[PATCH v4 00/13] btrfs: scrub: use a more reader friendly code to implement scrub_simple_mirror()

[PATCH v4 00/13] btrfs: scrub: use a more reader friendly code to implement scrub_simple_mirror()

[Qu Wenruo]

This series can be found in my github repo:

https://github.com/adam900710/linux/tree/scrub_stripe

It's recommended to fetch from the repo, as our misc-next seems to
change pretty rapidly.

[Changelog]
v4:
- Add a dedicated patch to add btrfs_bio::fs_info
  Along with dedicated allocator for scrub btrfs bios.
  The dedicated allocator is due to the fact that scrub and regular
  btrfs bios have very different mandatory members (fs_info vs inode +
  file_offset).
  For now I believe a different allocator would be better.

- Some code style change
  * No more single letter temporray structure copied from old scrub code
  * Use "for (int i = 0; ...)" when possible
  * Some new lines fixes
  * Extra brackets for tenrary operators
  * A new macro for (BTRFS_STRIPE_LEN >> PAGE_SHIFT)
  * Use enum for scrub_stripe::state bit flags
  * Use extra brackets for double shifting
  * Use explicit != 0 or == 0 comparing memcmp() results
  * Remove unnecessary ASSERT()s after btrfs_bio allocation

v3:
- Add a dedicated @fs_info member for btrfs_bio
  Unfortunately although we have a 32 bytes hole between @end_io_work and @bio,
  compiler still choose not to use that hole for whatever reasons.
  Thus this would increase the size of btrfs_bio by 4 bytes.

- Rebased to lastest misc-next

- Fix various while space error not caught by btrfs-workflow

v2:
- Use batched scrub_stripe submission
  This allows much better performance compared to the old scrub code

- Add scrub specific bio layer helpers
  This makes the scrub code to be completely rely on logical bytenr +
  mirror_num.

[PROBLEMS OF OLD SCRUB]

- Too many delayed jumps, making it hard to read
  Even starting from scrub_simple_mirror(), we have the following
  functions:

  scrub_extent()
       |
       v
  scrub_sectors()
       |
       v
  scrub_add_sector_to_rd_bio()
       | endio function
       v
  scrub_bio_end_io()
       | delayed work
       v
  scrub_bio_end_io_worker()
       |
       v
  scrub_block_complete()
       |
       v
  scrub_handle_errored_blocks()
       |
       v
  scrub_recheck_block()
       |
       v
  scrub_repair_sector_from_good_copy()

  Not to mention the hidden jumps in certain branches.

- IOPS inefficient for fragmented extents

  The real block size of scrub read is between 4K and 128K.
  If the extents are not adjacent, the blocksize drops to 4K and would
  be an IOPS disaster.

- All hardcoded to do the logical -> physical mapping by scrub itself
  No usage of any existing bio facilities.
  And even implemented a RAID56 recovery wrapper.

[NEW SCRUB_STRIPE BASED SOLUTION]

- Overall streamlined code base

  queue_scrub_stripe()
     |
     v
  scrub_find_fill_first_stripe()
     |
     v
  done

  Or

  queue_scrub_stripe()
     |
     v
  flush_scrub_stripes()
     |
     v
  scrub_submit_initial_read()
     | endio function
     v
  scrub_read_endio()
     | delayed work
     v
  scrub_stripe_read_repair_worker()
     |
     v
  scrub_verify_one_stripe()
     |
     v
  scrub_stripe_submit_repair_read()
     |
     v
  scrub_write_sectors()
     |
     v
  scrub_stripe_report_errors()

  Only one endio and delayed work, all other work are properly done in a
  sequential workflow.

- Always read in 64KiB block size
  The real blocksize of read starts at 64KiB, and ends at 512K.
  This already results a better performance even for the worst case:

  With patchset:	404.81MiB/s
  Without patchset:	369.30MiB/s

  Around 10% performance improvement on an SATA SSD.

- All logical bytenr/mirror_num based read and write

  With the new single stripe fast path in btrfs_submit_bio(), scrub can
  reuse most of the bio layer code, result much simpler scrub code.

[TODO]

- More testing on zoned devices
  Now the patchset can already pass all scrub/replace groups with
  regular devices.

- More cleanup on RAID56 path
  Now RAID56 still uses some old facility, resulting things like
  scrub_sector and scrub_bio can not be fully cleaned up.

Qu Wenruo (13):
  btrfs: scrub: use dedicated super block verification function to scrub
    one super block
  btrfs: introduce a new allocator for scrub specific btrfs_bio
  btrfs: introduce a new helper to submit read bio for scrub
  btrfs: introduce a new helper to submit write bio for scrub
  btrfs: scrub: introduce the structure for new BTRFS_STRIPE_LEN based
    interface
  btrfs: scrub: introduce a helper to find and fill the sector info for
    a scrub_stripe
  btrfs: scrub: introduce a helper to verify one metadata
  btrfs: scrub: introduce a helper to verify one scrub_stripe
  btrfs: scrub: introduce the main read repair worker for scrub_stripe
  btrfs: scrub: introduce a writeback helper for scrub_stripe
  btrfs: scrub: introduce error reporting functionality for scrub_stripe
  btrfs: scrub: introduce the helper to queue a stripe for scrub
  btrfs: scrub: switch scrub_simple_mirror() to scrub_stripe
    infrastructure

 fs/btrfs/bio.c       |  165 ++++-
 fs/btrfs/bio.h       |   22 +-
 fs/btrfs/file-item.c |    9 +-
 fs/btrfs/file-item.h |    3 +-
 fs/btrfs/raid56.c    |    2 +-
 fs/btrfs/scrub.c     | 1654 ++++++++++++++++++++++++++++++------------
 6 files changed, 1370 insertions(+), 485 deletions(-)

-- 
2.39.2

[PATCH v4 01/13] btrfs: scrub: use dedicated super block verification function to scrub one super block

[Qu Wenruo]

There is really no need to go through the super complex scrub_sectors()
to just handle super blocks.

This patch will introduce a dedicated function (less than 50 lines) to
handle super block scrubing.

This new function will introduce a behavior change, instead of using the
complex but concurrent scrub_bio system, here we just go
submit-and-wait.

There is really not much sense to care the performance of super block
scrubbing. It only has 3 super blocks at most, and they are all scattered
around the devices already.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 54 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 3cdf73277e7e..e765eb8b8bcf 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -4243,18 +4243,59 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
 	return ret;
 }
 
+static int scrub_one_super(struct scrub_ctx *sctx, struct btrfs_device *dev,
+			   struct page *page, u64 physical, u64 generation)
+{
+	struct btrfs_fs_info *fs_info = sctx->fs_info;
+	struct bio_vec bvec;
+	struct bio bio;
+	struct btrfs_super_block *sb = page_address(page);
+	int ret;
+
+	bio_init(&bio, dev->bdev, &bvec, 1, REQ_OP_READ);
+	bio.bi_iter.bi_sector = physical >> SECTOR_SHIFT;
+	bio_add_page(&bio, page, BTRFS_SUPER_INFO_SIZE, 0);
+	ret = submit_bio_wait(&bio);
+	bio_uninit(&bio);
+
+	if (ret < 0)
+		return ret;
+	ret = btrfs_check_super_csum(fs_info, sb);
+	if (ret != 0) {
+		btrfs_err_rl(fs_info,
+			"super block at physical %llu devid %llu has bad csum",
+			physical, dev->devid);
+		return -EIO;
+	}
+	if (btrfs_super_generation(sb) != generation) {
+		btrfs_err_rl(fs_info,
+"super block at physical %llu devid %llu has bad generation, has %llu expect %llu",
+			     physical, dev->devid,
+			     btrfs_super_generation(sb), generation);
+		return -EUCLEAN;
+	}
+
+	ret = btrfs_validate_super(fs_info, sb, -1);
+	return ret;
+}
+
 static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx,
 					   struct btrfs_device *scrub_dev)
 {
 	int	i;
 	u64	bytenr;
 	u64	gen;
-	int	ret;
+	int	ret = 0;
+	struct page *page;
 	struct btrfs_fs_info *fs_info = sctx->fs_info;
 
 	if (BTRFS_FS_ERROR(fs_info))
 		return -EROFS;
 
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
 	/* Seed devices of a new filesystem has their own generation. */
 	if (scrub_dev->fs_devices != fs_info->fs_devices)
 		gen = scrub_dev->generation;
@@ -4269,15 +4310,12 @@ static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx,
 		if (!btrfs_check_super_location(scrub_dev, bytenr))
 			continue;
 
