[RFC PATCH v3.1 0/6] Qgroup fixes, Non-stack version

[RFC PATCH v3.1 0/6] Qgroup fixes, Non-stack version

[Qu Wenruo]

The remaining qgroup fixes patches, based on the Chris' for-linus-4.12
branch with commit 9bcaaea7418d09691f1ffab5c49aacafe3eef9d0 as base.

Can be fetched from github:
https://github.com/adam900710/linux/tree/qgroup_fixes_non_stack

Despite the 5th patch, patches are mostly unchanged.
Only minor conflicts are addressed in this update.

The 5th patch chooses a different method to reduce stack memory usage.

Instead of allocating extent_changeset structure on stack, this time only a
pointer of extent_changeset is allocated on stack.

And real extent_changeset is allocated inside btrfs_qgroup_reserve_data().
The impact to stack memory usage of quota disabled case is reduced to minimal.

While the error handler routine is not affected either.

v2:
  Add reviewed-by tag for 2nd patch
  Update the first patch to follow the new trace point standard
RFC v3:
  Use non-stack (dyanamic allocation) for extent_changeset structure, in
  5th patch, to reduce impact for quota disabled cases.
  Rebase to latest for-linus-4.12 branch.
RFC v3.1:
  Update comment to include the newly introduced parameter
  Use init/release function to replace open coded ulist_init/release().


Qu Wenruo (6):
  btrfs: qgroup: Add quick exit for non-fs extents
  btrfs: qgroup: Cleanup btrfs_qgroup_prepare_account_extents function
  btrfs: qgroup: Return actually freed bytes for qgroup release or free
    data
  btrfs: qgroup: Fix qgroup reserved space underflow caused by buffered
    write and quota enable
  btrfs: qgroup: Introduce extent changeset for qgroup reserve functions
  btrfs: qgroup: Fix qgroup reserved space underflow by only freeing
    reserved ranges

 fs/btrfs/ctree.h       |  12 ++-
 fs/btrfs/extent-tree.c |  37 +++++----
 fs/btrfs/extent_io.h   |  36 ++++++++-
 fs/btrfs/file.c        |  41 ++++++----
 fs/btrfs/inode-map.c   |   4 +-
 fs/btrfs/inode.c       |  58 ++++++++-----
 fs/btrfs/ioctl.c       |   9 ++-
 fs/btrfs/qgroup.c      | 215 ++++++++++++++++++++++++++++++++++++-------------
 fs/btrfs/qgroup.h      |   8 +-
 fs/btrfs/relocation.c  |  12 +--
 fs/btrfs/transaction.c |  10 ---
 11 files changed, 303 insertions(+), 139 deletions(-)
-- 
2.12.2

[RFC PATCH v3.1 1/6] btrfs: qgroup: Add quick exit for non-fs extents

[Qu Wenruo]

For btrfs_qgroup_account_extent(), modify make it exit quicker for
non-fs extents.

This will also reduce the noise in trace_btrfs_qgroup_account_extent
event.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/qgroup.c | 41 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 3f75b5cbbfef..905fed1ee0dd 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1915,6 +1915,33 @@ static int qgroup_update_counters(struct btrfs_fs_info *fs_info,
 	return 0;
 }
 
+/*
+ * Helper to check if the @roots is a list of fs tree roots
+ * Return 0 for definitely not a fs/subvol tree roots ulist
+ * Return 1 for possible fs/subvol tree roots ulist(including empty)
+ */
+static int maybe_fs_roots(struct ulist *roots)
+{
+	struct ulist_node *unode;
+	struct ulist_iterator uiter;
+
+	/* Empty one, still possible for fs roots */
+	if (!roots || roots->nnodes == 0)
+		return 1;
+
+	ULIST_ITER_INIT(&uiter);
+	unode = ulist_next(roots, &uiter);
+	if (!unode)
+		return 1;
+
+	/*
+	 * If it contains fs tree roots, then it must belongs to fs/subvol
+	 * trees.
+	 * If it contains non-fs tree, it won't be shared to fs/subvol trees.
+	 */
+	return is_fstree(unode->val);
+}
+
 int
 btrfs_qgroup_account_extent(struct btrfs_trans_handle *trans,
 			    struct btrfs_fs_info *fs_info,
@@ -1931,10 +1958,20 @@ btrfs_qgroup_account_extent(struct btrfs_trans_handle *trans,
 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
 		return 0;
 
-	if (new_roots)
+	if (new_roots) {
+		if (!maybe_fs_roots(new_roots))
+			goto out_free;
 		nr_new_roots = new_roots->nnodes;
-	if (old_roots)
+	}
+	if (old_roots) {
+		if (!maybe_fs_roots(old_roots))
+			goto out_free;
 		nr_old_roots = old_roots->nnodes;
+	}
+
+	/* Quick exit, either not fs tree roots, or won't affect any qgroup */
+	if (nr_old_roots == 0 && nr_new_roots == 0)
+		goto out_free;
 
 	BUG_ON(!fs_info->quota_root);
 
-- 
2.12.2

[RFC PATCH v3.1 2/6] btrfs: qgroup: Cleanup btrfs_qgroup_prepare_account_extents function

[Qu Wenruo]

Quite a lot of qgroup corruption happens due to wrong timing of calling
btrfs_qgroup_prepare_account_extents().

Since the safest timing is calling it just before
btrfs_qgroup_account_extents(), there is no need to separate these 2
function.

Merging them will make code cleaner and less bug prone.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/qgroup.c      | 50 +++++++++++++++++---------------------------------
 fs/btrfs/qgroup.h      |  2 --
 fs/btrfs/transaction.c | 10 ----------
 3 files changed, 17 insertions(+), 45 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 905fed1ee0dd..9f01c25469f7 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1403,38 +1403,6 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-int btrfs_qgroup_prepare_account_extents(struct btrfs_trans_handle *trans,
-					 struct btrfs_fs_info *fs_info)
-{
-	struct btrfs_qgroup_extent_record *record;
-	struct btrfs_delayed_ref_root *delayed_refs;
-	struct rb_node *node;
-	u64 qgroup_to_skip;
-	int ret = 0;
-
-	delayed_refs = &trans->transaction->delayed_refs;
-	qgroup_to_skip = delayed_refs->qgroup_to_skip;
-
-	/*
-	 * No need to do lock, since this function will only be called in
-	 * btrfs_commit_transaction().
-	 */
-	node = rb_first(&delayed_refs->dirty_extent_root);
-	while (node) {
-		record = rb_entry(node, struct btrfs_qgroup_extent_record,
-				  node);
-		if (WARN_ON(!record->old_roots))
-			ret = btrfs_find_all_roots(NULL, fs_info,
-					record->bytenr, 0, &record->old_roots);
-		if (ret < 0)
-			break;
-		if (qgroup_to_skip)
-			ulist_del(record->old_roots, qgroup_to_skip, 0);
-		node = rb_next(node);
-	}
-	return ret;
-}
-
 int btrfs_qgroup_trace_extent_nolock(struct btrfs_fs_info *fs_info,
 				struct btrfs_delayed_ref_root *delayed_refs,
 				struct btrfs_qgroup_extent_record *record)
@@ -2051,6 +2019,19 @@ int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans,
 
