(&ctl->tree_lock);
-			mutex_unlock(&ctl->cache_writeout_mutex);
-			goto next;
-		}
+		if (async) {
+			start = extent_start = entry->offset;
+			bytes = extent_bytes = entry->bytes;
+			extent_trim_state = entry->trim_state;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
+			unlink_free_space(ctl, entry);
+			if (bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE) {
+				bytes = extent_bytes =
+					BTRFS_ASYNC_DISCARD_MAX_SIZE;
+				entry->offset += BTRFS_ASYNC_DISCARD_MAX_SIZE;
+				entry->bytes -= BTRFS_ASYNC_DISCARD_MAX_SIZE;
+				link_free_space(ctl, entry);
+			} else {
+				kmem_cache_free(btrfs_free_space_cachep, entry);
+			}
+		} else {
+			extent_start = entry->offset;
+			extent_bytes = entry->bytes;
+			extent_trim_state = entry->trim_state;
+			start = max(start, extent_start);
+			bytes = min(extent_start + extent_bytes, end) - start;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
 
-		unlink_free_space(ctl, entry);
-		kmem_cache_free(btrfs_free_space_cachep, entry);
+			unlink_free_space(ctl, entry);
+			kmem_cache_free(btrfs_free_space_cachep, entry);
+		}
 
 		spin_unlock(&ctl->tree_lock);
 		trim_entry.start = extent_start;
@@ -3619,6 +3640,9 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 			goto next;
 		}
 
+		if (async && bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE)
+			bytes = BTRFS_ASYNC_DISCARD_MAX_SIZE;
+
 		bitmap_clear_bits(ctl, entry, start, bytes);
 		if (entry->bytes == 0)
 			free_bitmap(ctl, entry);
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 16/22] btrfs: make max async discard size tunable
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (14 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
                   ` (6 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Expose max_discard_size as a tunable via sysfs.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
 fs/btrfs/ctree.h            |  1 +
 fs/btrfs/discard.c          |  1 +
 fs/btrfs/free-space-cache.c | 19 ++++++++++++-------
 fs/btrfs/sysfs.c            | 31 +++++++++++++++++++++++++++++++
 4 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 303f000fe30a..37ad60913092 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -470,6 +470,7 @@ struct btrfs_discard_ctl {
 	u64 prev_discard;
 	atomic_t discardable_extents;
 	atomic64_t discardable_bytes;
+	u64 max_discard_size;
 	u32 delay;
 	u32 iops_limit;
 	u64 bps_limit;
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 49e148a6a0ea..93e632267247 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -530,6 +530,7 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
 	discard_ctl->prev_discard = 0;
 	atomic_set(&discard_ctl->discardable_extents, 0);
 	atomic64_set(&discard_ctl->discardable_bytes, 0);
+	discard_ctl->max_discard_size = BTRFS_ASYNC_DISCARD_MAX_SIZE;
 	discard_ctl->delay = BTRFS_DISCARD_MAX_DELAY;
 	discard_ctl->iops_limit = BTRFS_DISCARD_MAX_IOPS;
 	discard_ctl->bps_limit = 0;
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 452afd616623..1c195308652d 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -3407,6 +3407,8 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 			  u64 *total_trimmed, u64 start, u64 end, u64 minlen,
 			  bool async)
 {
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	struct btrfs_free_space *entry;
 	struct rb_node *node;
@@ -3415,6 +3417,7 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 	u64 extent_bytes;
 	enum btrfs_trim_state extent_trim_state;
 	u64 bytes;
+	u64 max_discard_size = READ_ONCE(discard_ctl->max_discard_size);
 
 	while (start < end) {
 		struct btrfs_trim_range trim_entry;
@@ -3452,11 +3455,10 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 				goto next;
 			}
 			unlink_free_space(ctl, entry);
-			if (bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE) {
-				bytes = extent_bytes =
-					BTRFS_ASYNC_DISCARD_MAX_SIZE;
-				entry->offset += BTRFS_ASYNC_DISCARD_MAX_SIZE;
-				entry->bytes -= BTRFS_ASYNC_DISCARD_MAX_SIZE;
+			if (max_discard_size && bytes > max_discard_size) {
+				bytes = extent_bytes = max_discard_size;
+				entry->offset += max_discard_size;
+				entry->bytes -= max_discard_size;
 				link_free_space(ctl, entry);
 			} else {
 				kmem_cache_free(btrfs_free_space_cachep, entry);
@@ -3565,12 +3567,15 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 			u64 *total_trimmed, u64 start, u64 end, u64 minlen,
 			bool async)
 {
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	struct btrfs_free_space *entry;
 	int ret = 0;
 	int ret2;
 	u64 bytes;
 	u64 offset = offset_to_bitmap(ctl, start);
+	u64 max_discard_size = READ_ONCE(discard_ctl->max_discard_size);
 
 	while (offset < end) {
 		bool next_bitmap = false;
@@ -3640,8 +3645,8 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 			goto next;
 		}
 
-		if (async && bytes > BTRFS_ASYNC_DISCARD_MAX_SIZE)
-			bytes = BTRFS_ASYNC_DISCARD_MAX_SIZE;
+		if (async && max_discard_size && bytes > max_discard_size)
+			bytes = max_discard_size;
 
 		bitmap_clear_bits(ctl, entry, start, bytes);
 		if (entry->bytes == 0)
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 028081bdde6c..65417a66866d 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -404,6 +404,36 @@ static ssize_t btrfs_discard_bps_limit_store(struct kobject *kobj,
 BTRFS_ATTR_RW(discard, bps_limit, btrfs_discard_bps_limit_show,
 	      btrfs_discard_bps_limit_store);
 