-		ret = scrub_sectors(sctx, bytenr, BTRFS_SUPER_INFO_SIZE, bytenr,
-				    scrub_dev, BTRFS_EXTENT_FLAG_SUPER, gen, i,
-				    NULL, bytenr);
+		ret = scrub_one_super(sctx, scrub_dev, page, bytenr, gen);
 		if (ret)
-			return ret;
+			break;
 	}
-	wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
-
-	return 0;
+	__free_page(page);
+	return ret;
 }
 
 static void scrub_workers_put(struct btrfs_fs_info *fs_info)
-- 
2.39.2

Re: [PATCH v4 01/13] btrfs: scrub: use dedicated super block verification function to scrub one super block

[Christoph Hellwig]

On Sun, Mar 26, 2023 at 07:06:30PM +0800, Qu Wenruo wrote:
> There is really no need to go through the super complex scrub_sectors()
> to just handle super blocks.
> 
> This patch will introduce a dedicated function (less than 50 lines) to
> handle super block scrubing.
> 
> This new function will introduce a behavior change, instead of using the
> complex but concurrent scrub_bio system, here we just go
> submit-and-wait.
> 
> There is really not much sense to care the performance of super block
> scrubbing. It only has 3 super blocks at most, and they are all scattered
> around the devices already.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/scrub.c | 54 +++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 46 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 3cdf73277e7e..e765eb8b8bcf 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -4243,18 +4243,59 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
>  	return ret;
>  }
>  
> +static int scrub_one_super(struct scrub_ctx *sctx, struct btrfs_device *dev,
> +			   struct page *page, u64 physical, u64 generation)
> +{
> +	struct btrfs_fs_info *fs_info = sctx->fs_info;
> +	struct bio_vec bvec;
> +	struct bio bio;
> +	struct btrfs_super_block *sb = page_address(page);
> +	int ret;
> +
> +	bio_init(&bio, dev->bdev, &bvec, 1, REQ_OP_READ);
> +	bio.bi_iter.bi_sector = physical >> SECTOR_SHIFT;
> +	bio_add_page(&bio, page, BTRFS_SUPER_INFO_SIZE, 0);

bio_add_page wants its return value checked.  Now here we obviously
don't need that, but please just use __bio_add_page which has the
proper assert for that.

[PATCH v4 02/13] btrfs: introduce a new allocator for scrub specific btrfs_bio

[Qu Wenruo]

Currently we're doing a lot of work for btrfs_bio:

- Checksum verification for data read bios
- Bio splits if it crosses stripe boundary
- Read repair for data read bios

However for the incoming scrub patches, we don't want those extra
functionality at all, just pure logical + mirror -> physical mapping
ability.

Thus here we introduce:

- btrfs_bio::fs_info
  This is for the new scrub specific btrfs_bio, which would not
  populate btrfs_bio::inode.
  Thus we need such new member to grab a fs_info

  This new member would always be populated.

- btrfs_scrub_bio_alloc() helper
  The main differences between this and btrfs_bio_alloc() are:
  * No need for nr_vecs
    As we know scrub bio should not cross stripe boundary.

  * Use @fs_info to replace @inode parameter

- An extra ASSERT() to make sure btrfs_bio::fs_info is populated

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/bio.c | 25 +++++++++++++++++++++++++
 fs/btrfs/bio.h | 19 ++++++++++++++++++-
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
index cf09c6271edb..c1edadc17260 100644
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -36,6 +36,7 @@ void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_inode *inode,
 {
 	memset(bbio, 0, offsetof(struct btrfs_bio, bio));
 	bbio->inode = inode;
+	bbio->fs_info = inode->root->fs_info;
 	bbio->end_io = end_io;
 	bbio->private = private;
 	atomic_set(&bbio->pending_ios, 1);
@@ -61,6 +62,30 @@ struct btrfs_bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
 	return bbio;
 }
 
+/*
+ * Allocate a scrub specific btrfs_bio structure.
+ *
+ * This btrfs_bio would not go through any the btrfs special handling like
+ * checksum verification nor read-repair.
+ */
+struct btrfs_bio *btrfs_scrub_bio_alloc(blk_opf_t opf,
+					struct btrfs_fs_info *fs_info,
+					btrfs_bio_end_io_t end_io, void *private)
+{
+	struct btrfs_bio *bbio;
+	struct bio *bio;
+
+	bio = bio_alloc_bioset(NULL, BTRFS_STRIPE_LEN >> fs_info->sectorsize_bits,
+			       opf, GFP_NOFS, &btrfs_bioset);
+	bbio = btrfs_bio(bio);
+	memset(bbio, 0, offsetof(struct btrfs_bio, bio));
+	bbio->fs_info = fs_info;
+	bbio->end_io = end_io;
+	bbio->private = private;
+	atomic_set(&bbio->pending_ios, 1);
+	return bbio;
+}
+
 static struct btrfs_bio *btrfs_split_bio(struct btrfs_fs_info *fs_info,
 					 struct btrfs_bio *orig_bbio,
 					 u64 map_length, bool use_append)
diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h
index dbf125f6fa33..3b97ce54140a 100644
--- a/fs/btrfs/bio.h
+++ b/fs/btrfs/bio.h
@@ -30,7 +30,12 @@ typedef void (*btrfs_bio_end_io_t)(struct btrfs_bio *bbio);
  * passed to btrfs_submit_bio for mapping to the physical devices.
  */
 struct btrfs_bio {
-	/* Inode and offset into it that this I/O operates on. */
+	/*
+	 * Inode and offset into it that this I/O operates on.
+	 *
+	 * @inode can be NULL for callers who don't want any advanced features
+	 * like read-time repair.
+	 */
 	struct btrfs_inode *inode;
 	u64 file_offset;
 
@@ -58,6 +63,15 @@ struct btrfs_bio {
 	atomic_t pending_ios;
 	struct work_struct end_io_work;
 
+	/*
+	 * For cases where callers only want to read/write from a logical
+	 * bytenr, in that case @inode can be NULL, and we need such
+	 * @fs_info pointer to grab the corresponding fs_info.
+	 *
+	 * Should always be populated.
+	 */
+	struct btrfs_fs_info *fs_info;
+
 	/*
 	 * This member must come last, bio_alloc_bioset will allocate enough
 	 * bytes for entire btrfs_bio but relies on bio being last.
@@ -78,6 +92,9 @@ void btrfs_bio_init(struct btrfs_bio *bbio, struct btrfs_inode *inode,
 struct btrfs_bio *btrfs_bio_alloc(unsigned int nr_vecs, blk_opf_t opf,
 				  struct btrfs_inode *inode,
 				  btrfs_bio_end_io_t end_io, void *private);
+struct btrfs_bio *btrfs_scrub_bio_alloc(blk_opf_t opf,
+					struct btrfs_fs_info *fs_info,
+					btrfs_bio_end_io_t end_io, void *private);
 
 static inline void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status)
 {
-- 
2.39.2

Re: [PATCH v4 02/13] btrfs: introduce a new allocator for scrub specific btrfs_bio

[Christoph Hellwig]

I'd still prefer to just change the btrfs_bio_init / btrfs_bio_alloc
prototype changes we discussed.  But if we need to rush this series
in I can fix it up later.

[PATCH v4 03/13] btrfs: introduce a new helper to submit read bio for scrub

[Qu Wenruo]

The new helper, btrfs_submit_scrub_read(), would be mostly a subset of
btrfs_submit_bio(), with the following limitations:

- Only supports read
- @mirror_num must be > 0
- No read-time repair nor checksum verification
- The @bbio must not cross stripe boundary

This would provide the basis for unified read repair for scrub, as we no
longer needs to handle RAID56 recovery all by scrub, and RAID56 data
stripes scrub can share the same code of read and repair.

The repair part would be the same as non-RAID56, as we only need to try
the next mirror.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/bio.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
 fs/btrfs/bio.h |  1 +
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
index c1edadc17260..bdef346c542c 100644
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -333,8 +333,8 @@ static void btrfs_end_bio_work(struct work_struct *work)
 {
 	struct btrfs_bio *bbio = container_of(work, struct btrfs_bio, end_io_work);
 
-	/* Metadata reads are checked and repaired by the submitter. */
-	if (bbio->bio.bi_opf & REQ_META)
+	/* Metadata or scrub reads are checked and repaired by the submitter. */
+	if (bbio->bio.bi_opf & REQ_META || !bbio->inode)
 		bbio->end_io(bbio);
 	else
 		btrfs_check_read_bio(bbio, bbio->bio.bi_private);
@@ -344,7 +344,7 @@ static void btrfs_simple_end_io(struct bio *bio)
 {
 	struct btrfs_bio *bbio = btrfs_bio(bio);
 	struct btrfs_device *dev = bio->bi_private;
-	struct btrfs_fs_info *fs_info = bbio->inode->root->fs_info;
+	struct btrfs_fs_info *fs_info = bbio->fs_info;
 
 	btrfs_bio_counter_dec(fs_info);
 