 		if (!ret) {
 			/*
+			 * old roots should be searched when inserting qgroup
+			 * extent record
+			 */
+			if (WARN_ON(!record->old_roots)) {
+				/* Search commit root to find old_roots */
+				ret = btrfs_find_all_roots(NULL, fs_info,
+						record->bytenr, 0,
+						&record->old_roots);
+				if (ret < 0)
+					goto cleanup;
+			}
+
+			/*
 			 * Use SEQ_LAST as time_seq to do special search, which
 			 * doesn't lock tree or delayed_refs and search current
 			 * root. It's safe inside commit_transaction().
@@ -2059,8 +2040,11 @@ int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans,
 					record->bytenr, SEQ_LAST, &new_roots);
 			if (ret < 0)
 				goto cleanup;
-			if (qgroup_to_skip)
+			if (qgroup_to_skip) {
 				ulist_del(new_roots, qgroup_to_skip, 0);
+				ulist_del(record->old_roots, qgroup_to_skip,
+					  0);
+			}
 			ret = btrfs_qgroup_account_extent(trans, fs_info,
 					record->bytenr, record->num_bytes,
 					record->old_roots, new_roots);
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index fe04d3f295c6..38d14d4575c0 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -134,8 +134,6 @@ int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
 int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info);
 void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info);
 struct btrfs_delayed_extent_op;
-int btrfs_qgroup_prepare_account_extents(struct btrfs_trans_handle *trans,
-					 struct btrfs_fs_info *fs_info);
 /*
  * Inform qgroup to trace one dirty extent, its info is recorded in @record.
  * So qgroup can account it at transaction committing time.
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 2168654c90a1..ee5b41d297d1 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1374,9 +1374,6 @@ static int qgroup_account_snapshot(struct btrfs_trans_handle *trans,
 	ret = commit_fs_roots(trans, fs_info);
 	if (ret)
 		goto out;
-	ret = btrfs_qgroup_prepare_account_extents(trans, fs_info);
-	if (ret < 0)
-		goto out;
 	ret = btrfs_qgroup_account_extents(trans, fs_info);
 	if (ret < 0)
 		goto out;
@@ -2180,13 +2177,6 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 		goto scrub_continue;
 	}
 
-	ret = btrfs_qgroup_prepare_account_extents(trans, fs_info);
-	if (ret) {
-		mutex_unlock(&fs_info->tree_log_mutex);
-		mutex_unlock(&fs_info->reloc_mutex);
-		goto scrub_continue;
-	}
-
 	/*
 	 * Since fs roots are all committed, we can get a quite accurate
 	 * new_roots. So let's do quota accounting.
-- 
2.12.2

[RFC PATCH v3.1 3/6] btrfs: qgroup: Return actually freed bytes for qgroup release or free data

[Qu Wenruo]

btrfs_qgroup_release/free_data() only returns 0 or minus error
number(ENOMEM is the only possible error).

This is normally good enough, but sometimes we need the accurate byte
number it freed/released.

Change it to return actually released/freed bytenr number instead of 0
for success.
And slightly modify related extent_changeset structure, since in btrfs
one none-hole data extent won't be larger than 128M, so "unsigned int"
is large enough for the use case.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/extent-tree.c | 2 +-
 fs/btrfs/extent_io.h   | 2 +-
 fs/btrfs/qgroup.c      | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e390451c72e6..4f62696131a6 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4298,7 +4298,7 @@ int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len)
 
 	/* Use new btrfs_qgroup_reserve_data to reserve precious data space. */
 	ret = btrfs_qgroup_reserve_data(inode, start, len);
-	if (ret)
+	if (ret < 0)
 		btrfs_free_reserved_data_space_noquota(inode, start, len);
 	return ret;
 }
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 1eafa2f0ede3..cc1b08fa9fe7 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -205,7 +205,7 @@ struct extent_buffer {
  */
 struct extent_changeset {
 	/* How many bytes are set/cleared in this operation */
-	u64 bytes_changed;
+	unsigned int bytes_changed;
 
 	/* Changed ranges */
 	struct ulist range_changed;
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 9f01c25469f7..ad2e99491395 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2886,6 +2886,7 @@ static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
 		btrfs_qgroup_free_refroot(BTRFS_I(inode)->root->fs_info,
 				BTRFS_I(inode)->root->objectid,
 				changeset.bytes_changed);
+	ret = changeset.bytes_changed;
 out:
 	ulist_release(&changeset.range_changed);
 	return ret;
-- 
2.12.2

[RFC PATCH v3.1 4/6] btrfs: qgroup: Fix qgroup reserved space underflow caused by buffered write and quota enable

[Qu Wenruo]

[BUG]
Under the following case, we can underflow qgroup reserved space.

            Task A                |            Task B
---------------------------------------------------------------
 Quota disabled                   |
 Buffered write                   |
 |- btrfs_check_data_free_space() |
 |  *NO* qgroup space is reserved |
 |  since quota is *DISABLED*     |
 |- All pages are copied to page  |
    cache                         |
                                  | Enable quota
                                  | Quota scan finished
                                  |
                                  | Sync_fs
                                  | |- run_delalloc_range
                                  | |- Write pages
                                  | |- btrfs_finish_ordered_io
                                  |    |- insert_reserved_file_extent
                                  |       |- btrfs_qgroup_release_data()
                                  |          Since no qgroup space is
                                             reserved in Task A, we
                                             underflow qgroup reserved
                                             space
This can be detected by fstest btrfs/104.

[CAUSE]
In insert_reserved_file_extent() we info qgroup to release the @ram_bytes
size of qgroup reserved_space under all case.
And btrfs_qgroup_release_data() will check if qgroup is enabled.

However in above case, the buffered write happens before quota is
enabled, so we don't havee reserved space for that range.

[FIX]
In insert_reserved_file_extent(), we info qgroup to release the acctual
byte number it released.
In above case, since we don't have reserved space, we info qgroup to
release 0 byte, so the problem can be fixed.

And thanks to the @reserved parameter introduced by qgroup rework, and
previous patch to return release bytes, the fix can be as small as less
than 10 lines.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/inode.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 17cbe9306faf..a1294d5baef5 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2143,6 +2143,7 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_key ins;
+	u64 qg_released;
 	int extent_inserted = 0;
 	int ret;
 
@@ -2198,13 +2199,17 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 	ins.objectid = disk_bytenr;
 	ins.offset = disk_num_bytes;
 	ins.type = BTRFS_EXTENT_ITEM_KEY;
-	ret = btrfs_alloc_reserved_file_extent(trans, root->root_key.objectid,
-			btrfs_ino(BTRFS_I(inode)), file_pos, ram_bytes, &ins);
+
 	/*
 	 * Release the reserved range from inode dirty range map, as it is
 	 * already moved into delayed_ref_head
 	 */
-	btrfs_qgroup_release_data(inode, file_pos, ram_bytes);
+	ret = btrfs_qgroup_release_data(inode, file_pos, ram_bytes);
+	if (ret < 0)
+		goto out;
+	qg_released = ret;
+	ret = btrfs_alloc_reserved_file_extent(trans, root->root_key.objectid,
+			btrfs_ino(BTRFS_I(inode)), file_pos, qg_released, &ins);
 out:
 	btrfs_free_path(path);
 
-- 
2.12.2

[RFC PATCH v3.1 5/6] btrfs: qgroup: Introduce extent changeset for qgroup reserve functions

[Qu Wenruo]

Introduce a new parameter, struct extent_changeset for
btrfs_qgroup_reserved_data() and its callers.

Such extent_changeset was used in btrfs_qgroup_reserve_data() to record
which range it reserved in current reserve, so it can free it at error
path.

The reason we need to export it to callers is, at buffered write error
path, without knowing what exactly which range we reserved in current
allocation, we can free space which is not reserved by us.

This will lead to qgroup reserved space underflow.