+static ssize_t btrfs_discard_max_discard_size_show(struct kobject *kobj,
+						   struct kobj_attribute *a,
+						   char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%llu\n",
+			READ_ONCE(fs_info->discard_ctl.max_discard_size));
+}
+
+static ssize_t btrfs_discard_max_discard_size_store(struct kobject *kobj,
+						    struct kobj_attribute *a,
+						    const char *buf, size_t len)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+	struct btrfs_discard_ctl *discard_ctl = &fs_info->discard_ctl;
+	u64 max_discard_size;
+	int ret;
+
+	ret = kstrtou64(buf, 10, &max_discard_size);
+	if (ret)
+		return -EINVAL;
+
+	WRITE_ONCE(discard_ctl->max_discard_size, max_discard_size);
+
+	return len;
+}
+BTRFS_ATTR_RW(discard, max_discard_size, btrfs_discard_max_discard_size_show,
+	      btrfs_discard_max_discard_size_store);
+
 static ssize_t btrfs_discardable_extents_show(struct kobject *kobj,
 					      struct kobj_attribute *a,
 					      char *buf)
@@ -429,6 +459,7 @@ BTRFS_ATTR(discard, discardable_bytes, btrfs_discardable_bytes_show);
 static const struct attribute *discard_debug_attrs[] = {
 	BTRFS_ATTR_PTR(discard, iops_limit),
 	BTRFS_ATTR_PTR(discard, bps_limit),
+	BTRFS_ATTR_PTR(discard, max_discard_size),
 	BTRFS_ATTR_PTR(discard, discardable_extents),
 	BTRFS_ATTR_PTR(discard, discardable_bytes),
 	NULL,
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 17/22] btrfs: have multiple discard lists
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (15 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 16/22] btrfs: make max async discard size tunable Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
                   ` (5 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Non-block group destruction discarding currently only had a single list
with no minimum discard length. This can lead to caravaning more
meaningful discards behind a heavily fragmented block group.

This adds support for multiple lists with minimum discard lengths to
prevent the caravan effect. We promote block groups back up when we
exceed the BTRFS_ASYNC_DISCARD_MAX_FILTER size, currently we support
only 2 lists with filters of 1MB and 32KB respectively.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h            |   2 +-
 fs/btrfs/discard.c          | 101 +++++++++++++++++++++++++++++++++---
 fs/btrfs/discard.h          |   4 ++
 fs/btrfs/free-space-cache.c |  53 ++++++++++++++-----
 fs/btrfs/free-space-cache.h |   2 +-
 5 files changed, 139 insertions(+), 23 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 37ad60913092..52f69aaaa19c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -457,7 +457,7 @@ struct btrfs_full_stripe_locks_tree {
  * afterwards represent monotonically decreasing discard filter sizes to
  * prioritize what should be discarded next.
  */
-#define BTRFS_NR_DISCARD_LISTS		2
+#define BTRFS_NR_DISCARD_LISTS		3
 #define BTRFS_DISCARD_INDEX_UNUSED	0
 #define BTRFS_DISCARD_INDEX_START	1
 
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 93e632267247..004d83b0a215 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -20,6 +20,10 @@
 #define BTRFS_DISCARD_MAX_DELAY		(10000UL)
 #define BTRFS_DISCARD_MAX_IOPS		(10UL)
 
+/* Montonically decreasing minimum length filters after index 0. */
+static int discard_minlen[BTRFS_NR_DISCARD_LISTS] = {0,
+	BTRFS_ASYNC_DISCARD_MAX_FILTER, BTRFS_ASYNC_DISCARD_MIN_FILTER};
+
 static struct list_head *btrfs_get_discard_list(
 					struct btrfs_discard_ctl *discard_ctl,
 					struct btrfs_block_group *block_group)
@@ -132,16 +136,18 @@ static struct btrfs_block_group *find_next_block_group(
  * peek_discard_list - wrap find_next_block_group()
  * @discard_ctl: discard control
  * @discard_state: the discard_state of the block_group after state management
+ * @discard_index: the discard_index of the block_group after state management
  *
  * This wraps find_next_block_group() and sets the block_group to be in use.
  * discard_state's control flow is managed here.  Variables related to
  * discard_state are reset here as needed (eg discard_cursor).  @discard_state
- * is remembered as it may change while we're discarding, but we want the
- * discard to execute in the context determined here.
+ * and @discard_index are remembered as it may change while we're discarding,
+ * but we want the discard to execute in the context determined here.
  */
 static struct btrfs_block_group *peek_discard_list(
 					struct btrfs_discard_ctl *discard_ctl,
-					enum btrfs_discard_state *discard_state)
+					enum btrfs_discard_state *discard_state,
+					int *discard_index)
 {
 	struct btrfs_block_group *block_group;
 	u64 now = ktime_get_ns();
@@ -163,6 +169,7 @@ static struct btrfs_block_group *peek_discard_list(
 		}
 		discard_ctl->block_group = block_group;
 		*discard_state = block_group->discard_state;
+		*discard_index = block_group->discard_index;
 	} else {
 		block_group = NULL;
 	}
@@ -172,6 +179,65 @@ static struct btrfs_block_group *peek_discard_list(
 	return block_group;
 }
 
+/**
+ * btrfs_discard_check_filter - updates a block groups filters
+ * @block_group: block group of interest
+ * @bytes: recently freed region size after coalescing
+ *
+ * Async discard maintains multiple lists with progressively smaller filters
+ * to prioritize discarding based on size.  Should a free space that matches
+ * a larger filter be returned to the free_space_cache, prioritize that discard
+ * by moving @block_group to the proper filter.
+ */
+void btrfs_discard_check_filter(struct btrfs_block_group *block_group,
+				u64 bytes)
+{
+	struct btrfs_discard_ctl *discard_ctl;
+
+	if (!block_group ||
+	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+		return;
+
+	discard_ctl = &block_group->fs_info->discard_ctl;
+
+	if (block_group->discard_index > BTRFS_DISCARD_INDEX_START &&
+	    bytes >= discard_minlen[block_group->discard_index - 1]) {
+		int i;
+
+		remove_from_discard_list(discard_ctl, block_group);
+
+		for (i = BTRFS_DISCARD_INDEX_START; i < BTRFS_NR_DISCARD_LISTS;
+		     i++) {
+			if (bytes >= discard_minlen[i]) {
+				block_group->discard_index = i;
+				btrfs_add_to_discard_list(discard_ctl,
+							  block_group);
+				break;
+			}
+		}
+	}
+}
+
+/**
+ * btrfs_update_discard_index - moves a block_group along the discard lists
+ * @discard_ctl: discard control
+ * @block_group: block_group of interest
+ *
+ * Increment @block_group's discard_index.  If it falls of the list, let it be.
+ * Otherwise add it back to the appropriate list.
+ */
+static void btrfs_update_discard_index(struct btrfs_discard_ctl *discard_ctl,
+				       struct btrfs_block_group *block_group)
+{
+	block_group->discard_index++;
+	if (block_group->discard_index == BTRFS_NR_DISCARD_LISTS) {
+		block_group->discard_index = 1;
+		return;
+	}
+
+	btrfs_add_to_discard_list(discard_ctl, block_group);
+}
+
 /**
  * btrfs_discard_cancel_work - remove a block_group from the discard lists
  * @discard_ctl: discard control
@@ -293,6 +359,8 @@ static void btrfs_finish_discard_pass(struct btrfs_discard_ctl *discard_ctl,
 		else
 			btrfs_add_to_discard_unused_list(discard_ctl,
 							 block_group);
+	} else {
+		btrfs_update_discard_index(discard_ctl, block_group);
 	}
 }
 