@@ -368,7 +368,8 @@ static void btrfs_raid56_end_io(struct bio *bio)
 
 	btrfs_bio_counter_dec(bioc->fs_info);
 	bbio->mirror_num = bioc->mirror_num;
-	if (bio_op(bio) == REQ_OP_READ && !(bbio->bio.bi_opf & REQ_META))
+	if (bio_op(bio) == REQ_OP_READ && bbio->inode &&
+	    !(bbio->bio.bi_opf & REQ_META))
 		btrfs_check_read_bio(bbio, NULL);
 	else
 		btrfs_orig_bbio_end_io(bbio);
@@ -714,6 +715,45 @@ static bool btrfs_submit_chunk(struct btrfs_bio *bbio, int mirror_num)
 	return true;
 }
 
+/*
+ * Scrub read special version, with extra limits:
+ *
+ * - Only support read for scrub usage
+ * - @mirror_num must be >0
+ * - No read-time repair nor checksum verification.
+ * - The @bbio must not cross stripe boundary.
+ */
+void btrfs_submit_scrub_read(struct btrfs_bio *bbio, int mirror_num)
+{
+	struct btrfs_fs_info *fs_info = bbio->fs_info;
+	u64 logical = bbio->bio.bi_iter.bi_sector << SECTOR_SHIFT;
+	u64 length = bbio->bio.bi_iter.bi_size;
+	u64 map_length = length;
+	struct btrfs_io_context *bioc = NULL;
+	struct btrfs_io_stripe smap;
+	int ret;
+
+	ASSERT(fs_info);
+	ASSERT(mirror_num > 0);
+	ASSERT(btrfs_op(&bbio->bio) == BTRFS_MAP_READ);
+	ASSERT(!bbio->inode);
+
+	btrfs_bio_counter_inc_blocked(fs_info);
+	ret = __btrfs_map_block(fs_info, btrfs_op(&bbio->bio), logical,
+				&map_length, &bioc, &smap, &mirror_num, 1);
+	if (ret)
+		goto fail;
+
+	/* Caller should ensure the @bbio doesn't cross stripe boundary. */
+	ASSERT(map_length >= length);
+	__btrfs_submit_bio(&bbio->bio, bioc, &smap, mirror_num);
+	return;
+
+fail:
+	btrfs_bio_counter_dec(fs_info);
+	btrfs_bio_end_io(bbio, errno_to_blk_status(ret));
+}
+
 void btrfs_submit_bio(struct btrfs_bio *bbio, int mirror_num)
 {
 	while (!btrfs_submit_chunk(bbio, mirror_num))
diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h
index 3b97ce54140a..afbcf318fdda 100644
--- a/fs/btrfs/bio.h
+++ b/fs/btrfs/bio.h
@@ -106,6 +106,7 @@ static inline void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status)
 #define REQ_BTRFS_ONE_ORDERED			REQ_DRV
 
 void btrfs_submit_bio(struct btrfs_bio *bbio, int mirror_num);
+void btrfs_submit_scrub_read(struct btrfs_bio *bbio, int mirror_num);
 int btrfs_repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
 			    u64 length, u64 logical, struct page *page,
 			    unsigned int pg_offset, int mirror_num);
-- 
2.39.2

[PATCH v4 04/13] btrfs: introduce a new helper to submit write bio for scrub

[Qu Wenruo]

Just like the special scrub read, scrub write also has its extra niches:

- Only write back to single device
  Even for read-repair on RAID56, we only update the corrupted data
  stripe itself, not triggering the full RMW path.

  This makes scrub writeback a perfect match for the single stripe
  quick path.

- Requires a valid @mirror_num
  For RAID56 case, only @mirror_num == 1 is supported.
  For non-RAID56 cases, we need @mirror_num to locate our stripe.

- Need to manually specify if it's for dev-replace
  For scrub path we can write back to the original device (for
  read-repair) and to the target device (for replace) at the same
  time, but with different sectors (read-repair only writes repaired
  sectors, while dev-replace writes all good sectors).

  So here we need a bool to specify the case.

- No data csum generation

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/bio.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/bio.h |  2 ++
 2 files changed, 94 insertions(+)

diff --git a/fs/btrfs/bio.c b/fs/btrfs/bio.c
index bdef346c542c..34902d58bb4b 100644
--- a/fs/btrfs/bio.c
+++ b/fs/btrfs/bio.c
@@ -754,6 +754,98 @@ void btrfs_submit_scrub_read(struct btrfs_bio *bbio, int mirror_num)
 	btrfs_bio_end_io(bbio, errno_to_blk_status(ret));
 }
 
+/*
+ * Scrub write special version. Some extra limits:
+ *
+ * - Only support write back for dev-replace and scrub read-repair.
+ *   This means, the write bio, even for RAID56, would only
+ *   be mapped to single device.
+ *
+ * - @mirror_num must be >0.
+ *   To indicate which mirror to be written.
+ *   If it's RAID56, it must be 1 (data stripes).
+ *
+ * - The @bbio must not cross stripe boundary.
+ *
+ * - If @dev_replace is true, the resulted stripe must be mapped to
+ *   replace source device.
+ *
+ * - No csum geneartion.
+ */
+void btrfs_submit_scrub_write(struct btrfs_bio *bbio, int mirror_num,
+			      bool dev_replace)
+{
+	struct btrfs_fs_info *fs_info = bbio->fs_info;
+	u64 logical = bbio->bio.bi_iter.bi_sector << SECTOR_SHIFT;
+	u64 length = bbio->bio.bi_iter.bi_size;
+	u64 map_length = length;
+	struct btrfs_io_context *bioc = NULL;
+	struct btrfs_io_stripe smap;
+	int ret;
+
+	ASSERT(fs_info);
+	ASSERT(mirror_num > 0);
+	ASSERT(btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE);
+	ASSERT(!bbio->inode);
+
+	btrfs_bio_counter_inc_blocked(fs_info);
+	ret = __btrfs_map_block(fs_info, btrfs_op(&bbio->bio), logical,
+				&map_length, &bioc, &smap, &mirror_num, 1);
+	if (ret)
+		goto fail;
+
+	/* Caller should ensure the @bbio doesn't cross stripe boundary. */
+	ASSERT(map_length >= length);
+	if (btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE && btrfs_is_zoned(fs_info)) {
+		bbio->bio.bi_opf &= ~REQ_OP_WRITE;
+		bbio->bio.bi_opf |= REQ_OP_ZONE_APPEND;
+	}
+
+	if (!bioc)
+		goto submit;
+
+	/* Map the RAID56 multi-stripe writes to a single one. */
+	if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
+		int data_stripes = (bioc->map_type & BTRFS_BLOCK_GROUP_RAID5) ?
+				    bioc->num_stripes - 1 : bioc->num_stripes - 2;
+		int i;
+
+		/* This special write only works for data stripes. */
+		ASSERT(mirror_num == 1);
+		for (i = 0; i < data_stripes; i++) {
+			u64 stripe_start = bioc->full_stripe_logical +
+					   (i << BTRFS_STRIPE_LEN_SHIFT);
+
+			if (logical >= stripe_start &&
+			    logical < stripe_start + BTRFS_STRIPE_LEN)
+				break;
+		}
+		ASSERT(i < data_stripes);
+		smap.dev = bioc->stripes[i].dev;
+		smap.physical = bioc->stripes[i].physical +
+				((logical - bioc->full_stripe_logical) &
+				 BTRFS_STRIPE_LEN_MASK);
+		goto submit;
+	}
+	ASSERT(mirror_num <= bioc->num_stripes);
+	smap.dev = bioc->stripes[mirror_num - 1].dev;
+	smap.physical = bioc->stripes[mirror_num - 1].physical;
+submit:
+	ASSERT(smap.dev);
+	btrfs_put_bioc(bioc);
+	bioc = NULL;
+	if (dev_replace) {
+		ASSERT(smap.dev == fs_info->dev_replace.srcdev);
+		smap.dev = fs_info->dev_replace.tgtdev;
+	}
+	__btrfs_submit_bio(&bbio->bio, bioc, &smap, mirror_num);
+	return;
+
+fail:
+	btrfs_bio_counter_dec(fs_info);
+	btrfs_bio_end_io(bbio, errno_to_blk_status(ret));
+}
+
 void btrfs_submit_bio(struct btrfs_bio *bbio, int mirror_num)
 {
 	while (!btrfs_submit_chunk(bbio, mirror_num))
diff --git a/fs/btrfs/bio.h b/fs/btrfs/bio.h
index afbcf318fdda..ad5a6a558662 100644
--- a/fs/btrfs/bio.h
+++ b/fs/btrfs/bio.h
@@ -107,6 +107,8 @@ static inline void btrfs_bio_end_io(struct btrfs_bio *bbio, blk_status_t status)
 
 void btrfs_submit_bio(struct btrfs_bio *bbio, int mirror_num);
 void btrfs_submit_scrub_read(struct btrfs_bio *bbio, int mirror_num);
+void btrfs_submit_scrub_write(struct btrfs_bio *bbio, int mirror_num,
+			      bool dev_replace);
 int btrfs_repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
 			    u64 length, u64 logical, struct page *page,
 			    unsigned int pg_offset, int mirror_num);
-- 
2.39.2

Re: [PATCH v4 04/13] btrfs: introduce a new helper to submit write bio for scrub

[Christoph Hellwig]

On Sun, Mar 26, 2023 at 07:06:33PM +0800, Qu Wenruo wrote:
> +	/* Caller should ensure the @bbio doesn't cross stripe boundary. */
> +	ASSERT(map_length >= length);
> +	if (btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE && btrfs_is_zoned(fs_info)) {
> +		bbio->bio.bi_opf &= ~REQ_OP_WRITE;
> +		bbio->bio.bi_opf |= REQ_OP_ZONE_APPEND;
> +	}

Not crossing the stripe boundary is not enough, for zone append it
also must not cross the zone append limit, which (at least in theory)
can be arbitrarily small.