Reviewed-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/ctree.h       |  6 ++++--
 fs/btrfs/extent-tree.c | 23 +++++++++++++----------
 fs/btrfs/extent_io.h   | 34 +++++++++++++++++++++++++++++++++
 fs/btrfs/file.c        | 12 +++++++++---
 fs/btrfs/inode-map.c   |  4 +++-
 fs/btrfs/inode.c       | 18 ++++++++++++++----
 fs/btrfs/ioctl.c       |  5 ++++-
 fs/btrfs/qgroup.c      | 51 ++++++++++++++++++++++++++++++++------------------
 fs/btrfs/qgroup.h      |  3 ++-
 fs/btrfs/relocation.c  |  4 +++-
 10 files changed, 119 insertions(+), 41 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1e82516fe2d8..52a0147cd612 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2704,8 +2704,9 @@ enum btrfs_flush_state {
 	COMMIT_TRANS		=	6,
 };
 
-int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len);
 int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes);
+int btrfs_check_data_free_space(struct inode *inode,
+			struct extent_changeset **reserved, u64 start, u64 len);
 void btrfs_free_reserved_data_space(struct inode *inode, u64 start, u64 len);
 void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start,
 					    u64 len);
@@ -2723,7 +2724,8 @@ void btrfs_subvolume_release_metadata(struct btrfs_fs_info *fs_info,
 				      struct btrfs_block_rsv *rsv);
 int btrfs_delalloc_reserve_metadata(struct btrfs_inode *inode, u64 num_bytes);
 void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes);
-int btrfs_delalloc_reserve_space(struct inode *inode, u64 start, u64 len);
+int btrfs_delalloc_reserve_space(struct inode *inode,
+			struct extent_changeset **reserved, u64 start, u64 len);
 void btrfs_delalloc_release_space(struct inode *inode, u64 start, u64 len);
 void btrfs_init_block_rsv(struct btrfs_block_rsv *rsv, unsigned short type);
 struct btrfs_block_rsv *btrfs_alloc_block_rsv(struct btrfs_fs_info *fs_info,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4f62696131a6..ef09cc37f25f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3364,6 +3364,7 @@ static int cache_save_setup(struct btrfs_block_group_cache *block_group,
 	struct btrfs_fs_info *fs_info = block_group->fs_info;
 	struct btrfs_root *root = fs_info->tree_root;
 	struct inode *inode = NULL;
+	struct extent_changeset *data_reserved = NULL;
 	u64 alloc_hint = 0;
 	int dcs = BTRFS_DC_ERROR;
 	u64 num_pages = 0;
@@ -3483,7 +3484,7 @@ static int cache_save_setup(struct btrfs_block_group_cache *block_group,
 	num_pages *= 16;
 	num_pages *= PAGE_SIZE;
 
-	ret = btrfs_check_data_free_space(inode, 0, num_pages);
+	ret = btrfs_check_data_free_space(inode, &data_reserved, 0, num_pages);
 	if (ret)
 		goto out_put;
 
@@ -3514,6 +3515,7 @@ static int cache_save_setup(struct btrfs_block_group_cache *block_group,
 	block_group->disk_cache_state = dcs;
 	spin_unlock(&block_group->lock);
 
+	extent_changeset_free(data_reserved);
 	return ret;
 }
 
@@ -4277,12 +4279,8 @@ int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes)
 	return ret;
 }
 
-/*
- * New check_data_free_space() with ability for precious data reservation
- * Will replace old btrfs_check_data_free_space(), but for patch split,
- * add a new function first and then replace it.
- */
-int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len)
+int btrfs_check_data_free_space(struct inode *inode,
+			struct extent_changeset **reserved, u64 start, u64 len)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	int ret;
@@ -4297,9 +4295,11 @@ int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len)
 		return ret;
 
 	/* Use new btrfs_qgroup_reserve_data to reserve precious data space. */
-	ret = btrfs_qgroup_reserve_data(inode, start, len);
+	ret = btrfs_qgroup_reserve_data(inode, reserved, start, len);
 	if (ret < 0)
 		btrfs_free_reserved_data_space_noquota(inode, start, len);
+	else
+		ret = 0;
 	return ret;
 }
 
@@ -6123,6 +6123,8 @@ void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes)
  * @inode: inode we're writing to
  * @start: start range we are writing to
  * @len: how long the range we are writing to
+ * @reserved: mandatory parameter, record actually reserved qgroup ranges of
+ * 	      current reservation.
  *
  * This will do the following things
  *
@@ -6140,11 +6142,12 @@ void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes)
  * Return 0 for success
  * Return <0 for error(-ENOSPC or -EQUOT)
  */
-int btrfs_delalloc_reserve_space(struct inode *inode, u64 start, u64 len)
+int btrfs_delalloc_reserve_space(struct inode *inode,
+			struct extent_changeset **reserved, u64 start, u64 len)
 {
 	int ret;
 
-	ret = btrfs_check_data_free_space(inode, start, len);
+	ret = btrfs_check_data_free_space(inode, reserved, start, len);
 	if (ret < 0)
 		return ret;
 	ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), len);
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index cc1b08fa9fe7..afb3553f4f78 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -211,6 +211,40 @@ struct extent_changeset {
 	struct ulist range_changed;
 };
 
+static inline void extent_changeset_init(struct extent_changeset *changeset)
+{
+	changeset->bytes_changed = 0;
+	ulist_init(&changeset->range_changed);
+}
+
+static inline struct extent_changeset *extent_changeset_alloc(void)
+{
+	struct extent_changeset *ret;
+
+	ret = kmalloc(sizeof(*ret), GFP_KERNEL);
+	if (!ret)
+		return NULL;
+
+	extent_changeset_init(ret);
+	return ret;
+}
+
+static inline void extent_changeset_release(struct extent_changeset *changeset)
+{
+	if (!changeset)
+		return;
+	changeset->bytes_changed = 0;
+	ulist_release(&changeset->range_changed);
+}
+
+static inline void extent_changeset_free(struct extent_changeset *changeset)
+{
+	if (!changeset)
+		return;
+	extent_changeset_release(changeset);
+	kfree(changeset);
+}
+
 static inline void extent_set_compress_type(unsigned long *bio_flags,
 					    int compress_type)
 {
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index da1096eb1a40..d31c935b36ed 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1581,6 +1581,7 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct page **pages = NULL;
 	struct extent_state *cached_state = NULL;
+	struct extent_changeset *data_reserved = NULL;
 	u64 release_bytes = 0;
 	u64 lockstart;
 	u64 lockend;
@@ -1628,7 +1629,9 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 		reserve_bytes = round_up(write_bytes + sector_offset,
 				fs_info->sectorsize);
 
-		ret = btrfs_check_data_free_space(inode, pos, write_bytes);
+		extent_changeset_release(data_reserved);
+		ret = btrfs_check_data_free_space(inode, &data_reserved, pos,
+						  write_bytes);
 		if (ret < 0) {
 			if ((BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
 						      BTRFS_INODE_PREALLOC)) &&
@@ -1802,6 +1805,7 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 		}
 	}
 
+	extent_changeset_free(data_reserved);
 	return num_written ? num_written : ret;
 }
 
@@ -2769,6 +2773,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 {
 	struct inode *inode = file_inode(file);
 	struct extent_state *cached_state = NULL;
+	struct extent_changeset *data_reserved = NULL;
 	struct falloc_range *range;
 	struct falloc_range *tmp;
 	struct list_head reserve_list;
@@ -2898,8 +2903,8 @@ static long btrfs_fallocate(struct file *file, int mode,
 				free_extent_map(em);
 				break;
 			}
-			ret = btrfs_qgroup_reserve_data(inode, cur_offset,
-					last_byte - cur_offset);
+			ret = btrfs_qgroup_reserve_data(inode, &data_reserved,
+					cur_offset, last_byte - cur_offset);
 			if (ret < 0) {
 				free_extent_map(em);
 				break;
@@ -2971,6 +2976,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 	if (ret != 0)
 		btrfs_free_reserved_data_space(inode, alloc_start,
 				       alloc_end - cur_offset);
+	extent_changeset_free(data_reserved);
 	return ret;
 }
 
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 5c6c20ec64d8..d02019747d00 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -400,6 +400,7 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
 	struct btrfs_path *path;
 	struct inode *inode;
 	struct btrfs_block_rsv *rsv;
+	struct extent_changeset *data_reserved = NULL;
 	u64 num_bytes;
 	u64 alloc_hint = 0;
 	int ret;
@@ -492,7 +493,7 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
 	/* Just to make sure we have enough space */
 	prealloc += 8 * PAGE_SIZE;
 
-	ret = btrfs_delalloc_reserve_space(inode, 0, prealloc);
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, 0, prealloc);
 	if (ret)
 		goto out_put;
 
@@ -516,6 +517,7 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
 	trans->bytes_reserved = num_bytes;
 
 	btrfs_free_path(path);
+	extent_changeset_free(data_reserved);
 	return ret;
 }
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a1294d5baef5..4e211b54b267 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2035,6 +2035,7 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
 	struct btrfs_writepage_fixup *fixup;
 	struct btrfs_ordered_extent *ordered;
 	struct extent_state *cached_state = NULL;
+	struct extent_changeset *data_reserved = NULL;
 	struct page *page;
 	struct inode *inode;
 	u64 page_start;
@@ -2072,7 +2073,7 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
 		goto again;
 	}
 