@@ -309,25 +377,42 @@ static void btrfs_discard_workfn(struct work_struct *work)
 	struct btrfs_discard_ctl *discard_ctl;
 	struct btrfs_block_group *block_group;
 	enum btrfs_discard_state discard_state;
+	int discard_index = 0;
 	u64 trimmed = 0;
+	u64 minlen = 0;
 
 	discard_ctl = container_of(work, struct btrfs_discard_ctl, work.work);
 
-	block_group = peek_discard_list(discard_ctl, &discard_state);
+	block_group = peek_discard_list(discard_ctl, &discard_state,
+					&discard_index);
 	if (!block_group || !btrfs_run_discard_work(discard_ctl))
 		return;
 
 	/* Perform discarding. */
-	if (discard_state == BTRFS_DISCARD_BITMAPS)
+	minlen = discard_minlen[discard_index];
+
+	if (discard_state == BTRFS_DISCARD_BITMAPS) {
+		u64 maxlen = 0;
+
+		/*
+		 * Use the previous levels minimum discard length as the max
+		 * length filter.  In the case something is added to make a
+		 * region go beyond the max filter, the entire bitmap is set
+		 * back to BTRFS_TRIM_STATE_UNTRIMMED.
+		 */
+		if (discard_index != BTRFS_DISCARD_INDEX_UNUSED)
+			maxlen = discard_minlen[discard_index - 1];
+
 		btrfs_trim_block_group_bitmaps(block_group, &trimmed,
 				       block_group->discard_cursor,
 				       btrfs_block_group_end(block_group),
-				       0, true);
-	else
+				       minlen, maxlen, true);
+	} else {
 		btrfs_trim_block_group_extents(block_group, &trimmed,
 				       block_group->discard_cursor,
 				       btrfs_block_group_end(block_group),
-				       0, true);
+				       minlen, true);
+	}
 
 	discard_ctl->prev_discard = trimmed;
 
diff --git a/fs/btrfs/discard.h b/fs/btrfs/discard.h
index e1819f319901..9dbc25bede08 100644
--- a/fs/btrfs/discard.h
+++ b/fs/btrfs/discard.h
@@ -11,12 +11,16 @@ struct btrfs_block_group;
 
 /* Discard size limits. */
 #define BTRFS_ASYNC_DISCARD_MAX_SIZE	(SZ_64M)
+#define BTRFS_ASYNC_DISCARD_MAX_FILTER	(SZ_1M)
+#define BTRFS_ASYNC_DISCARD_MIN_FILTER	(SZ_32K)
 
 /* List operations. */
 void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 			       struct btrfs_block_group *block_group);
 void btrfs_add_to_discard_unused_list(struct btrfs_discard_ctl *discard_ctl,
 				      struct btrfs_block_group *block_group);
+void btrfs_discard_check_filter(struct btrfs_block_group *block_group,
+				u64 bytes);
 
 /* Work operations. */
 void btrfs_discard_cancel_work(struct btrfs_discard_ctl *discard_ctl,
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 1c195308652d..83398c42213f 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2466,6 +2466,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 	struct btrfs_block_group *block_group = ctl->private;
 	struct btrfs_free_space *info;
 	int ret = 0;
+	u64 filter_bytes = bytes;
 
 	info = kmem_cache_zalloc(btrfs_free_space_cachep, GFP_NOFS);
 	if (!info)
@@ -2502,6 +2503,8 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 	 */
 	steal_from_bitmap(ctl, info, true);
 
+	filter_bytes = max(filter_bytes, info->bytes);
+
 	ret = link_free_space(ctl, info);
 	if (ret)
 		kmem_cache_free(btrfs_free_space_cachep, info);
@@ -2514,8 +2517,10 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info,
 		ASSERT(ret != -EEXIST);
 	}
 
-	if (trim_state != BTRFS_TRIM_STATE_TRIMMED)
+	if (trim_state != BTRFS_TRIM_STATE_TRIMMED) {
+		btrfs_discard_check_filter(block_group, filter_bytes);
 		btrfs_discard_queue_work(&fs_info->discard_ctl, block_group);
+	}
 
 	return ret;
 }
@@ -3455,7 +3460,14 @@ static int trim_no_bitmap(struct btrfs_block_group *block_group,
 				goto next;
 			}
 			unlink_free_space(ctl, entry);
-			if (max_discard_size && bytes > max_discard_size) {
+			/*
+			 * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+			 * If X < BTRFS_ASYNC_DISCARD_MIN_FILTER, we won't trim
+			 * X when we come back around.  So trim it now.
+			 */
+			if (max_discard_size &&
+			    bytes >= (max_discard_size +
+				      BTRFS_ASYNC_DISCARD_MIN_FILTER)) {
 				bytes = extent_bytes = max_discard_size;
 				entry->offset += max_discard_size;
 				entry->bytes -= max_discard_size;
@@ -3565,7 +3577,7 @@ static void end_trimming_bitmap(struct btrfs_free_space_ctl *ctl,
  */
 static int trim_bitmaps(struct btrfs_block_group *block_group,
 			u64 *total_trimmed, u64 start, u64 end, u64 minlen,
-			bool async)
+			u64 maxlen, bool async)
 {
 	struct btrfs_discard_ctl *discard_ctl =
 					&block_group->fs_info->discard_ctl;
@@ -3593,7 +3605,15 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		}
 
 		entry = tree_search_offset(ctl, offset, 1, 0);
-		if (!entry || (async && start == offset &&
+		/*
+		 * Bitmaps are marked trimmed lossily now to prevent constant
+		 * discarding of the same bitmap (the reason why we are bound
+		 * by the filters).  So, retrim the block group bitmaps when we
+		 * are preparing to punt to the unused_bgs list.  This uses
+		 * @minlen to determine if we are in BTRFS_DISCARD_INDEX_UNUSED
+		 * which is the only discard index which sets minlen to 0.
+		 */
+		if (!entry || (async && minlen && start == offset &&
 			       btrfs_free_space_trimmed(entry))) {
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
@@ -3614,10 +3634,10 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
 		if (ret2 || start >= end) {
 			/*
-			 * This keeps the invariant that all bytes are trimmed
-			 * if BTRFS_TRIM_STATE_TRIMMED is set on a bitmap.
+			 * We lossily consider a bitmap trimmed if we only skip
+			 * over regions <= BTRFS_ASYNC_DISCARD_MIN_FILTER.
 			 */
-			if (ret2 && !minlen)
+			if (ret2 && minlen <= BTRFS_ASYNC_DISCARD_MIN_FILTER)
 				end_trimming_bitmap(ctl, entry);
 			else
 				entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
@@ -3638,14 +3658,20 @@ static int trim_bitmaps(struct btrfs_block_group *block_group,
 		}
 
 		bytes = min(bytes, end - start);
-		if (bytes < minlen) {
-			entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+		if (bytes < minlen || (async && maxlen && bytes > maxlen)) {
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
 			goto next;
 		}
 