> +	if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
> +		int data_stripes = (bioc->map_type & BTRFS_BLOCK_GROUP_RAID5) ?
> +				    bioc->num_stripes - 1 : bioc->num_stripes - 2;

This calculation feels like it should be in a well document simple
helper.

> +		smap.physical = bioc->stripes[i].physical +
> +				((logical - bioc->full_stripe_logical) &
> +				 BTRFS_STRIPE_LEN_MASK);

This calculation feels like another candidate for a self contained
a well documented helper.


> +		goto submit;
> +	}
> +	ASSERT(mirror_num <= bioc->num_stripes);
> +	smap.dev = bioc->stripes[mirror_num - 1].dev;
> +	smap.physical = bioc->stripes[mirror_num - 1].physical;
> +submit:

Why no else instead of the goto here?  That would read a lot easier.

Re: [PATCH v4 04/13] btrfs: introduce a new helper to submit write bio for scrub

[Qu Wenruo]

On 2023/3/27 11:44, Christoph Hellwig wrote:
> On Sun, Mar 26, 2023 at 07:06:33PM +0800, Qu Wenruo wrote:
>> +	/* Caller should ensure the @bbio doesn't cross stripe boundary. */
>> +	ASSERT(map_length >= length);
>> +	if (btrfs_op(&bbio->bio) == BTRFS_MAP_WRITE && btrfs_is_zoned(fs_info)) {
>> +		bbio->bio.bi_opf &= ~REQ_OP_WRITE;
>> +		bbio->bio.bi_opf |= REQ_OP_ZONE_APPEND;
>> +	}
> 
> Not crossing the stripe boundary is not enough, for zone append it
> also must not cross the zone append limit, which (at least in theory)
> can be arbitrarily small.

Do you mean that we can have some real zone append limit which is even 
smaller than 64K?

If so, then the write helper can be more complex than I thought...

Thanks,
Qu

> 
>> +	if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
>> +		int data_stripes = (bioc->map_type & BTRFS_BLOCK_GROUP_RAID5) ?
>> +				    bioc->num_stripes - 1 : bioc->num_stripes - 2;
> 
> This calculation feels like it should be in a well document simple
> helper.
> 
>> +		smap.physical = bioc->stripes[i].physical +
>> +				((logical - bioc->full_stripe_logical) &
>> +				 BTRFS_STRIPE_LEN_MASK);
> 
> This calculation feels like another candidate for a self contained
> a well documented helper.
> 
> 
>> +		goto submit;
>> +	}
>> +	ASSERT(mirror_num <= bioc->num_stripes);
>> +	smap.dev = bioc->stripes[mirror_num - 1].dev;
>> +	smap.physical = bioc->stripes[mirror_num - 1].physical;
>> +submit:
> 
> Why no else instead of the goto here?  That would read a lot easier.

Re: [PATCH v4 04/13] btrfs: introduce a new helper to submit write bio for scrub

[Christoph Hellwig]

On Mon, Mar 27, 2023 at 12:32:22PM +0800, Qu Wenruo wrote:
> > Not crossing the stripe boundary is not enough, for zone append it
> > also must not cross the zone append limit, which (at least in theory)
> > can be arbitrarily small.
> 
> Do you mean that we can have some real zone append limit which is even
> smaller than 64K?
> 
> If so, then the write helper can be more complex than I thought...

In theory it can be as small as a single LBA.  It might make sense
to require a minimum of 64k for btrfs, and reject the writable mount
if it is not, as a device with just a 64k zone append limit or smaller
would be really horrible to use anyway.

Re: [PATCH v4 04/13] btrfs: introduce a new helper to submit write bio for scrub

[Qu Wenruo]

On 2023/3/27 13:22, Christoph Hellwig wrote:
> On Mon, Mar 27, 2023 at 12:32:22PM +0800, Qu Wenruo wrote:
>>> Not crossing the stripe boundary is not enough, for zone append it
>>> also must not cross the zone append limit, which (at least in theory)
>>> can be arbitrarily small.
>>
>> Do you mean that we can have some real zone append limit which is even
>> smaller than 64K?
>>
>> If so, then the write helper can be more complex than I thought...
> 
> In theory it can be as small as a single LBA.  It might make sense
> to require a minimum of 64k for btrfs, and reject the writable mount
> if it is not, as a device with just a 64k zone append limit or smaller
> would be really horrible to use anyway.

The rejection method sounds very reasonable to me.

Although I'd prefer some feedback from Johannes on the real world 
values, and if possible let the zoned guys submit the patch.

I haven't yet build my VMs to run ZNS tests.

Another thing is, if we want to implement the rejection before the 
reworked scrub, the threshold would be 128K, as that's the bio size 
limit for the old scrub code.

Thanks,
Qu

Re: [PATCH v4 04/13] btrfs: introduce a new helper to submit write bio for scrub

[Johannes Thumshirn]

On 27.03.23 09:52, Qu Wenruo wrote:
> 
> 
> On 2023/3/27 13:22, Christoph Hellwig wrote:
>> On Mon, Mar 27, 2023 at 12:32:22PM +0800, Qu Wenruo wrote:
>>>> Not crossing the stripe boundary is not enough, for zone append it
>>>> also must not cross the zone append limit, which (at least in theory)
>>>> can be arbitrarily small.
>>>
>>> Do you mean that we can have some real zone append limit which is even
>>> smaller than 64K?
>>>
>>> If so, then the write helper can be more complex than I thought...
>>
>> In theory it can be as small as a single LBA.  It might make sense
>> to require a minimum of 64k for btrfs, and reject the writable mount
>> if it is not, as a device with just a 64k zone append limit or smaller
>> would be really horrible to use anyway.
> 
> The rejection method sounds very reasonable to me.
> 
> Although I'd prefer some feedback from Johannes on the real world 
> values, and if possible let the zoned guys submit the patch.
> 

Sure rejecting sub 64k ZA limits sounds reasonable to me as well.
I can craft a patch if you want.

> I haven't yet build my VMs to run ZNS tests.
> 
> Another thing is, if we want to implement the rejection before the 
> reworked scrub, the threshold would be 128K, as that's the bio size 
> limit for the old scrub code.
> 
> Thanks,
> Qu
> 

[PATCH v4 05/13] btrfs: scrub: introduce the structure for new BTRFS_STRIPE_LEN based interface

[Qu Wenruo]

This patch introduces the following structures:

- scrub_sector_verification
  Contains all the needed info to verify one sector (data or metadata).

- scrub_stripe
  Contains all needed members (mostly bitmap based) to scrub one stripe
  (with a length of BTRFS_STRIPE_LEN).

The basic idea is, we keep the existing per-device scrub behavior, but
merge all the scrub_bio/scrub_bio into one generic structure, and read
the full BTRFS_STRIPE_LEN stripe in the first try.

This means we will read some sectors which is not scrub target, but
that's fine. At dev-replace time we only writeback the utilized and good
sectors, and for read-repair we only writeback the repaired sectors.