-	ret = btrfs_delalloc_reserve_space(inode, page_start,
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start,
 					   PAGE_SIZE);
 	if (ret) {
 		mapping_set_error(page->mapping, ret);
@@ -2092,6 +2093,7 @@ static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
 	unlock_page(page);
 	put_page(page);
 	kfree(fixup);
+	extent_changeset_free(data_reserved);
 }
 
 /*
@@ -4767,6 +4769,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	struct btrfs_ordered_extent *ordered;
 	struct extent_state *cached_state = NULL;
+	struct extent_changeset *data_reserved = NULL;
 	char *kaddr;
 	u32 blocksize = fs_info->sectorsize;
 	pgoff_t index = from >> PAGE_SHIFT;
@@ -4781,7 +4784,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	    (!len || ((len & (blocksize - 1)) == 0)))
 		goto out;
 
-	ret = btrfs_delalloc_reserve_space(inode,
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved,
 			round_down(from, blocksize), blocksize);
 	if (ret)
 		goto out;
@@ -4866,6 +4869,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 	unlock_page(page);
 	put_page(page);
 out:
+	extent_changeset_free(data_reserved);
 	return ret;
 }
 
@@ -8725,6 +8729,7 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 	struct inode *inode = file->f_mapping->host;
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_dio_data dio_data = { 0 };
+	struct extent_changeset *data_reserved = NULL;
 	loff_t offset = iocb->ki_pos;
 	size_t count = 0;
 	int flags = 0;
@@ -8761,7 +8766,8 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 			inode_unlock(inode);
 			relock = true;
 		}
-		ret = btrfs_delalloc_reserve_space(inode, offset, count);
+		ret = btrfs_delalloc_reserve_space(inode, &data_reserved,
+						   offset, count);
 		if (ret)
 			goto out;
 		dio_data.outstanding_extents = count_max_extents(count);
@@ -8818,6 +8824,7 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 	if (relock)
 		inode_lock(inode);
 
+	extent_changeset_free(data_reserved);
 	return ret;
 }
 
@@ -9050,6 +9057,7 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	struct btrfs_ordered_extent *ordered;
 	struct extent_state *cached_state = NULL;
+	struct extent_changeset *data_reserved = NULL;
 	char *kaddr;
 	unsigned long zero_start;
 	loff_t size;
@@ -9075,7 +9083,7 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	 * end up waiting indefinitely to get a lock on the page currently
 	 * being processed by btrfs_page_mkwrite() function.
 	 */
-	ret = btrfs_delalloc_reserve_space(inode, page_start,
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved, page_start,
 					   reserved_space);
 	if (!ret) {
 		ret = file_update_time(vmf->vma->vm_file);
@@ -9181,6 +9189,7 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 out_unlock:
 	if (!ret) {
 		sb_end_pagefault(inode->i_sb);
+		extent_changeset_free(data_reserved);
 		return VM_FAULT_LOCKED;
 	}
 	unlock_page(page);
@@ -9188,6 +9197,7 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	btrfs_delalloc_release_space(inode, page_start, reserved_space);
 out_noreserve:
 	sb_end_pagefault(inode->i_sb);
+	extent_changeset_free(data_reserved);
 	return ret;
 }
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a29dc3fd7152..a16a16a66ed9 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1127,6 +1127,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 	struct btrfs_ordered_extent *ordered;
 	struct extent_state *cached_state = NULL;
 	struct extent_io_tree *tree;
+	struct extent_changeset *data_reserved = NULL;
 	gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
 
 	file_end = (isize - 1) >> PAGE_SHIFT;
@@ -1135,7 +1136,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 
 	page_cnt = min_t(u64, (u64)num_pages, (u64)file_end - start_index + 1);
 
-	ret = btrfs_delalloc_reserve_space(inode,
+	ret = btrfs_delalloc_reserve_space(inode, &data_reserved,
 			start_index << PAGE_SHIFT,
 			page_cnt << PAGE_SHIFT);
 	if (ret)
@@ -1247,6 +1248,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 		unlock_page(pages[i]);
 		put_page(pages[i]);
 	}
+	extent_changeset_free(data_reserved);
 	return i_done;
 out:
 	for (i = 0; i < i_done; i++) {
@@ -1256,6 +1258,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 	btrfs_delalloc_release_space(inode,
 			start_index << PAGE_SHIFT,
 			page_cnt << PAGE_SHIFT);
+	extent_changeset_free(data_reserved);
 	return ret;
 
 }
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index ad2e99491395..6086a648e67e 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2824,43 +2824,60 @@ btrfs_qgroup_rescan_resume(struct btrfs_fs_info *fs_info)
  * Return <0 for error (including -EQUOT)
  *
  * NOTE: this function may sleep for memory allocation.
+ *       if btrfs_qgroup_reserve_data() is called multiple times with
+ *       same @reserved, caller must ensure when error happens it's OK
+ *       to free *ALL* reserved space.
  */
-int btrfs_qgroup_reserve_data(struct inode *inode, u64 start, u64 len)
+int btrfs_qgroup_reserve_data(struct inode *inode,
+			struct extent_changeset **reserved_ret, u64 start,
+			u64 len)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct extent_changeset changeset;
 	struct ulist_node *unode;
 	struct ulist_iterator uiter;
+	struct extent_changeset *reserved;
+	u64 orig_reserved;
+	u64 to_reserve;
 	int ret;
 
 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &root->fs_info->flags) ||
 	    !is_fstree(root->objectid) || len == 0)
 		return 0;
 
-	changeset.bytes_changed = 0;
-	ulist_init(&changeset.range_changed);
+	/* @reserved parameter is mandatory for qgroup */
+	if (WARN_ON(!reserved_ret))
+		return -EINVAL;
+	if (!*reserved_ret) {
+		*reserved_ret = extent_changeset_alloc();
+		if (!*reserved_ret)
+			return -ENOMEM;
+	}
+	reserved = *reserved_ret;
+	/* Record already reserved space */
+	orig_reserved = reserved->bytes_changed;
 	ret = set_record_extent_bits(&BTRFS_I(inode)->io_tree, start,
-			start + len -1, EXTENT_QGROUP_RESERVED, &changeset);
+			start + len -1, EXTENT_QGROUP_RESERVED, reserved);
+
+	/* Newly reserved space */
+	to_reserve = reserved->bytes_changed - orig_reserved;
 	trace_btrfs_qgroup_reserve_data(inode, start, len,
-					changeset.bytes_changed,
-					QGROUP_RESERVE);
+					to_reserve, QGROUP_RESERVE);
 	if (ret < 0)
 		goto cleanup;
-	ret = qgroup_reserve(root, changeset.bytes_changed, true);
+	ret = qgroup_reserve(root, to_reserve, true);
 	if (ret < 0)
 		goto cleanup;
 
-	ulist_release(&changeset.range_changed);
 	return ret;
 
 cleanup:
-	/* cleanup already reserved ranges */
+	/* cleanup *ALL* already reserved ranges */
 	ULIST_ITER_INIT(&uiter);
-	while ((unode = ulist_next(&changeset.range_changed, &uiter)))
+	while ((unode = ulist_next(&reserved->range_changed, &uiter)))
 		clear_extent_bit(&BTRFS_I(inode)->io_tree, unode->val,
 				 unode->aux, EXTENT_QGROUP_RESERVED, 0, 0, NULL,
 				 GFP_NOFS);
-	ulist_release(&changeset.range_changed);
+	extent_changeset_release(reserved);
 	return ret;
 }
 
@@ -2871,8 +2888,7 @@ static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
 	int trace_op = QGROUP_RELEASE;
 	int ret;
 