-		if (async && max_discard_size && bytes > max_discard_size)
+		/*
+		 * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+		 * If X < @minlen, we won't trim X when we come back around.
+		 * So trim it now.  We differ here from trimming extents as we
+		 * don't keep individual state per bit.
+		 */
+		if (async && max_discard_size &&
+		    bytes > (max_discard_size + minlen))
 			bytes = max_discard_size;
 
 		bitmap_clear_bits(ctl, entry, start, bytes);
@@ -3752,7 +3778,7 @@ int btrfs_trim_block_group(struct btrfs_block_group *block_group,
 	if (ret)
 		goto out;
 
-	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, false);
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, 0, false);
 	div64_u64_rem(end, BITS_PER_BITMAP * ctl->unit, &rem);
 	/* If we ended in the middle of a bitmap, reset the trimming flag. */
 	if (rem)
@@ -3786,7 +3812,7 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
 
 int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
 				   u64 *trimmed, u64 start, u64 end, u64 minlen,
-				   bool async)
+				   u64 maxlen, bool async)
 {
 	int ret;
 
@@ -3800,7 +3826,8 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
 	btrfs_get_block_group_trimming(block_group);
 	spin_unlock(&block_group->lock);
 
-	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, async);
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, maxlen,
+			   async);
 
 	btrfs_put_block_group_trimming(block_group);
 	return ret;
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index b61b52eeaaf3..7c6d95765979 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -144,7 +144,7 @@ int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
 				   bool async);
 int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
 				   u64 *trimmed, u64 start, u64 end, u64 minlen,
-				   bool async);
+				   u64 maxlen, bool async);
 
 /* Support functions for running our sanity tests */
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 18/22] btrfs: only keep track of data extents for async discard
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (16 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:46 ` [PATCH 19/22] btrfs: keep track of discard reuse stats Dennis Zhou
                   ` (4 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

As mentioned earlier, discarding data can be done either by issuing an
explicit discard or implicitly by reusing the LBA. Metadata chunks see
much more frequent reuse due to well it being metadata. So instead of
explicitly discarding metadata blocks, just leave them be and let the
latter implicit discarding be done for them.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/block-group.h |  6 ++++++
 fs/btrfs/discard.c     | 12 ++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index 601e1d217e22..ee8441439a56 100644
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -182,6 +182,12 @@ static inline u64 btrfs_block_group_end(struct btrfs_block_group *block_group)
 	return (block_group->start + block_group->length);
 }
 
+static inline bool btrfs_is_block_group_data(
+					struct btrfs_block_group *block_group)
+{
+	return (block_group->flags & BTRFS_BLOCK_GROUP_DATA);
+}
+
 #ifdef CONFIG_BTRFS_DEBUG
 static inline int btrfs_should_fragment_free_space(
 		struct btrfs_block_group *block_group)
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 004d83b0a215..c8e923b3f2b9 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -50,6 +50,9 @@ static void __btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 void btrfs_add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 			       struct btrfs_block_group *block_group)
 {
+	if (!btrfs_is_block_group_data(block_group))
+		return;
+
 	spin_lock(&discard_ctl->lock);
 
 	__btrfs_add_to_discard_list(discard_ctl, block_group);
@@ -160,7 +163,11 @@ static struct btrfs_block_group *peek_discard_list(
 	if (block_group && now > block_group->discard_eligible_time) {
 		if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED &&
 		    block_group->used != 0) {
-			__btrfs_add_to_discard_list(discard_ctl, block_group);
+			if (btrfs_is_block_group_data(block_group))
+				__btrfs_add_to_discard_list(discard_ctl,
+							    block_group);
+			else
+				list_del_init(&block_group->discard_list);
 			goto again;
 		}
 		if (block_group->discard_state == BTRFS_DISCARD_RESET_CURSOR) {
@@ -502,7 +509,8 @@ void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
 	s64 bytes_delta;
 
 	if (!block_group ||
-	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+	    !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC) ||
+	    !btrfs_is_block_group_data(block_group))
 		return;
 
 	discard_ctl = &block_group->fs_info->discard_ctl;
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 19/22] btrfs: keep track of discard reuse stats
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (17 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
@ 2019-11-25 19:46 ` Dennis Zhou
  2019-11-25 19:47 ` [PATCH 20/22] btrfs: add async discard header Dennis Zhou
                   ` (3 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:46 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Keep track of how much we are discarding and how often we are reusing
with async discard.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h            |  3 +++
 fs/btrfs/discard.c          |  7 +++++++
 fs/btrfs/free-space-cache.c | 14 ++++++++++++++
 fs/btrfs/sysfs.c            | 36 ++++++++++++++++++++++++++++++++++++
 4 files changed, 60 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 52f69aaaa19c..dc0007368791 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -474,6 +474,9 @@ struct btrfs_discard_ctl {
 	u32 delay;
 	u32 iops_limit;
 	u64 bps_limit;
+	u64 discard_extent_bytes;
+	u64 discard_bitmap_bytes;
+	atomic64_t discard_bytes_saved;
 };
 