With every read submitted in BTRFS_STRIPE_LEN, the need for complex bio
formshaping would be gone.
Although to get the same performance of the old scrub behavior, we would
need to submit the initial read for two stripes at once.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 142 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/scrub.h |   8 +++
 2 files changed, 150 insertions(+)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index e765eb8b8bcf..05ecd1e5c513 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -70,6 +70,94 @@ struct scrub_ctx;
  */
 #define BTRFS_MAX_MIRRORS (4 + 1)
 
+/* Represent one sector and its needed info to verify the content. */
+struct scrub_sector_verification {
+	bool is_metadata;
+
+	union {
+		/*
+		 * Csum pointer for data csum verification.
+		 * Should point to a sector csum inside scrub_stripe::csums.
+		 *
+		 * NULL if this data sector has no csum.
+		 */
+		u8 *csum;
+
+		/*
+		 * Extra info for metadata verification.
+		 * All sectors inside a tree block shares the same
+		 * geneartion.
+		 */
+		u64 generation;
+	};
+};
+
+enum scrub_stripe_flags {
+	/* Set when @mirror_num, @dev, @physical and @logical is set. */
+	SCRUB_STRIPE_FLAG_INITIALIZED,
+
+	/* Set when the read-repair is finished. */
+	SCRUB_STRIPE_FLAG_REPAIR_DONE,
+};
+
+#define SCRUB_STRIPE_PAGES		(BTRFS_STRIPE_LEN / PAGE_SIZE)
+/*
+ * Represent one continuous range with a length of BTRFS_STRIPE_LEN.
+ */
+struct scrub_stripe {
+	struct btrfs_block_group *bg;
+
+	struct page *pages[SCRUB_STRIPE_PAGES];
+	struct scrub_sector_verification *sectors;
+
+	struct btrfs_device *dev;
+	u64 logical;
+	u64 physical;
+
+	u16 mirror_num;
+
+	/* Should be BTRFS_STRIPE_LEN / sectorsize. */
+	u16 nr_sectors;
+
+	atomic_t pending_io;
+	wait_queue_head_t io_wait;
+
+	/*
+	 * Indicates the states of the stripe.
+	 * Bits are defined in scrub_stripe_flags enum.
+	 */
+	unsigned long state;
+
+	/* Indicates which sectors are covered by extent items. */
+	unsigned long extent_sector_bitmap;
+
+	/*
+	 * The errors hit during the initial read of the stripe.
+	 *
+	 * Would be utilized for error reporting and repair.
+	 */
+	unsigned long init_error_bitmap;
+
+	/*
+	 * The following error bitmaps are all for the current status.
+	 * Every time we submit a new read, those bitmaps may be updated.
+	 *
+	 * error_bitmap = io_error_bitmap | csum_error_bitmap | meta_error_bitmap;
+	 *
+	 * IO and csum errors can happen for both metadata and data.
+	 */
+	unsigned long error_bitmap;
+	unsigned long io_error_bitmap;
+	unsigned long csum_error_bitmap;
+	unsigned long meta_error_bitmap;
+
+	/*
+	 * Checksum for the whole stripe if this stripe is inside a data block
+	 * group.
+	 */
+	u8 *csums;
+};
+
 struct scrub_recover {
 	refcount_t		refs;
 	struct btrfs_io_context	*bioc;
@@ -266,6 +354,60 @@ static void detach_scrub_page_private(struct page *page)
 #endif
 }
 
+static void release_scrub_stripe(struct scrub_stripe *stripe)
+{
+	if (!stripe)
+		return;
+
+	for (int i = 0; i < SCRUB_STRIPE_PAGES; i++) {
+		if (stripe->pages[i])
+			__free_page(stripe->pages[i]);
+		stripe->pages[i] = NULL;
+	}
+	kfree(stripe->sectors);
+	kfree(stripe->csums);
+	stripe->sectors = NULL;
+	stripe->csums = NULL;
+	stripe->state = 0;
+}
+
+int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe)
+{
+	int ret;
+
+	memset(stripe, 0, sizeof(*stripe));
+
+	stripe->nr_sectors = BTRFS_STRIPE_LEN >> fs_info->sectorsize_bits;
+	stripe->state = 0;
+
+	init_waitqueue_head(&stripe->io_wait);
+	atomic_set(&stripe->pending_io, 0);
+
+	ret = btrfs_alloc_page_array(SCRUB_STRIPE_PAGES, stripe->pages);
+	if (ret < 0)
+		goto error;
+
+	stripe->sectors = kcalloc(stripe->nr_sectors,
+				  sizeof(struct scrub_sector_verification),
+				  GFP_KERNEL);
+	if (!stripe->sectors)
+		goto error;
+
+	stripe->csums = kzalloc((BTRFS_STRIPE_LEN >> fs_info->sectorsize_bits) *
+				fs_info->csum_size, GFP_KERNEL);
+	if (!stripe->csums)
+		goto error;
+	return 0;
+error:
+	release_scrub_stripe(stripe);
+	return -ENOMEM;
+}
+
+void wait_scrub_stripe_io(struct scrub_stripe *stripe)
+{
+	wait_event(stripe->io_wait, atomic_read(&stripe->pending_io) == 0);
+}
+
 static struct scrub_block *alloc_scrub_block(struct scrub_ctx *sctx,
 					     struct btrfs_device *dev,
 					     u64 logical, u64 physical,
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index 7639103ebf9d..e04764f8bb7e 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -13,4 +13,12 @@ int btrfs_scrub_cancel_dev(struct btrfs_device *dev);
 int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
 			 struct btrfs_scrub_progress *progress);
 
+/*
+ * The following functions are temporary exports to avoid warning on unused
+ * static functions.
+ */
+struct scrub_stripe;
+int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe);
+void wait_scrub_stripe_io(struct scrub_stripe *stripe);
+
 #endif
-- 
2.39.2

[PATCH v4 06/13] btrfs: scrub: introduce a helper to find and fill the sector info for a scrub_stripe

[Qu Wenruo]

The new helper will search the extent tree to find the first extent of a
logical range, then fill the sectors array by two loops:

- Loop 1 to fill common bits and metadata generation

- Loop 2 to fill csum data (only for data bgs)
  This loop will use the new btrfs_lookup_csums_bitmap() to fill
  the full csum buffer, and set scrub_sector_verification::csum.

With all the needed info fulfilled by this function, later we only need
to submit and verify the stripe.

Here we temporarily export the helper to avoid wanring on unused static
function.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/file-item.c |   9 ++-
 fs/btrfs/file-item.h |   3 +-
 fs/btrfs/raid56.c    |   2 +-
 fs/btrfs/scrub.c     | 148 +++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/scrub.h     |   4 ++
 5 files changed, 163 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 1ce306cea690..018c711a0bc8 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -597,7 +597,8 @@ int btrfs_lookup_csums_list(struct btrfs_root *root, u64 start, u64 end,
  * in is large enough to contain all csums.
  */
 int btrfs_lookup_csums_bitmap(struct btrfs_root *root, u64 start, u64 end,
-			      u8 *csum_buf, unsigned long *csum_bitmap)
+			      u8 *csum_buf, unsigned long *csum_bitmap,
+			      bool search_commit)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct btrfs_key key;
@@ -614,6 +615,12 @@ int btrfs_lookup_csums_bitmap(struct btrfs_root *root, u64 start, u64 end,
 	if (!path)
 		return -ENOMEM;
 
+	if (search_commit) {
+		path->skip_locking = 1;
+		path->reada = READA_FORWARD;
+		path->search_commit_root = 1;
+	}
+
 	key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 	key.type = BTRFS_EXTENT_CSUM_KEY;
 	key.offset = start;
diff --git a/fs/btrfs/file-item.h b/fs/btrfs/file-item.h
index cd7f2ae515c0..6be8725cd574 100644
--- a/fs/btrfs/file-item.h
+++ b/fs/btrfs/file-item.h
@@ -57,7 +57,8 @@ int btrfs_lookup_csums_list(struct btrfs_root *root, u64 start, u64 end,
 			    struct list_head *list, int search_commit,
 			    bool nowait);
 int btrfs_lookup_csums_bitmap(struct btrfs_root *root, u64 start, u64 end,
-			      u8 *csum_buf, unsigned long *csum_bitmap);
+			      u8 *csum_buf, unsigned long *csum_bitmap,
+			      bool search_commit);
 void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
 				     const struct btrfs_path *path,
 				     struct btrfs_file_extent_item *fi,
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 6cbbaa6c06ca..a64b40000d12 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -2113,7 +2113,7 @@ static void fill_data_csums(struct btrfs_raid_bio *rbio)
 	}
 
 	ret = btrfs_lookup_csums_bitmap(csum_root, start, start + len - 1,
-					rbio->csum_buf, rbio->csum_bitmap);
+					rbio->csum_buf, rbio->csum_bitmap, false);
 	if (ret < 0)
 		goto error;
 	if (bitmap_empty(rbio->csum_bitmap, len >> fs_info->sectorsize_bits))
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 05ecd1e5c513..ed55a7363b8a 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -3642,6 +3642,154 @@ static int sync_write_pointer_for_zoned(struct scrub_ctx *sctx, u64 logical,
 	return ret;
 }
 