-	changeset.bytes_changed = 0;
-	ulist_init(&changeset.range_changed);
+	extent_changeset_init(&changeset);
 	ret = clear_record_extent_bits(&BTRFS_I(inode)->io_tree, start, 
 			start + len -1, EXTENT_QGROUP_RESERVED, &changeset);
 	if (ret < 0)
@@ -2888,7 +2904,7 @@ static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
 				changeset.bytes_changed);
 	ret = changeset.bytes_changed;
 out:
-	ulist_release(&changeset.range_changed);
+	extent_changeset_release(&changeset);
 	return ret;
 }
 
@@ -2988,8 +3004,7 @@ void btrfs_qgroup_check_reserved_leak(struct inode *inode)
 	struct ulist_iterator iter;
 	int ret;
 
-	changeset.bytes_changed = 0;
-	ulist_init(&changeset.range_changed);
+	extent_changeset_init(&changeset);
 	ret = clear_record_extent_bits(&BTRFS_I(inode)->io_tree, 0, (u64)-1,
 			EXTENT_QGROUP_RESERVED, &changeset);
 
@@ -3006,5 +3021,5 @@ void btrfs_qgroup_check_reserved_leak(struct inode *inode)
 				changeset.bytes_changed);
 
 	}
-	ulist_release(&changeset.range_changed);
+	extent_changeset_release(&changeset);
 }
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index 38d14d4575c0..c7a2bcaff5d5 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -241,7 +241,8 @@ int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
 #endif
 
 /* New io_tree based accurate qgroup reserve API */
-int btrfs_qgroup_reserve_data(struct inode *inode, u64 start, u64 len);
+int btrfs_qgroup_reserve_data(struct inode *inode,
+			struct extent_changeset **reserved, u64 start, u64 len);
 int btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len);
 int btrfs_qgroup_free_data(struct inode *inode, u64 start, u64 len);
 
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index d60df51959f7..5823e2d67a84 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3093,11 +3093,12 @@ int prealloc_file_extent_cluster(struct inode *inode,
 	u64 prealloc_start = cluster->start - offset;
 	u64 prealloc_end = cluster->end - offset;
 	u64 cur_offset;
+	struct extent_changeset *data_reserved = NULL;
 
 	BUG_ON(cluster->start != cluster->boundary[0]);
 	inode_lock(inode);
 
-	ret = btrfs_check_data_free_space(inode, prealloc_start,
+	ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
 					  prealloc_end + 1 - prealloc_start);
 	if (ret)
 		goto out;
@@ -3129,6 +3130,7 @@ int prealloc_file_extent_cluster(struct inode *inode,
 				       prealloc_end + 1 - cur_offset);
 out:
 	inode_unlock(inode);
+	extent_changeset_free(data_reserved);
 	return ret;
 }
 
-- 
2.12.2

[RFC PATCH v3.1 6/6] btrfs: qgroup: Fix qgroup reserved space underflow by only freeing reserved ranges

[Qu Wenruo]

[BUG]
For the following case, btrfs can underflow qgroup reserved space
at error path:
(Page size 4K, function name without "btrfs_" prefix)

         Task A                  |             Task B
----------------------------------------------------------------------
Buffered_write [0, 2K)           |
|- check_data_free_space()       |
|  |- qgroup_reserve_data()      |
|     Range aligned to page      |
|     range [0, 4K)          <<< |
|     4K bytes reserved      <<< |
|- copy pages to page cache      |
                                 | Buffered_write [2K, 4K)
                                 | |- check_data_free_space()
                                 | |  |- qgroup_reserved_data()
                                 | |     Range alinged to page
                                 | |     range [0, 4K)
                                 | |     Already reserved by A <<<
                                 | |     0 bytes reserved      <<<
                                 | |- delalloc_reserve_metadata()
                                 | |  And it *FAILED* (Maybe EQUOTA)
                                 | |- free_reserved_data_space()
                                      |- qgroup_free_data()
                                         Range aligned to page range
                                         [0, 4K)
                                         Freeing 4K
(Special thanks to Chandan for the detailed report and analyse)

[CAUSE]
Above Task B is freeing reserved data range [0, 4K) which is actually
reserved by Task A.

And at write back time, page dirty by Task A will go through writeback
routine, which will free 4K reserved data space at file extent insert
time, causing the qgroup underflow.

[FIX]
For btrfs_qgroup_free_data(), add @reserved parameter to only free
data ranges reserved by previous btrfs_qgroup_reserve_data().
So in above case, Task B will try to free 0 byte, so no underflow.

Reported-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Tested-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
---
 fs/btrfs/ctree.h       |  6 +++--
 fs/btrfs/extent-tree.c | 12 +++++----
 fs/btrfs/file.c        | 29 +++++++++++---------
 fs/btrfs/inode.c       | 29 ++++++++++----------
 fs/btrfs/ioctl.c       |  4 +--
 fs/btrfs/qgroup.c      | 72 ++++++++++++++++++++++++++++++++++++++++++++++----
 fs/btrfs/qgroup.h      |  3 ++-
 fs/btrfs/relocation.c  |  8 +++---
 8 files changed, 117 insertions(+), 46 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 52a0147cd612..75d2eced61b2 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2707,7 +2707,10 @@ enum btrfs_flush_state {
 int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes);
 int btrfs_check_data_free_space(struct inode *inode,
 			struct extent_changeset **reserved, u64 start, u64 len);
-void btrfs_free_reserved_data_space(struct inode *inode, u64 start, u64 len);
+void btrfs_free_reserved_data_space(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len);
+void btrfs_delalloc_release_space(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len);
 void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start,
 					    u64 len);
 void btrfs_trans_release_metadata(struct btrfs_trans_handle *trans,
@@ -2726,7 +2729,6 @@ int btrfs_delalloc_reserve_metadata(struct btrfs_inode *inode, u64 num_bytes);
 void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes);
 int btrfs_delalloc_reserve_space(struct inode *inode,
 			struct extent_changeset **reserved, u64 start, u64 len);
-void btrfs_delalloc_release_space(struct inode *inode, u64 start, u64 len);
 void btrfs_init_block_rsv(struct btrfs_block_rsv *rsv, unsigned short type);
 struct btrfs_block_rsv *btrfs_alloc_block_rsv(struct btrfs_fs_info *fs_info,
 					      unsigned short type);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ef09cc37f25f..eeeccc8a618e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4340,7 +4340,8 @@ void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start,
  * This one will handle the per-inode data rsv map for accurate reserved
  * space framework.
  */
-void btrfs_free_reserved_data_space(struct inode *inode, u64 start, u64 len)
+void btrfs_free_reserved_data_space(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 
@@ -4350,7 +4351,7 @@ void btrfs_free_reserved_data_space(struct inode *inode, u64 start, u64 len)
 	start = round_down(start, root->fs_info->sectorsize);
 
 	btrfs_free_reserved_data_space_noquota(inode, start, len);
-	btrfs_qgroup_free_data(inode, start, len);
+	btrfs_qgroup_free_data(inode, reserved, start, len);
 }
 
 static void force_metadata_allocation(struct btrfs_fs_info *info)
@@ -6152,7 +6153,7 @@ int btrfs_delalloc_reserve_space(struct inode *inode,
 		return ret;
 	ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode), len);
 	if (ret < 0)
-		btrfs_free_reserved_data_space(inode, start, len);
+		btrfs_free_reserved_data_space(inode, *reserved, start, len);
 	return ret;
 }
 
@@ -6171,10 +6172,11 @@ int btrfs_delalloc_reserve_space(struct inode *inode,
  * list if there are no delalloc bytes left.
  * Also it will handle the qgroup reserved space.
  */
-void btrfs_delalloc_release_space(struct inode *inode, u64 start, u64 len)
+void btrfs_delalloc_release_space(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len)
 {
 	btrfs_delalloc_release_metadata(BTRFS_I(inode), len);
-	btrfs_free_reserved_data_space(inode, start, len);
+	btrfs_free_reserved_data_space(inode, reserved, start, len);
 }
 
 static int update_block_group(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index d31c935b36ed..0502bd2272fe 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1660,8 +1660,9 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 				reserve_bytes);
 		if (ret) {
 			if (!only_release_metadata)
-				btrfs_free_reserved_data_space(inode, pos,
-							       write_bytes);
+				btrfs_free_reserved_data_space(inode,
+						data_reserved, pos,
+						write_bytes);
 			else
 				btrfs_end_write_no_snapshoting(root);
 			break;
@@ -1743,8 +1744,9 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 				__pos = round_down(pos,
 						   fs_info->sectorsize) +
 					(dirty_pages << PAGE_SHIFT);
-				btrfs_delalloc_release_space(inode, __pos,
-							     release_bytes);
+				btrfs_delalloc_release_space(inode,
+						data_reserved, __pos,
+						release_bytes);
 			}
 		}
 