 /* delayed seq elem */
diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index c8e923b3f2b9..7ab4a93fc3b7 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -414,11 +414,15 @@ static void btrfs_discard_workfn(struct work_struct *work)
 				       block_group->discard_cursor,
 				       btrfs_block_group_end(block_group),
 				       minlen, maxlen, true);
+		WRITE_ONCE(discard_ctl->discard_bitmap_bytes,
+			   discard_ctl->discard_bitmap_bytes + trimmed);
 	} else {
 		btrfs_trim_block_group_extents(block_group, &trimmed,
 				       block_group->discard_cursor,
 				       btrfs_block_group_end(block_group),
 				       minlen, true);
+		WRITE_ONCE(discard_ctl->discard_extent_bytes,
+			   discard_ctl->discard_extent_bytes + trimmed);
 	}
 
 	discard_ctl->prev_discard = trimmed;
@@ -627,6 +631,9 @@ void btrfs_discard_init(struct btrfs_fs_info *fs_info)
 	discard_ctl->delay = BTRFS_DISCARD_MAX_DELAY;
 	discard_ctl->iops_limit = BTRFS_DISCARD_MAX_IOPS;
 	discard_ctl->bps_limit = 0;
+	discard_ctl->discard_extent_bytes = 0;
+	discard_ctl->discard_bitmap_bytes = 0;
+	atomic64_set(&discard_ctl->discard_bytes_saved, 0);
 }
 
 void btrfs_discard_cleanup(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 83398c42213f..1b887c0d7508 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2820,6 +2820,8 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			       u64 *max_extent_size)
 {
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space *entry = NULL;
 	u64 bytes_search = bytes + empty_size;
 	u64 ret = 0;
@@ -2836,6 +2838,10 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 	ret = offset;
 	if (entry->bitmap) {
 		bitmap_clear_bits(ctl, entry, offset, bytes);
+
+		if (!btrfs_free_space_trimmed(entry))
+			atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
 		if (!entry->bytes)
 			free_bitmap(ctl, entry);
 	} else {
@@ -2844,6 +2850,9 @@ u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 		align_gap = entry->offset;
 		align_gap_trim_state = entry->trim_state;
 
+		if (!btrfs_free_space_trimmed(entry))
+			atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
 		entry->offset = offset + bytes;
 		WARN_ON(entry->bytes < bytes + align_gap_len);
 
@@ -2948,6 +2957,8 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group *block_group,
 			     u64 min_start, u64 *max_extent_size)
 {
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
 	struct btrfs_free_space *entry = NULL;
 	struct rb_node *node;
 	u64 ret = 0;
@@ -3012,6 +3023,9 @@ u64 btrfs_alloc_from_cluster(struct btrfs_block_group *block_group,
 
 	spin_lock(&ctl->tree_lock);
 
+	if (!btrfs_free_space_trimmed(entry))
+		atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
 	ctl->free_space -= bytes;
 	if (!entry->bitmap && !btrfs_free_space_trimmed(entry))
 		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bytes;
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 65417a66866d..a962984004ba 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -456,12 +456,48 @@ static ssize_t btrfs_discardable_bytes_show(struct kobject *kobj,
 }
 BTRFS_ATTR(discard, discardable_bytes, btrfs_discardable_bytes_show);
 
+static ssize_t btrfs_discard_extent_bytes_show(struct kobject *kobj,
+					       struct kobj_attribute *a,
+					       char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+			READ_ONCE(fs_info->discard_ctl.discard_extent_bytes));
+}
+BTRFS_ATTR(discard, discard_extent_bytes, btrfs_discard_extent_bytes_show);
+
+static ssize_t btrfs_discard_bitmap_bytes_show(struct kobject *kobj,
+					       struct kobj_attribute *a,
+					       char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+			READ_ONCE(fs_info->discard_ctl.discard_bitmap_bytes));
+}
+BTRFS_ATTR(discard, discard_bitmap_bytes, btrfs_discard_bitmap_bytes_show);
+
+static ssize_t btrfs_discard_bytes_saved_show(struct kobject *kobj,
+					      struct kobj_attribute *a,
+					      char *buf)
+{
+	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
+
+	return snprintf(buf, PAGE_SIZE, "%lld\n",
+		atomic64_read(&fs_info->discard_ctl.discard_bytes_saved));
+}
+BTRFS_ATTR(discard, discard_bytes_saved, btrfs_discard_bytes_saved_show);
+
 static const struct attribute *discard_debug_attrs[] = {
 	BTRFS_ATTR_PTR(discard, iops_limit),
 	BTRFS_ATTR_PTR(discard, bps_limit),
 	BTRFS_ATTR_PTR(discard, max_discard_size),
 	BTRFS_ATTR_PTR(discard, discardable_extents),
 	BTRFS_ATTR_PTR(discard, discardable_bytes),
+	BTRFS_ATTR_PTR(discard, discard_extent_bytes),
+	BTRFS_ATTR_PTR(discard, discard_bitmap_bytes),
+	BTRFS_ATTR_PTR(discard, discard_bytes_saved),
 	NULL,
 };
 
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 20/22] btrfs: add async discard header
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (18 preceding siblings ...)
  2019-11-25 19:46 ` [PATCH 19/22] btrfs: keep track of discard reuse stats Dennis Zhou
@ 2019-11-25 19:47 ` Dennis Zhou
  2019-11-25 19:47 ` [PATCH 21/22] btrfs: increase the metadata allowance for the free_space_cache Dennis Zhou
                   ` (2 subsequent siblings)
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:47 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Give a brief overview for how async discard is implemented.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/discard.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 7ab4a93fc3b7..66b7855449df 100644
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -1,4 +1,39 @@
 // SPDX-License-Identifier: GPL-2.0
+/*
+ * This contains the logic to handle async discard.
+ *
+ * Async discard manages trimming of free space outside of transaction commit.
+ * Discarding is done by managing the block_groups on a LRU list based on free
+ * space recency.  Two passes are used to first prioritize discarding extents
+ * and then allow for trimming in the bitmap the best opportunity to coalesce.
+ * The block_groups are maintained on multiple lists to allow for multiple
+ * passes with different discard filter requirements.  A delayed work item is
+ * used to manage discarding with timeout determined by a max of the delay
+ * incurred by the iops rate limit, byte rate limit, and the timeout of max
+ * delay of BTRFS_DISCARD_MAX_DELAY.
+ *
+ * The first list is special to manage discarding of fully free block groups.
+ * This is necessary because we issue a final trim for a full free block group
+ * after forgetting it.  When a block group becomes unused, instead of directly
+ * being added to the unused_bgs list, we add it to this first list.  Then
+ * from there, if it becomes fully discarded, we place it onto the unused_bgs
+ * list.
+ *
+ * The in-memory free space cache serves as the backing state for discard.
+ * Consequently this means there is no persistence.  We opt to load all the
+ * block groups in as not discarded, so the mount case degenerates to the
+ * crashing case.
+ *
+ * As the free space cache uses bitmaps, there exists a tradeoff between
+ * ease/efficiency for find_free_extent() and the accuracy of discard state.
+ * Here we opt to let untrimmed regions merge with everything while only letting
+ * trimmed regions merge with other trimmed regions.  This can cause
+ * overtrimming, but the coalescing benefit seems to be worth it.  Additionally,
+ * bitmap state is tracked as a whole.  If we're able to fully trim a bitmap,
+ * the trimmed flag is set on the bitmap.  Otherwise, if an allocation comes in,
+ * this resets the state and we will retry trimming the whole bitmap.  This is a
+ * tradeoff between discard state accuracy and the cost of accounting.
+ */
 