+static void fill_one_extent_info(struct btrfs_fs_info *fs_info,
+				 struct scrub_stripe *stripe,
+				 u64 extent_start, u64 extent_len,
+				 u64 extent_flags, u64 extent_gen)
+{
+	u64 cur_logical;
+
+	for (cur_logical = max(stripe->logical, extent_start);
+	     cur_logical < min(stripe->logical + BTRFS_STRIPE_LEN,
+			       extent_start + extent_len);
+	     cur_logical += fs_info->sectorsize) {
+		const int nr_sector = (cur_logical - stripe->logical) >>
+				      fs_info->sectorsize_bits;
+		struct scrub_sector_verification *sector =
+			&stripe->sectors[nr_sector];
+
+		set_bit(nr_sector, &stripe->extent_sector_bitmap);
+		if (extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
+			sector->is_metadata = true;
+			sector->generation = extent_gen;
+		}
+	}
+}
+
+static void scrub_stripe_reset_bitmaps(struct scrub_stripe *stripe)
+{
+	stripe->init_error_bitmap = 0;
+	stripe->error_bitmap = 0;
+	stripe->io_error_bitmap = 0;
+	stripe->csum_error_bitmap = 0;
+	stripe->meta_error_bitmap = 0;
+}
+
+/*
+ * Locate one stripe which has at least one extent in its range.
+ *
+ * Return 0 if found such stripe, and store its info into @stripe.
+ * Return >0 if there is no such stripe in the specified range.
+ * Return <0 for error.
+ */
+int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
+				 struct btrfs_device *dev, u64 physical,
+				 int mirror_num, u64 logical_start,
+				 u32 logical_len, struct scrub_stripe *stripe)
+{
+	struct btrfs_fs_info *fs_info = bg->fs_info;
+	struct btrfs_root *extent_root = btrfs_extent_root(fs_info, bg->start);
+	struct btrfs_root *csum_root = btrfs_csum_root(fs_info, bg->start);
+	const u64 logical_end = logical_start + logical_len;
+	struct btrfs_path path = { 0 };
+	u64 cur_logical = logical_start;
+	u64 stripe_end;
+	u64 extent_start;
+	u64 extent_len;
+	u64 extent_flags;
+	u64 extent_gen;
+	int ret;
+
+	memset(stripe->sectors, 0, sizeof(struct scrub_sector_verification) *
+				   stripe->nr_sectors);
+	scrub_stripe_reset_bitmaps(stripe);
+
+	/* The range must be inside the bg */
+	ASSERT(logical_start >= bg->start && logical_end <= bg->start + bg->length);
+
+	path.search_commit_root = 1;
+	path.skip_locking = 1;
+
+	ret = find_first_extent_item(extent_root, &path, logical_start,
+				     logical_len);
+	/* Either error or not found. */
+	if (ret)
+		goto out;
+	get_extent_info(&path, &extent_start, &extent_len,
+			&extent_flags, &extent_gen);
+	cur_logical = max(extent_start, cur_logical);
+
+	/*
+	 * Round down to stripe boundary.
+	 *
+	 * The extra calculation against bg->start is to handle block groups
+	 * whose logical bytenr is not BTRFS_STRIPE_LEN aligned.
+	 */
+	stripe->logical = round_down(cur_logical - bg->start, BTRFS_STRIPE_LEN) +
+			  bg->start;
+	stripe->physical = physical + stripe->logical - logical_start;
+	stripe->dev = dev;
+	stripe->bg = bg;
+	stripe->mirror_num = mirror_num;
+	stripe_end = stripe->logical + BTRFS_STRIPE_LEN - 1;
+
+	/* Fill the first extent info into stripe->sectors[] array. */
+	fill_one_extent_info(fs_info, stripe, extent_start, extent_len,
+			     extent_flags, extent_gen);
+	cur_logical = extent_start + extent_len;
+
+	/* Fill the extent info for the remaining sectors. */
+	while (cur_logical <= stripe_end) {
+		ret = find_first_extent_item(extent_root, &path, cur_logical,
+					     stripe_end - cur_logical + 1);
+		if (ret < 0)
+			goto out;
+		if (ret > 0) {
+			ret = 0;
+			break;
+		}
+		get_extent_info(&path, &extent_start, &extent_len,
+				&extent_flags, &extent_gen);
+		fill_one_extent_info(fs_info, stripe, extent_start, extent_len,
+				     extent_flags, extent_gen);
+		cur_logical = extent_start + extent_len;
+	}
+
+	/* Now fill the data csum. */
+	if (bg->flags & BTRFS_BLOCK_GROUP_DATA) {
+		int sector_nr;
+		unsigned long csum_bitmap = 0;
+
+		/* Csum space should have already been allocated. */
+		ASSERT(stripe->csums);
+
+		/*
+		 * Our csum bitmap should be large enough, as BTRFS_STRIPE_LEN
+		 * should contain at most 16 sectors.
+		 */
+		ASSERT(BITS_PER_LONG >=
+		       BTRFS_STRIPE_LEN >> fs_info->sectorsize_bits);
+
+		ret = btrfs_lookup_csums_bitmap(csum_root, stripe->logical,
+						stripe_end, stripe->csums,
+						&csum_bitmap, true);
+		if (ret < 0)
+			goto out;
+		if (ret > 0)
+			ret = 0;
+
+		for_each_set_bit(sector_nr, &csum_bitmap, stripe->nr_sectors) {
+			stripe->sectors[sector_nr].csum = stripe->csums +
+				sector_nr * fs_info->csum_size;
+		}
+	}
+	set_bit(SCRUB_STRIPE_FLAG_INITIALIZED, &stripe->state);
+out:
+	btrfs_release_path(&path);
+	return ret;
+}
+
+
 /*
  * Scrub one range which can only has simple mirror based profile.
  * (Including all range in SINGLE/DUP/RAID1/RAID1C*, and each stripe in
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index e04764f8bb7e..27019d86b539 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -20,5 +20,9 @@ int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
 struct scrub_stripe;
 int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe);
 void wait_scrub_stripe_io(struct scrub_stripe *stripe);
+int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
+				 struct btrfs_device *dev, u64 physical,
+				 int mirror_num, u64 logical_start,
+				 u32 logical_len, struct scrub_stripe *stripe);
 
 #endif
-- 
2.39.2

[PATCH v4 07/13] btrfs: scrub: introduce a helper to verify one metadata

[Qu Wenruo]

The new helper, scrub_verify_one_metadata(), is almost the same as
scrub_checksum_tree_block().

The difference is in how we grab the pages.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/scrub.h |   1 +
 2 files changed, 117 insertions(+)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index ed55a7363b8a..d386fa6c1f2f 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2159,6 +2159,122 @@ static int scrub_checksum_data(struct scrub_block *sblock)
 	return sblock->checksum_error;
 }
 