@@ -1799,9 +1801,9 @@ static noinline ssize_t __btrfs_buffered_write(struct file *file,
 			btrfs_delalloc_release_metadata(BTRFS_I(inode),
 					release_bytes);
 		} else {
-			btrfs_delalloc_release_space(inode,
-						round_down(pos, fs_info->sectorsize),
-						release_bytes);
+			btrfs_delalloc_release_space(inode, data_reserved,
+					round_down(pos, fs_info->sectorsize),
+					release_bytes);
 		}
 	}
 
@@ -2915,8 +2917,8 @@ static long btrfs_fallocate(struct file *file, int mode,
 			 * range, free reserved data space first, otherwise
 			 * it'll result in false ENOSPC error.
 			 */
-			btrfs_free_reserved_data_space(inode, cur_offset,
-				last_byte - cur_offset);
+			btrfs_free_reserved_data_space(inode, data_reserved,
+					cur_offset, last_byte - cur_offset);
 		}
 		free_extent_map(em);
 		cur_offset = last_byte;
@@ -2935,8 +2937,9 @@ static long btrfs_fallocate(struct file *file, int mode,
 					range->len, i_blocksize(inode),
 					offset + len, &alloc_hint);
 		else
-			btrfs_free_reserved_data_space(inode, range->start,
-						       range->len);
+			btrfs_free_reserved_data_space(inode,
+					data_reserved, range->start,
+					range->len);
 		list_del(&range->list);
 		kfree(range);
 	}
@@ -2974,8 +2977,8 @@ static long btrfs_fallocate(struct file *file, int mode,
 	inode_unlock(inode);
 	/* Let go of our reservation. */
 	if (ret != 0)
-		btrfs_free_reserved_data_space(inode, alloc_start,
-				       alloc_end - cur_offset);
+		btrfs_free_reserved_data_space(inode, data_reserved,
+				alloc_start, alloc_end - cur_offset);
 	extent_changeset_free(data_reserved);
 	return ret;
 }
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 4e211b54b267..c545aaaecb70 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -350,7 +350,7 @@ static noinline int cow_file_range_inline(struct btrfs_root *root,
 	 * And at reserve time, it's always aligned to page size, so
 	 * just free one page here.
 	 */
-	btrfs_qgroup_free_data(inode, 0, PAGE_SIZE);
+	btrfs_qgroup_free_data(inode, NULL, 0, PAGE_SIZE);
 	btrfs_free_path(path);
 	btrfs_end_transaction(trans);
 	return ret;
@@ -2933,7 +2933,7 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
 		 * space for NOCOW range.
 		 * As NOCOW won't cause a new delayed ref, just free the space
 		 */
-		btrfs_qgroup_free_data(inode, ordered_extent->file_offset,
+		btrfs_qgroup_free_data(inode, NULL, ordered_extent->file_offset,
 				       ordered_extent->len);
 		btrfs_ordered_update_i_size(inode, 0, ordered_extent);
 		if (nolock)
@@ -4792,7 +4792,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 again:
 	page = find_or_create_page(mapping, index, mask);
 	if (!page) {
-		btrfs_delalloc_release_space(inode,
+		btrfs_delalloc_release_space(inode, data_reserved,
 				round_down(from, blocksize),
 				blocksize);
 		ret = -ENOMEM;
@@ -4864,7 +4864,7 @@ int btrfs_truncate_block(struct inode *inode, loff_t from, loff_t len,
 
 out_unlock:
 	if (ret)
-		btrfs_delalloc_release_space(inode, block_start,
+		btrfs_delalloc_release_space(inode, data_reserved, block_start,
 					     blocksize);
 	unlock_page(page);
 	put_page(page);
@@ -5264,7 +5264,7 @@ static void evict_inode_truncate_pages(struct inode *inode)
 		 * Note, end is the bytenr of last byte, so we need + 1 here.
 		 */
 		if (state->state & EXTENT_DELALLOC)
-			btrfs_qgroup_free_data(inode, start, end - start + 1);
+			btrfs_qgroup_free_data(inode, NULL, start, end - start + 1);
 
 		clear_extent_bit(io_tree, start, end,
 				 EXTENT_LOCKED | EXTENT_DIRTY |
@@ -8799,8 +8799,8 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 		current->journal_info = NULL;
 		if (ret < 0 && ret != -EIOCBQUEUED) {
 			if (dio_data.reserve)
-				btrfs_delalloc_release_space(inode, offset,
-							     dio_data.reserve);
+				btrfs_delalloc_release_space(inode, data_reserved,
+					offset, dio_data.reserve);
 			/*
 			 * On error we might have left some ordered extents
 			 * without submitting corresponding bios for them, so
@@ -8815,8 +8815,8 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 					dio_data.unsubmitted_oe_range_start,
 					false);
 		} else if (ret >= 0 && (size_t)ret < count)
-			btrfs_delalloc_release_space(inode, offset,
-						     count - (size_t)ret);
+			btrfs_delalloc_release_space(inode, data_reserved,
+					offset, count - (size_t)ret);
 	}
 out:
 	if (wakeup)
@@ -9015,7 +9015,7 @@ static void btrfs_invalidatepage(struct page *page, unsigned int offset,
 	 *    free the entire extent.
 	 */
 	if (PageDirty(page))
-		btrfs_qgroup_free_data(inode, page_start, PAGE_SIZE);
+		btrfs_qgroup_free_data(inode, NULL, page_start, PAGE_SIZE);
 	if (!inode_evicting) {
 		clear_extent_bit(tree, page_start, page_end,
 				 EXTENT_LOCKED | EXTENT_DIRTY |
@@ -9137,8 +9137,8 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 			spin_lock(&BTRFS_I(inode)->lock);
 			BTRFS_I(inode)->outstanding_extents++;
 			spin_unlock(&BTRFS_I(inode)->lock);
-			btrfs_delalloc_release_space(inode, page_start,
-						PAGE_SIZE - reserved_space);
+			btrfs_delalloc_release_space(inode, data_reserved,
+					page_start, PAGE_SIZE - reserved_space);
 		}
 	}
 
@@ -9194,7 +9194,8 @@ int btrfs_page_mkwrite(struct vm_fault *vmf)
 	}
 	unlock_page(page);
 out:
-	btrfs_delalloc_release_space(inode, page_start, reserved_space);
+	btrfs_delalloc_release_space(inode, data_reserved, page_start,
+				     reserved_space);
 out_noreserve:
 	sb_end_pagefault(inode->i_sb);
 	extent_changeset_free(data_reserved);
@@ -10553,7 +10554,7 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
 			btrfs_end_transaction(trans);
 	}
 	if (cur_offset < end)
-		btrfs_free_reserved_data_space(inode, cur_offset,
+		btrfs_free_reserved_data_space(inode, NULL, cur_offset,
 			end - cur_offset + 1);
 	return ret;
 }
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a16a16a66ed9..29f8d1817a1f 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1227,7 +1227,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 		spin_lock(&BTRFS_I(inode)->lock);
 		BTRFS_I(inode)->outstanding_extents++;
 		spin_unlock(&BTRFS_I(inode)->lock);
-		btrfs_delalloc_release_space(inode,
+		btrfs_delalloc_release_space(inode, data_reserved,
 				start_index << PAGE_SHIFT,
 				(page_cnt - i_done) << PAGE_SHIFT);
 	}
@@ -1255,7 +1255,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
 		unlock_page(pages[i]);
 		put_page(pages[i]);
 	}
-	btrfs_delalloc_release_space(inode,
+	btrfs_delalloc_release_space(inode, data_reserved,
 			start_index << PAGE_SHIFT,
 			page_cnt << PAGE_SHIFT);
 	extent_changeset_free(data_reserved);
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 6086a648e67e..86366c6f2675 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2881,13 +2881,72 @@ int btrfs_qgroup_reserve_data(struct inode *inode,
 	return ret;
 }
 