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 21/22] btrfs: increase the metadata allowance for the free_space_cache
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (19 preceding siblings ...)
  2019-11-25 19:47 ` [PATCH 20/22] btrfs: add async discard header Dennis Zhou
@ 2019-11-25 19:47 ` Dennis Zhou
  2019-11-25 19:47 ` [PATCH 22/22] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
  2019-11-26 21:52 ` [PATCH v4 00/22] btrfs: async discard support David Sterba
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:47 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

Currently, there is no way for the free space cache to recover from
being serviced by purely bitmaps because the extent threshold is set to
0 in recalculate_thresholds() when we surpass the metadata allowance.

This adds a recovery mechanism by keeping large extents out of the
bitmaps and increases the metadata upper bound to 64KB. The recovery
mechanism bypasses this upper bound, thus making it a soft upper bound.
But, with the bypass being 1MB or greater, it shouldn't add unbounded
overhead.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/free-space-cache.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 1b887c0d7508..15667095c50d 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -24,7 +24,8 @@
 #include "discard.h"
 
 #define BITS_PER_BITMAP		(PAGE_SIZE * 8UL)
-#define MAX_CACHE_BYTES_PER_GIG	SZ_32K
+#define MAX_CACHE_BYTES_PER_GIG	SZ_64K
+#define FORCE_EXTENT_THRESHOLD	SZ_1M
 
 struct btrfs_trim_range {
 	u64 start;
@@ -1695,26 +1696,17 @@ static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
 	ASSERT(ctl->total_bitmaps <= max_bitmaps);
 
 	/*
-	 * The goal is to keep the total amount of memory used per 1gb of space
-	 * at or below 32k, so we need to adjust how much memory we allow to be
-	 * used by extent based free space tracking
+	 * We are trying to keep the total amount of memory used per 1gb of
+	 * space to be MAX_CACHE_BYTES_PER_GIG.  However, with a reclamation
+	 * mechanism of pulling extents >= FORCE_EXTENT_THRESHOLD out of
+	 * bitmaps, we may end up using more memory than this.
 	 */
 	if (size < SZ_1G)
 		max_bytes = MAX_CACHE_BYTES_PER_GIG;
 	else
 		max_bytes = MAX_CACHE_BYTES_PER_GIG * div_u64(size, SZ_1G);
 
-	/*
-	 * we want to account for 1 more bitmap than what we have so we can make
-	 * sure we don't go over our overall goal of MAX_CACHE_BYTES_PER_GIG as
-	 * we add more bitmaps.
-	 */
-	bitmap_bytes = (ctl->total_bitmaps + 1) * ctl->unit;
-
-	if (bitmap_bytes >= max_bytes) {
-		ctl->extents_thresh = 0;
-		return;
-	}
+	bitmap_bytes = ctl->total_bitmaps * ctl->unit;
 
 	/*
 	 * we want the extent entry threshold to always be at most 1/2 the max
@@ -2100,6 +2092,10 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 		forced = true;
 #endif
 
+	/* This is a way to reclaim large regions from the bitmaps. */
+	if (!forced && info->bytes >= FORCE_EXTENT_THRESHOLD)
+		return false;
+
 	/*
 	 * If we are below the extents threshold then we can add this as an
 	 * extent, and don't have to deal with the bitmap
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* [PATCH 22/22] btrfs: make smaller extents more likely to go into bitmaps
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (20 preceding siblings ...)
  2019-11-25 19:47 ` [PATCH 21/22] btrfs: increase the metadata allowance for the free_space_cache Dennis Zhou
@ 2019-11-25 19:47 ` Dennis Zhou
  2019-11-26 21:52 ` [PATCH v4 00/22] btrfs: async discard support David Sterba
  22 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-25 19:47 UTC (permalink / raw)
  To: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval
  Cc: kernel-team, linux-btrfs, Dennis Zhou

It's less than ideal for small extents to eat into our extent budget, so
force extents <= 32KB into the bitmaps save for the first handful.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/free-space-cache.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 15667095c50d..9167be1e27bf 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2108,8 +2108,8 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 		 * of cache left then go ahead an dadd them, no sense in adding
 		 * the overhead of a bitmap if we don't have to.
 		 */
-		if (info->bytes <= fs_info->sectorsize * 4) {
-			if (ctl->free_extents * 2 <= ctl->extents_thresh)
+		if (info->bytes <= fs_info->sectorsize * 8) {
+			if (ctl->free_extents * 3 <= ctl->extents_thresh)
 				return false;
 		} else {
 			return false;
-- 
2.17.1


^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v4 00/22] btrfs: async discard support
  2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
                   ` (21 preceding siblings ...)
  2019-11-25 19:47 ` [PATCH 22/22] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
@ 2019-11-26 21:52 ` David Sterba
  2019-11-27 18:26   ` Dennis Zhou
  22 siblings, 1 reply; 25+ messages in thread
From: David Sterba @ 2019-11-26 21:52 UTC (permalink / raw)
  To: Dennis Zhou
  Cc: David Sterba, Chris Mason, Josef Bacik, Omar Sandoval,
	kernel-team, linux-btrfs

On Mon, Nov 25, 2019 at 02:46:40PM -0500, Dennis Zhou wrote:
> Hello,
> 
> v3 [1] had 2 minor issues which are fixed:
>  - I was generically dividing u64 which made 32 bit arches unhappy. [2]
>  - Uninitialized use of trim_state local variable [3]

I've started fstests (misc-5.5 + v4) with some debugging options
compiled in and MOUNT_OPTIONS -o discard=async:

btrfs/003:

[   57.263321] BTRFS info (device vdb): relocating block group 30408704 flags metadata|dup
[   57.321441] BTRFS info (device vdb): found 8 extents
[   57.352217] list_add corruption. prev->next should be next (ffff89b6b157f1e0), but was 6b6b6b6b6b6b6b6b. (prev=ffff89b6b3cc59f0).
[   57.355426] ------------[ cut here ]------------
[   57.356895] kernel BUG at lib/list_debug.c:26!
[   57.358303] invalid opcode: 0000 [#1] SMP
[   57.359522] CPU: 1 PID: 19415 Comm: btrfs Not tainted 5.4.0-rc8-default+ #878
[   57.361334] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-rebuilt.opensuse.org 04/01/2014
[   57.364468] RIP: 0010:__list_add_valid+0x5e/0x70
[   57.369959] RSP: 0018:ffff90cbc4c7f8d0 EFLAGS: 00010246
[   57.371475] RAX: 0000000000000075 RBX: ffff89b6b3d04000 RCX: 0000000000000006
[   57.372930] RDX: 0000000000000000 RSI: ffff89b6b2314030 RDI: ffff89b6b2313740
[   57.374893] RBP: ffff89b6b157f0d0 R08: 0000000d5aa62d0d R09: 0000000000000000
[   57.376970] R10: 0000000000000000 R11: 0000000000000000 R12: ffff89b6b3d041f0
[   57.378961] R13: ffff89b6b3cc59f0 R14: ffff89b6b157f190 R15: ffff89b6b157f1e0
[   57.381012] FS:  00007f551b41d8c0(0000) GS:ffff89b6bd800000(0000) knlGS:0000000000000000
[   57.383531] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   57.385264] CR2: 0000563d526212d8 CR3: 0000000073dd3004 CR4: 0000000000160ee0
[   57.387223] Call Trace:
[   57.388250]  btrfs_add_to_discard_unused_list+0xa2/0xe0 [btrfs]
[   57.389804]  btrfs_discard_queue_work+0x3a/0x60 [btrfs]
[   57.390961]  __btrfs_add_free_space+0xe2/0x400 [btrfs]
[   57.401053]  ? do_raw_spin_unlock+0x4b/0xc0
[   57.402419]  ? _raw_spin_unlock+0x24/0x30
[   57.403791]  ? find_first_extent_bit+0xdc/0x120 [btrfs]
[   57.405312]  add_new_free_space+0xd1/0xf0 [btrfs]
[   57.406723]  btrfs_make_block_group+0x9f/0x2e0 [btrfs]
[   57.408222]  __btrfs_alloc_chunk+0x705/0xf00 [btrfs]
[   57.409786]  btrfs_chunk_alloc+0x1a9/0x3f0 [btrfs]
[   57.411354]  btrfs_inc_block_group_ro+0x16d/0x190 [btrfs]
[   57.412897]  btrfs_relocate_block_group+0x60/0x300 [btrfs]
[   57.414430]  btrfs_relocate_chunk+0x32/0xd0 [btrfs]
[   57.415747]  __btrfs_balance+0x41c/0xcc0 [btrfs]
[   57.417084]  btrfs_balance+0x56e/0xa40 [btrfs]
[   57.418361]  ? kmem_cache_alloc_trace+0x281/0x2c0
[   57.419448]  btrfs_ioctl_balance+0x298/0x350 [btrfs]
[   57.420568]  ? mem_cgroup_throttle_swaprate+0xcb/0x2a8
[   57.422306]  btrfs_ioctl+0x466/0x2570 [btrfs]
[   57.423648]  ? __handle_mm_fault+0x499/0x740
[   57.425008]  ? kvm_sched_clock_read+0x14/0x30
[   57.426311]  ? sched_clock+0x5/0x10
[   57.427480]  ? sched_clock_cpu+0x10/0x120
[   57.428856]  ? __handle_mm_fault+0x499/0x740
[   57.430314]  ? do_raw_spin_unlock+0x4b/0xc0
[   57.431695]  ? _raw_spin_unlock+0x24/0x30
[   57.432997]  ? __handle_mm_fault+0x499/0x740
[   57.434370]  ? do_vfs_ioctl+0x405/0x730
[   57.435920]  do_vfs_ioctl+0x405/0x730
[   57.437439]  ? do_user_addr_fault+0x1f1/0x3c0
[   57.439096]  ksys_ioctl+0x3a/0x70
[   57.440518]  ? trace_hardirqs_off_thunk+0x1a/0x20
[   57.442159]  __x64_sys_ioctl+0x16/0x20
[   57.443315]  do_syscall_64+0x50/0x1f0
[   57.444252]  entry_SYSCALL_64_after_hwframe+0x49/0xbek

^ permalink raw reply	[flat|nested] 25+ messages in thread

* Re: [PATCH v4 00/22] btrfs: async discard support
  2019-11-26 21:52 ` [PATCH v4 00/22] btrfs: async discard support David Sterba
@ 2019-11-27 18:26   ` Dennis Zhou
  0 siblings, 0 replies; 25+ messages in thread
From: Dennis Zhou @ 2019-11-27 18:26 UTC (permalink / raw)
  To: David Sterba
  Cc: Dennis Zhou, David Sterba, Chris Mason, Josef Bacik,
	Omar Sandoval, kernel-team, linux-btrfs