+static struct page *scrub_stripe_get_page(struct scrub_stripe *stripe,
+					  int sector_nr)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	int page_index = (sector_nr << fs_info->sectorsize_bits) >> PAGE_SHIFT;
+
+	return stripe->pages[page_index];
+}
+
+static unsigned int scrub_stripe_get_page_offset(struct scrub_stripe *stripe,
+						 int sector_nr)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+
+	return offset_in_page(sector_nr << fs_info->sectorsize_bits);
+}
+
+void scrub_verify_one_metadata(struct scrub_stripe *stripe, int sector_nr)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	const unsigned int sectors_per_tree = fs_info->nodesize >>
+					      fs_info->sectorsize_bits;
+	const u64 logical = stripe->logical + (sector_nr << fs_info->sectorsize_bits);
+	const struct page *first_page = scrub_stripe_get_page(stripe, sector_nr);
+	const unsigned int first_off = scrub_stripe_get_page_offset(stripe, sector_nr);
+	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
+	u8 on_disk_csum[BTRFS_CSUM_SIZE];
+	u8 calculated_csum[BTRFS_CSUM_SIZE];
+	struct btrfs_header *header;
+
+	/*
+	 * Here we don't have a good way to attach the pages (and subpages)
+	 * to a dummy extent buffer, thus we have to directly grab the members
+	 * from pages.
+	 */
+	header = (struct btrfs_header *)(page_address(first_page) + first_off);
+	memcpy(on_disk_csum, header->csum, fs_info->csum_size);
+
+	if (logical != btrfs_stack_header_bytenr(header)) {
+		bitmap_set(&stripe->csum_error_bitmap, sector_nr,
+			   sectors_per_tree);
+		bitmap_set(&stripe->error_bitmap, sector_nr,
+			   sectors_per_tree);
+		btrfs_warn_rl(fs_info,
+		"tree block %llu mirror %u has bad bytenr, has %llu want %llu",
+			      logical, stripe->mirror_num,
+			      btrfs_stack_header_bytenr(header), logical);
+		return;
+	}
+	if (memcmp(header->fsid, fs_info->fs_devices->fsid, BTRFS_FSID_SIZE) != 0) {
+		bitmap_set(&stripe->meta_error_bitmap, sector_nr,
+			   sectors_per_tree);
+		bitmap_set(&stripe->error_bitmap, sector_nr,
+			   sectors_per_tree);
+		btrfs_warn_rl(fs_info,
+		"tree block %llu mirror %u has bad fsid, has %pU want %pU",
+			      logical, stripe->mirror_num,
+			      header->fsid, fs_info->fs_devices->fsid);
+		return;
+	}
+	if (memcmp(header->chunk_tree_uuid, fs_info->chunk_tree_uuid,
+		   BTRFS_UUID_SIZE) != 0) {
+		bitmap_set(&stripe->meta_error_bitmap, sector_nr,
+			   sectors_per_tree);
+		bitmap_set(&stripe->error_bitmap, sector_nr,
+			   sectors_per_tree);
+		btrfs_warn_rl(fs_info,
+		"tree block %llu mirror %u has bad chunk tree uuid, has %pU want %pU",
+			      logical, stripe->mirror_num,
+			      header->chunk_tree_uuid, fs_info->chunk_tree_uuid);
+		return;
+	}
+
+	/* Now check tree block csum. */
+	shash->tfm = fs_info->csum_shash;
+	crypto_shash_init(shash);
+	crypto_shash_update(shash, page_address(first_page) + first_off +
+			    BTRFS_CSUM_SIZE, fs_info->sectorsize - BTRFS_CSUM_SIZE);
+
+	for (int i = sector_nr + 1; i < sector_nr + sectors_per_tree; i++) {
+		struct page *page = scrub_stripe_get_page(stripe, i);
+		unsigned int page_off = scrub_stripe_get_page_offset(stripe, i);
+
+		crypto_shash_update(shash, page_address(page) + page_off,
+				    fs_info->sectorsize);
+	}
+	crypto_shash_final(shash, calculated_csum);
+	if (memcmp(calculated_csum, on_disk_csum, fs_info->csum_size) != 0) {
+		bitmap_set(&stripe->meta_error_bitmap, sector_nr,
+			   sectors_per_tree);
+		bitmap_set(&stripe->error_bitmap, sector_nr,
+			   sectors_per_tree);
+		btrfs_warn_rl(fs_info,
+		"tree block %llu mirror %u has bad csum, has " CSUM_FMT " want " CSUM_FMT,
+			      logical, stripe->mirror_num,
+			      CSUM_FMT_VALUE(fs_info->csum_size, on_disk_csum),
+			      CSUM_FMT_VALUE(fs_info->csum_size, calculated_csum));
+		return;
+	}
+	if (stripe->sectors[sector_nr].generation !=
+	    btrfs_stack_header_generation(header)) {
+		bitmap_set(&stripe->meta_error_bitmap, sector_nr,
+			   sectors_per_tree);
+		bitmap_set(&stripe->error_bitmap, sector_nr,
+			   sectors_per_tree);
+		btrfs_warn_rl(fs_info,
+		"tree block %llu mirror %u has bad geneartion, has %llu want %llu",
+			      logical, stripe->mirror_num,
+			      btrfs_stack_header_generation(header),
+			      stripe->sectors[sector_nr].generation);
+	}
+	bitmap_clear(&stripe->error_bitmap, sector_nr, sectors_per_tree);
+	bitmap_clear(&stripe->csum_error_bitmap, sector_nr, sectors_per_tree);
+	bitmap_clear(&stripe->meta_error_bitmap, sector_nr, sectors_per_tree);
+}
+
 static int scrub_checksum_tree_block(struct scrub_block *sblock)
 {
 	struct scrub_ctx *sctx = sblock->sctx;
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index 27019d86b539..0d8bdc7df89c 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -24,5 +24,6 @@ int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
 				 struct btrfs_device *dev, u64 physical,
 				 int mirror_num, u64 logical_start,
 				 u32 logical_len, struct scrub_stripe *stripe);
+void scrub_verify_one_metadata(struct scrub_stripe *stripe, int sector_nr);
 
 #endif
-- 
2.39.2

[PATCH v4 08/13] btrfs: scrub: introduce a helper to verify one scrub_stripe

[Qu Wenruo]

The new helper, scrub_verify_stripe(), shares the same main workflow of
the old scrub code.

The major differences are:

- How pages/page_offset is grabbed
  Everything can be grabbed from scrub_stripe easily.

- When error report happens
  Currently the helper only verify the sectors, not really doing any
  error reporting.
  The error reporting would be done after we have done the repair.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++-
 fs/btrfs/scrub.h |  2 +-
 2 files changed, 80 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index d386fa6c1f2f..001972d9a3c4 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2176,7 +2176,7 @@ static unsigned int scrub_stripe_get_page_offset(struct scrub_stripe *stripe,
 	return offset_in_page(sector_nr << fs_info->sectorsize_bits);
 }
 
-void scrub_verify_one_metadata(struct scrub_stripe *stripe, int sector_nr)
+static void scrub_verify_one_metadata(struct scrub_stripe *stripe, int sector_nr)
 {
 	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
 	const unsigned int sectors_per_tree = fs_info->nodesize >>
@@ -2275,6 +2275,84 @@ void scrub_verify_one_metadata(struct scrub_stripe *stripe, int sector_nr)
 	bitmap_clear(&stripe->meta_error_bitmap, sector_nr, sectors_per_tree);
 }
 
+static void scrub_verify_one_sector(struct scrub_stripe *stripe,
+				    int sector_nr)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	struct scrub_sector_verification *sector = &stripe->sectors[sector_nr];
+	const unsigned int sectors_per_tree = fs_info->nodesize >>
+					      fs_info->sectorsize_bits;
+	struct page *page = scrub_stripe_get_page(stripe, sector_nr);
+	unsigned int pgoff = scrub_stripe_get_page_offset(stripe, sector_nr);
+	u8 csum_buf[BTRFS_CSUM_SIZE];
+	int ret;
+
+	ASSERT(sector_nr >= 0 && sector_nr < stripe->nr_sectors);
+
+	/* Sector not utilized, skip it. */
+	if (!test_bit(sector_nr, &stripe->extent_sector_bitmap))
+		return;
+
+	/* IO error, no need to check. */
+	if (test_bit(sector_nr, &stripe->io_error_bitmap))
+		return;
+
+	/* Metadata, verify the full tree block. */
+	if (sector->is_metadata) {
+		/*
+		 * Check if the tree block crosses the stripe boudary.
+		 * If crossed the boundary, we can not verify it but only
+		 * gives a warning.
+		 *
+		 * This can only happen in very old fs where chunks are not
+		 * ensured to be stripe aligned.
+		 */
+		if (unlikely(sector_nr + sectors_per_tree > stripe->nr_sectors)) {
+			btrfs_warn_rl(fs_info,
+			"tree block at %llu crosses stripe boundary %llu",
+				      stripe->logical +
+				      (sector_nr << fs_info->sectorsize_bits),
+				      stripe->logical);
+			return;
+		}
+		scrub_verify_one_metadata(stripe, sector_nr);
+		return;
+	}
+
+	/*
+	 * Data is much easier, we just verify the data csum (if we have).
+	 * For cases without csum, we have no other choice but to trust it.
+	 */
+	if (!sector->csum) {
+		clear_bit(sector_nr, &stripe->error_bitmap);
+		return;
+	}
+
+	ret = btrfs_check_sector_csum(fs_info, page, pgoff, csum_buf, sector->csum);
+	if (ret < 0) {
+		set_bit(sector_nr, &stripe->csum_error_bitmap);
+		set_bit(sector_nr, &stripe->error_bitmap);
+	} else {
+		clear_bit(sector_nr, &stripe->csum_error_bitmap);
+		clear_bit(sector_nr, &stripe->error_bitmap);
+	}
+}
+
+/* Verify specified sectors of a stripe. */
+void scrub_verify_one_stripe(struct scrub_stripe *stripe, unsigned long bitmap)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	const unsigned int sectors_per_tree = fs_info->nodesize >>
+					      fs_info->sectorsize_bits;
+	int sector_nr;
+
+	for_each_set_bit(sector_nr, &bitmap, stripe->nr_sectors) {
+		scrub_verify_one_sector(stripe, sector_nr);
+		if (stripe->sectors[sector_nr].is_metadata)
+			sector_nr += sectors_per_tree - 1;
+	}
+}
+
 static int scrub_checksum_tree_block(struct scrub_block *sblock)
 {
 	struct scrub_ctx *sctx = sblock->sctx;
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index 0d8bdc7df89c..45ff7e149806 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -24,6 +24,6 @@ int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
 				 struct btrfs_device *dev, u64 physical,
 				 int mirror_num, u64 logical_start,
 				 u32 logical_len, struct scrub_stripe *stripe);
-void scrub_verify_one_metadata(struct scrub_stripe *stripe, int sector_nr);
+void scrub_verify_one_stripe(struct scrub_stripe *stripe, unsigned long bitmap);
 
 #endif
-- 
2.39.2

[PATCH v4 09/13] btrfs: scrub: introduce the main read repair worker for scrub_stripe

[Qu Wenruo]

The new helper, scrub_stripe_read_repair_worker(), would handle the
read-repair part:

- Wait for the previous submitted read IO to finish

- Verify the contents of the stripe

- Go through the remaining mirrors, using as large blocksize as possible
  At this stage, we just read out all the failed sectors from each
  mirror and re-verify.
  If no more failed sector, we can exit.