-static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
-				       int free)
+/* Free ranges specified by @reserved, normally in error path */
+static int qgroup_free_reserved_data(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct ulist_node *unode;
+	struct ulist_iterator uiter;
+	struct extent_changeset changeset;
+	int freed = 0;
+	int ret;
+
+	extent_changeset_init(&changeset);
+	len = round_up(start + len, root->fs_info->sectorsize);
+	start = round_down(start, root->fs_info->sectorsize);
+
+	ULIST_ITER_INIT(&uiter);
+	while ((unode = ulist_next(&reserved->range_changed, &uiter))) {
+		u64 range_start = unode->val;
+		/* unode->aux is the inclusive end */
+		u64 range_len = unode->aux - range_start + 1;
+		u64 free_start;
+		u64 free_len;
+
+		extent_changeset_release(&changeset);
+
+		/* Only free range in range [start, start + len) */
+		if (range_start >= start + len ||
+		    range_start + range_len <= start)
+			continue;
+		free_start = max(range_start, start);
+		free_len = min(start + len, range_start + range_len) -
+			   free_start;
+		/*
+		 * TODO: To also modify reserved->ranges_reserved to reflect
+		 * the modification.
+		 *
+		 * However as long as we free qgroup reserved according to
+		 * EXTENT_QGROUP_RESERVED, we won't double free.
+		 * So not need to rush.
+		 */
+		ret = clear_record_extent_bits(&BTRFS_I(inode)->io_failure_tree,
+				free_start, free_start + free_len - 1,
+				EXTENT_QGROUP_RESERVED, &changeset);
+		if (ret < 0)
+			goto out;
+		freed += changeset.bytes_changed;
+	}
+	btrfs_qgroup_free_refroot(root->fs_info, root->objectid, freed);
+	ret = freed;
+out:
+	extent_changeset_release(&changeset);
+	return ret;
+}
+
+static int __btrfs_qgroup_release_data(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len,
+			int free)
 {
 	struct extent_changeset changeset;
 	int trace_op = QGROUP_RELEASE;
 	int ret;
 
+	/* In release case, we shouldn't have @reserved */
+	WARN_ON(!free && reserved);
+	if (free && reserved)
+		return qgroup_free_reserved_data(inode, reserved, start, len);
 	extent_changeset_init(&changeset);
 	ret = clear_record_extent_bits(&BTRFS_I(inode)->io_tree, start, 
 			start + len -1, EXTENT_QGROUP_RESERVED, &changeset);
@@ -2913,14 +2972,17 @@ static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
  *
  * Should be called when a range of pages get invalidated before reaching disk.
  * Or for error cleanup case.
+ * if @reserved is given, only reserved range in [@start, @start + @len) will
+ * be freed.
  *
  * For data written to disk, use btrfs_qgroup_release_data().
  *
  * NOTE: This function may sleep for memory allocation.
  */
-int btrfs_qgroup_free_data(struct inode *inode, u64 start, u64 len)
+int btrfs_qgroup_free_data(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len)
 {
-	return __btrfs_qgroup_release_data(inode, start, len, 1);
+	return __btrfs_qgroup_release_data(inode, reserved, start, len, 1);
 }
 
 /*
@@ -2940,7 +3002,7 @@ int btrfs_qgroup_free_data(struct inode *inode, u64 start, u64 len)
  */
 int btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len)
 {
-	return __btrfs_qgroup_release_data(inode, start, len, 0);
+	return __btrfs_qgroup_release_data(inode, NULL, start, len, 0);
 }
 
 int btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes,
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
index c7a2bcaff5d5..102aa7fb342b 100644
--- a/fs/btrfs/qgroup.h
+++ b/fs/btrfs/qgroup.h
@@ -244,7 +244,8 @@ int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
 int btrfs_qgroup_reserve_data(struct inode *inode,
 			struct extent_changeset **reserved, u64 start, u64 len);
 int btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len);
-int btrfs_qgroup_free_data(struct inode *inode, u64 start, u64 len);
+int btrfs_qgroup_free_data(struct inode *inode,
+			struct extent_changeset *reserved, u64 start, u64 len);
 
 int btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes,
 			      bool enforce);
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 5823e2d67a84..2115f3e02dd5 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3114,8 +3114,8 @@ int prealloc_file_extent_cluster(struct inode *inode,
 		lock_extent(&BTRFS_I(inode)->io_tree, start, end);
 		num_bytes = end + 1 - start;
 		if (cur_offset < start)
-			btrfs_free_reserved_data_space(inode, cur_offset,
-					start - cur_offset);
+			btrfs_free_reserved_data_space(inode, data_reserved,
+					cur_offset, start - cur_offset);
 		ret = btrfs_prealloc_file_range(inode, 0, start,
 						num_bytes, num_bytes,
 						end + 1, &alloc_hint);
@@ -3126,8 +3126,8 @@ int prealloc_file_extent_cluster(struct inode *inode,
 		nr++;
 	}
 	if (cur_offset < prealloc_end)
-		btrfs_free_reserved_data_space(inode, cur_offset,
-				       prealloc_end + 1 - cur_offset);
+		btrfs_free_reserved_data_space(inode, data_reserved,
+				cur_offset, prealloc_end + 1 - cur_offset);
 out:
 	inode_unlock(inode);
 	extent_changeset_free(data_reserved);
-- 
2.12.2

Re: [RFC PATCH v3.1 1/6] btrfs: qgroup: Add quick exit for non-fs extents

[David Sterba]

On Fri, May 12, 2017 at 11:30:41AM +0800, Qu Wenruo wrote:
> For btrfs_qgroup_account_extent(), modify make it exit quicker for
> non-fs extents.

A short explanation why this is ok would be desired here.

Re: [RFC PATCH v3.1 3/6] btrfs: qgroup: Return actually freed bytes for qgroup release or free data

[David Sterba]

On Fri, May 12, 2017 at 11:30:43AM +0800, Qu Wenruo wrote:
> btrfs_qgroup_release/free_data() only returns 0 or minus error
> number(ENOMEM is the only possible error).

"btrfs_qgroup_release/free_data() only returns 0 or a negative error
number (ENOMEM is the only possible error)."

> This is normally good enough, but sometimes we need the accurate byte
> number it freed/released.
> 
> Change it to return actually released/freed bytenr number instead of 0
> for success.
> And slightly modify related extent_changeset structure, since in btrfs
> one none-hole data extent won't be larger than 128M, so "unsigned int"
      ^^^^^^^^^
      NO_HOLES or no-hole

> is large enough for the use case.
> 
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> ---
>  fs/btrfs/extent-tree.c | 2 +-
>  fs/btrfs/extent_io.h   | 2 +-
>  fs/btrfs/qgroup.c      | 1 +
>  3 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index e390451c72e6..4f62696131a6 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -4298,7 +4298,7 @@ int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len)
>  
>  	/* Use new btrfs_qgroup_reserve_data to reserve precious data space. */
>  	ret = btrfs_qgroup_reserve_data(inode, start, len);
> -	if (ret)
> +	if (ret < 0)
>  		btrfs_free_reserved_data_space_noquota(inode, start, len);
>  	return ret;
>  }
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index 1eafa2f0ede3..cc1b08fa9fe7 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -205,7 +205,7 @@ struct extent_buffer {
>   */
>  struct extent_changeset {
>  	/* How many bytes are set/cleared in this operation */
> -	u64 bytes_changed;
> +	unsigned int bytes_changed;

The alignment constraints will insert 4 bytes anyway, so we don't save
any space, but unsigned int is fine here, as we're not going to utilize u64.