On Tue, Nov 26, 2019 at 10:52:04PM +0100, David Sterba wrote:
> On Mon, Nov 25, 2019 at 02:46:40PM -0500, Dennis Zhou wrote:
> > Hello,
> > 
> > v3 [1] had 2 minor issues which are fixed:
> >  - I was generically dividing u64 which made 32 bit arches unhappy. [2]
> >  - Uninitialized use of trim_state local variable [3]
> 
> I've started fstests (misc-5.5 + v4) with some debugging options
> compiled in and MOUNT_OPTIONS -o discard=async:
> 
> btrfs/003:
> 
> [   57.263321] BTRFS info (device vdb): relocating block group 30408704 flags metadata|dup
> [   57.321441] BTRFS info (device vdb): found 8 extents
> [   57.352217] list_add corruption. prev->next should be next (ffff89b6b157f1e0), but was 6b6b6b6b6b6b6b6b. (prev=ffff89b6b3cc59f0).
> [   57.355426] ------------[ cut here ]------------
> [   57.356895] kernel BUG at lib/list_debug.c:26!
> [   57.358303] invalid opcode: 0000 [#1] SMP
> [   57.359522] CPU: 1 PID: 19415 Comm: btrfs Not tainted 5.4.0-rc8-default+ #878
> [   57.361334] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-rebuilt.opensuse.org 04/01/2014
> [   57.364468] RIP: 0010:__list_add_valid+0x5e/0x70
> [   57.369959] RSP: 0018:ffff90cbc4c7f8d0 EFLAGS: 00010246
> [   57.371475] RAX: 0000000000000075 RBX: ffff89b6b3d04000 RCX: 0000000000000006
> [   57.372930] RDX: 0000000000000000 RSI: ffff89b6b2314030 RDI: ffff89b6b2313740
> [   57.374893] RBP: ffff89b6b157f0d0 R08: 0000000d5aa62d0d R09: 0000000000000000
> [   57.376970] R10: 0000000000000000 R11: 0000000000000000 R12: ffff89b6b3d041f0
> [   57.378961] R13: ffff89b6b3cc59f0 R14: ffff89b6b157f190 R15: ffff89b6b157f1e0
> [   57.381012] FS:  00007f551b41d8c0(0000) GS:ffff89b6bd800000(0000) knlGS:0000000000000000
> [   57.383531] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   57.385264] CR2: 0000563d526212d8 CR3: 0000000073dd3004 CR4: 0000000000160ee0
> [   57.387223] Call Trace:
> [   57.388250]  btrfs_add_to_discard_unused_list+0xa2/0xe0 [btrfs]
> [   57.389804]  btrfs_discard_queue_work+0x3a/0x60 [btrfs]
> [   57.390961]  __btrfs_add_free_space+0xe2/0x400 [btrfs]
> [   57.401053]  ? do_raw_spin_unlock+0x4b/0xc0
> [   57.402419]  ? _raw_spin_unlock+0x24/0x30
> [   57.403791]  ? find_first_extent_bit+0xdc/0x120 [btrfs]
> [   57.405312]  add_new_free_space+0xd1/0xf0 [btrfs]
> [   57.406723]  btrfs_make_block_group+0x9f/0x2e0 [btrfs]
> [   57.408222]  __btrfs_alloc_chunk+0x705/0xf00 [btrfs]
> [   57.409786]  btrfs_chunk_alloc+0x1a9/0x3f0 [btrfs]
> [   57.411354]  btrfs_inc_block_group_ro+0x16d/0x190 [btrfs]
> [   57.412897]  btrfs_relocate_block_group+0x60/0x300 [btrfs]
> [   57.414430]  btrfs_relocate_chunk+0x32/0xd0 [btrfs]
> [   57.415747]  __btrfs_balance+0x41c/0xcc0 [btrfs]
> [   57.417084]  btrfs_balance+0x56e/0xa40 [btrfs]
> [   57.418361]  ? kmem_cache_alloc_trace+0x281/0x2c0
> [   57.419448]  btrfs_ioctl_balance+0x298/0x350 [btrfs]
> [   57.420568]  ? mem_cgroup_throttle_swaprate+0xcb/0x2a8
> [   57.422306]  btrfs_ioctl+0x466/0x2570 [btrfs]
> [   57.423648]  ? __handle_mm_fault+0x499/0x740
> [   57.425008]  ? kvm_sched_clock_read+0x14/0x30
> [   57.426311]  ? sched_clock+0x5/0x10
> [   57.427480]  ? sched_clock_cpu+0x10/0x120
> [   57.428856]  ? __handle_mm_fault+0x499/0x740
> [   57.430314]  ? do_raw_spin_unlock+0x4b/0xc0
> [   57.431695]  ? _raw_spin_unlock+0x24/0x30
> [   57.432997]  ? __handle_mm_fault+0x499/0x740
> [   57.434370]  ? do_vfs_ioctl+0x405/0x730
> [   57.435920]  do_vfs_ioctl+0x405/0x730
> [   57.437439]  ? do_user_addr_fault+0x1f1/0x3c0
> [   57.439096]  ksys_ioctl+0x3a/0x70
> [   57.440518]  ? trace_hardirqs_off_thunk+0x1a/0x20
> [   57.442159]  __x64_sys_ioctl+0x16/0x20
> [   57.443315]  do_syscall_64+0x50/0x1f0
> [   57.444252]  entry_SYSCALL_64_after_hwframe+0x49/0xbek

Sigh, I'm sorry about these issues with the series. I think this is
being racy in btrfs_delete_unused_bgs(). I'm working on setting up the
reproducer and fixing it.

Thanks,
Dennis

^ permalink raw reply	[flat|nested] 25+ messages in thread

end of thread, back to index

Thread overview: 25+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-25 19:46 [PATCH v4 00/22] btrfs: async discard support Dennis Zhou
2019-11-25 19:46 ` [PATCH 01/22] bitmap: genericize percpu bitmap region iterators Dennis Zhou
2019-11-25 19:46 ` [PATCH 02/22] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
2019-11-25 19:46 ` [PATCH 03/22] btrfs: keep track of which extents have been discarded Dennis Zhou
2019-11-25 19:46 ` [PATCH 04/22] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
2019-11-25 19:46 ` [PATCH 05/22] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
2019-11-25 19:46 ` [PATCH 06/22] btrfs: handle empty block_group removal Dennis Zhou
2019-11-25 19:46 ` [PATCH 07/22] btrfs: discard one region at a time in async discard Dennis Zhou
2019-11-25 19:46 ` [PATCH 08/22] btrfs: add removal calls for sysfs debug/ Dennis Zhou
2019-11-25 19:46 ` [PATCH 09/22] btrfs: make UUID/debug have its own kobject Dennis Zhou
2019-11-25 19:46 ` [PATCH 10/22] btrfs: add discard sysfs directory Dennis Zhou
2019-11-25 19:46 ` [PATCH 11/22] btrfs: track discardable extents for async discard Dennis Zhou
2019-11-25 19:46 ` [PATCH 12/22] btrfs: keep track of discardable_bytes Dennis Zhou
2019-11-25 19:46 ` [PATCH 13/22] btrfs: calculate discard delay based on number of extents Dennis Zhou
2019-11-25 19:46 ` [PATCH 14/22] btrfs: add bps discard rate limit Dennis Zhou
2019-11-25 19:46 ` [PATCH 15/22] btrfs: limit max discard size for async discard Dennis Zhou
2019-11-25 19:46 ` [PATCH 16/22] btrfs: make max async discard size tunable Dennis Zhou
2019-11-25 19:46 ` [PATCH 17/22] btrfs: have multiple discard lists Dennis Zhou
2019-11-25 19:46 ` [PATCH 18/22] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-11-25 19:46 ` [PATCH 19/22] btrfs: keep track of discard reuse stats Dennis Zhou
2019-11-25 19:47 ` [PATCH 20/22] btrfs: add async discard header Dennis Zhou
2019-11-25 19:47 ` [PATCH 21/22] btrfs: increase the metadata allowance for the free_space_cache Dennis Zhou
2019-11-25 19:47 ` [PATCH 22/22] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
2019-11-26 21:52 ` [PATCH v4 00/22] btrfs: async discard support David Sterba
2019-11-27 18:26   ` Dennis Zhou

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