>  	/* Changed ranges */
>  	struct ulist range_changed;
> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> index 9f01c25469f7..ad2e99491395 100644
> --- a/fs/btrfs/qgroup.c
> +++ b/fs/btrfs/qgroup.c
> @@ -2886,6 +2886,7 @@ static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
>  		btrfs_qgroup_free_refroot(BTRFS_I(inode)->root->fs_info,
>  				BTRFS_I(inode)->root->objectid,
>  				changeset.bytes_changed);
> +	ret = changeset.bytes_changed;
>  out:
>  	ulist_release(&changeset.range_changed);
>  	return ret;
> -- 
> 2.12.2
> 
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [RFC PATCH v3.1 3/6] btrfs: qgroup: Return actually freed bytes for qgroup release or free data

[Qu Wenruo]

At 05/16/2017 10:23 PM, David Sterba wrote:
> On Fri, May 12, 2017 at 11:30:43AM +0800, Qu Wenruo wrote:
>> btrfs_qgroup_release/free_data() only returns 0 or minus error
>> number(ENOMEM is the only possible error).
> 
> "btrfs_qgroup_release/free_data() only returns 0 or a negative error
> number (ENOMEM is the only possible error)." >
>> This is normally good enough, but sometimes we need the accurate byte
>> number it freed/released.
>>
>> Change it to return actually released/freed bytenr number instead of 0
>> for success.
>> And slightly modify related extent_changeset structure, since in btrfs
>> one none-hole data extent won't be larger than 128M, so "unsigned int"
>        ^^^^^^^^^
>        NO_HOLES or no-hole
> 
>> is large enough for the use case.
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>> ---
>>   fs/btrfs/extent-tree.c | 2 +-
>>   fs/btrfs/extent_io.h   | 2 +-
>>   fs/btrfs/qgroup.c      | 1 +
>>   3 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>> index e390451c72e6..4f62696131a6 100644
>> --- a/fs/btrfs/extent-tree.c
>> +++ b/fs/btrfs/extent-tree.c
>> @@ -4298,7 +4298,7 @@ int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len)
>>   
>>   	/* Use new btrfs_qgroup_reserve_data to reserve precious data space. */
>>   	ret = btrfs_qgroup_reserve_data(inode, start, len);
>> -	if (ret)
>> +	if (ret < 0)
>>   		btrfs_free_reserved_data_space_noquota(inode, start, len);
>>   	return ret;
>>   }
>> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
>> index 1eafa2f0ede3..cc1b08fa9fe7 100644
>> --- a/fs/btrfs/extent_io.h
>> +++ b/fs/btrfs/extent_io.h
>> @@ -205,7 +205,7 @@ struct extent_buffer {
>>    */
>>   struct extent_changeset {
>>   	/* How many bytes are set/cleared in this operation */
>> -	u64 bytes_changed;
>> +	unsigned int bytes_changed;
> 
> The alignment constraints will insert 4 bytes anyway, so we don't save
> any space, but unsigned int is fine here, as we're not going to utilize u64.

Sorry, I just realized that extent_state in extent_io_tree can be merged 
with each other.

So (state->end - state->start + 1) can overflow unsigned int.

I'll skip this modification in next update, and apply the grammar comment.

Thanks,
Qu

> 
>>   	/* Changed ranges */
>>   	struct ulist range_changed;
>> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
>> index 9f01c25469f7..ad2e99491395 100644
>> --- a/fs/btrfs/qgroup.c
>> +++ b/fs/btrfs/qgroup.c
>> @@ -2886,6 +2886,7 @@ static int __btrfs_qgroup_release_data(struct inode *inode, u64 start, u64 len,
>>   		btrfs_qgroup_free_refroot(BTRFS_I(inode)->root->fs_info,
>>   				BTRFS_I(inode)->root->objectid,
>>   				changeset.bytes_changed);
>> +	ret = changeset.bytes_changed;
>>   out:
>>   	ulist_release(&changeset.range_changed);
>>   	return ret;
>> -- 
>> 2.12.2
>>
>>
>>
>> --
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> --
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> 
> 

Re: [RFC PATCH v3.1 3/6] btrfs: qgroup: Return actually freed bytes for qgroup release or free data

[Qu Wenruo]

At 05/17/2017 09:12 AM, Qu Wenruo wrote:
> 
> 
> At 05/16/2017 10:23 PM, David Sterba wrote:
>> On Fri, May 12, 2017 at 11:30:43AM +0800, Qu Wenruo wrote:
>>> btrfs_qgroup_release/free_data() only returns 0 or minus error
>>> number(ENOMEM is the only possible error).
>>
>> "btrfs_qgroup_release/free_data() only returns 0 or a negative error
>> number (ENOMEM is the only possible error)." >
>>> This is normally good enough, but sometimes we need the accurate byte
>>> number it freed/released.
>>>
>>> Change it to return actually released/freed bytenr number instead of 0
>>> for success.
>>> And slightly modify related extent_changeset structure, since in btrfs
>>> one none-hole data extent won't be larger than 128M, so "unsigned int"
>>        ^^^^^^^^^
>>        NO_HOLES or no-hole
>>
>>> is large enough for the use case.
>>>
>>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>>> ---
>>>   fs/btrfs/extent-tree.c | 2 +-
>>>   fs/btrfs/extent_io.h   | 2 +-
>>>   fs/btrfs/qgroup.c      | 1 +
>>>   3 files changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>>> index e390451c72e6..4f62696131a6 100644
>>> --- a/fs/btrfs/extent-tree.c
>>> +++ b/fs/btrfs/extent-tree.c
>>> @@ -4298,7 +4298,7 @@ int btrfs_check_data_free_space(struct inode 
>>> *inode, u64 start, u64 len)
>>>       /* Use new btrfs_qgroup_reserve_data to reserve precious data 
>>> space. */
>>>       ret = btrfs_qgroup_reserve_data(inode, start, len);
>>> -    if (ret)
>>> +    if (ret < 0)
>>>           btrfs_free_reserved_data_space_noquota(inode, start, len);
>>>       return ret;
>>>   }
>>> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
>>> index 1eafa2f0ede3..cc1b08fa9fe7 100644
>>> --- a/fs/btrfs/extent_io.h
>>> +++ b/fs/btrfs/extent_io.h
>>> @@ -205,7 +205,7 @@ struct extent_buffer {
>>>    */
>>>   struct extent_changeset {
>>>       /* How many bytes are set/cleared in this operation */
>>> -    u64 bytes_changed;
>>> +    unsigned int bytes_changed;
>>
>> The alignment constraints will insert 4 bytes anyway, so we don't save
>> any space, but unsigned int is fine here, as we're not going to 
>> utilize u64.
> 
> Sorry, I just realized that extent_state in extent_io_tree can be merged 
> with each other.
> 
> So (state->end - state->start + 1) can overflow unsigned int.

Please ignore this comment.
In context of btrfs_qgroup_reserve_data(), we won't modify ranges out of 
the data extent, which is no larger than 128M.

And all related extent_changeset users are all based on actually 
allocated extent, so we won't overflow unsigned int any way.

Thanks,
Qu

> 
> I'll skip this modification in next update, and apply the grammar comment.
> 
> Thanks,
> Qu
> 
>>
>>>       /* Changed ranges */
>>>       struct ulist range_changed;
>>> diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
>>> index 9f01c25469f7..ad2e99491395 100644
>>> --- a/fs/btrfs/qgroup.c
>>> +++ b/fs/btrfs/qgroup.c
>>> @@ -2886,6 +2886,7 @@ static int __btrfs_qgroup_release_data(struct 
>>> inode *inode, u64 start, u64 len,
>>>           btrfs_qgroup_free_refroot(BTRFS_I(inode)->root->fs_info,
>>>                   BTRFS_I(inode)->root->objectid,
>>>                   changeset.bytes_changed);
>>> +    ret = changeset.bytes_changed;
>>>   out:
>>>       ulist_release(&changeset.range_changed);
>>>       return ret;
>>> -- 
>>> 2.12.2
>>>
>>>
>>>
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>>