- Go through all mirrors again, sector-by-sector this time
  This time, we read sector by sector, this is to address cases where
  one bad sector mismatches the drive's internal checksum, and cause the
  whole read range to fail.

  We put this recovery method as the last resort, as sector-by-sector
  reading is slow, and read from other mirrors may have already fixed
  the errors.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 210 ++++++++++++++++++++++++++++++++++++++++++++++-
 fs/btrfs/scrub.h |   3 +-
 2 files changed, 209 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 001972d9a3c4..0effda7bd1a8 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -121,6 +121,7 @@ struct scrub_stripe {
 
 	atomic_t pending_io;
 	wait_queue_head_t io_wait;
+	wait_queue_head_t repair_wait;
 
 	/*
 	 * Indicates the states of the stripe.
@@ -156,6 +157,8 @@ struct scrub_stripe {
 	 * group.
 	 */
 	u8 *csums;
+
+	struct work_struct work;
 };
 
 struct scrub_recover {
@@ -381,6 +384,7 @@ int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe
 	stripe->state = 0;
 
 	init_waitqueue_head(&stripe->io_wait);
+	init_waitqueue_head(&stripe->repair_wait);
 	atomic_set(&stripe->pending_io, 0);
 
 	ret = btrfs_alloc_page_array(SCRUB_STRIPE_PAGES, stripe->pages);
@@ -403,7 +407,7 @@ int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe
 	return -ENOMEM;
 }
 
-void wait_scrub_stripe_io(struct scrub_stripe *stripe)
+static void wait_scrub_stripe_io(struct scrub_stripe *stripe)
 {
 	wait_event(stripe->io_wait, atomic_read(&stripe->pending_io) == 0);
 }
@@ -2339,7 +2343,8 @@ static void scrub_verify_one_sector(struct scrub_stripe *stripe,
 }
 
 /* Verify specified sectors of a stripe. */
-void scrub_verify_one_stripe(struct scrub_stripe *stripe, unsigned long bitmap)
+static void scrub_verify_one_stripe(struct scrub_stripe *stripe,
+				    unsigned long bitmap)
 {
 	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
 	const unsigned int sectors_per_tree = fs_info->nodesize >>
@@ -2353,6 +2358,207 @@ void scrub_verify_one_stripe(struct scrub_stripe *stripe, unsigned long bitmap)
 	}
 }
 
+static int calc_sector_number(struct scrub_stripe *stripe,
+			      struct bio_vec *first_bvec)
+{
+	int i;
+
+	for (i = 0; i < stripe->nr_sectors; i++) {
+		if (scrub_stripe_get_page(stripe, i) == first_bvec->bv_page &&
+		    scrub_stripe_get_page_offset(stripe, i) == first_bvec->bv_offset)
+			break;
+	}
+	ASSERT(i < stripe->nr_sectors);
+	return i;
+}
+
+/*
+ * Repair read is different to the regular read by:
+ *
+ * - Only reads the failed sectors
+ * - May have extra blocksize limits
+ */
+static void scrub_repair_read_endio(struct btrfs_bio *bbio)
+{
+	struct scrub_stripe *stripe = bbio->private;
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	struct bio_vec *bvec;
+	int sector_nr = calc_sector_number(stripe,
+					   bio_first_bvec_all(&bbio->bio));
+	int bio_size = 0;
+	int i;
+
+	ASSERT(sector_nr < stripe->nr_sectors);
+
+	bio_for_each_bvec_all(bvec, &bbio->bio, i)
+		bio_size += bvec->bv_len;
+
+	if (bbio->bio.bi_status) {
+		bitmap_set(&stripe->io_error_bitmap, sector_nr,
+			   bio_size >> fs_info->sectorsize_bits);
+		bitmap_set(&stripe->error_bitmap, sector_nr,
+			   bio_size >> fs_info->sectorsize_bits);
+	} else {
+		bitmap_clear(&stripe->io_error_bitmap, sector_nr,
+			     bio_size >> fs_info->sectorsize_bits);
+	}
+	bio_put(&bbio->bio);
+	if (atomic_dec_and_test(&stripe->pending_io))
+		wake_up(&stripe->io_wait);
+}
+
+static int calc_next_mirror(int mirror, int num_copies)
+{
+	ASSERT(mirror <= num_copies);
+	return (mirror + 1 > num_copies) ? 1 : mirror + 1;
+}
+
+static void scrub_stripe_submit_repair_read(struct scrub_stripe *stripe,
+					    int mirror, int blocksize,
+					    bool wait)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	struct btrfs_bio *bbio = NULL;
+	const unsigned long old_error_bitmap = stripe->error_bitmap;
+	int i;
+
+	ASSERT(stripe->mirror_num >= 1);
+	ASSERT(atomic_read(&stripe->pending_io) == 0);
+
+	for_each_set_bit(i, &old_error_bitmap, stripe->nr_sectors) {
+		struct page *page;
+		int pgoff;
+		int ret;
+
+		page = scrub_stripe_get_page(stripe, i);
+		pgoff = scrub_stripe_get_page_offset(stripe, i);
+
+		/* The current sector can not be merged, submit the bio. */
+		if (bbio && ((i > 0 && !test_bit(i - 1, &stripe->error_bitmap)) ||
+			     bbio->bio.bi_iter.bi_size >= blocksize)) {
+			ASSERT(bbio->bio.bi_iter.bi_size);
+			atomic_inc(&stripe->pending_io);
+			btrfs_submit_scrub_read(bbio, mirror);
+			if (wait)
+				wait_scrub_stripe_io(stripe);
+			bbio = NULL;
+		}
+
+		if (!bbio) {
+			bbio = btrfs_scrub_bio_alloc(REQ_OP_READ, fs_info,
+					scrub_repair_read_endio, stripe);
+			bbio->bio.bi_iter.bi_sector = (stripe->logical +
+				(i << fs_info->sectorsize_bits)) >> SECTOR_SHIFT;
+		}
+
+		ret = bio_add_page(&bbio->bio, page, fs_info->sectorsize, pgoff);
+		ASSERT(ret == fs_info->sectorsize);
+	}
+	if (bbio) {
+		ASSERT(bbio->bio.bi_iter.bi_size);
+		atomic_inc(&stripe->pending_io);
+		btrfs_submit_scrub_read(bbio, mirror);
+		if (wait)
+			wait_scrub_stripe_io(stripe);
+	}
+}
+
+/*
+ * The main entrance for all read related scrub work, including:
+ *
+ * - Wait for the initial read to finish
+ * - Verify and locate any bad sectors
+ * - Go through the remaining mirrors and try to read as large blocksize as
+ *   possible
+ *
+ * - Go through all mirrors (including the failed mirror) sector-by-sector
+ *
+ * Writeback does not happen here, they need extra synchronization.
+ */
+static void scrub_stripe_read_repair_worker(struct work_struct *work)
+{
+	struct scrub_stripe *stripe = container_of(work, struct scrub_stripe,
+						   work);
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	int num_copies = btrfs_num_copies(fs_info, stripe->bg->start,
+					  stripe->bg->length);
+	int mirror;
+	int i;
+
+	ASSERT(stripe->mirror_num > 0);
+
+	wait_scrub_stripe_io(stripe);
+	scrub_verify_one_stripe(stripe, stripe->extent_sector_bitmap);
+	/* Save the initial failed bitmap for later repair and report usage. */
+	stripe->init_error_bitmap = stripe->error_bitmap;
+
+	if (bitmap_empty(&stripe->init_error_bitmap, stripe->nr_sectors))
+		goto out;
+
+	/*
+	 * Try all remaining mirrors.
+	 *
+	 * Here we still try read as large block as possible, as this is faster
+	 * and we have extra safe nets to rely on.
+	 */
+	for (mirror = calc_next_mirror(stripe->mirror_num, num_copies);
+	     mirror != stripe->mirror_num;
+	     mirror = calc_next_mirror(mirror, num_copies)) {
+		const unsigned long old_error_bitmap = stripe->error_bitmap;
+
+		scrub_stripe_submit_repair_read(stripe, mirror,
+						BTRFS_STRIPE_LEN, false);
+		wait_scrub_stripe_io(stripe);
+		scrub_verify_one_stripe(stripe, old_error_bitmap);
+		if (bitmap_empty(&stripe->error_bitmap, stripe->nr_sectors))
+			goto out;
+	}
+
+	/*
+	 * Last safenet, try re-check all mirrors, including the failed one,
+	 * sector-by-sector.
+	 *
+	 * As if one sector failed the drive's internal csum, the whole read
+	 * containing the offending sector would be marked error.
+	 * Thus here we do sector-by-sector read.
+	 *
+	 * This can be slow, thus we only try it as the last resort.
+	 */
+
+	for (i = 0, mirror = stripe->mirror_num; i < num_copies;
+	     i++, mirror = calc_next_mirror(mirror, num_copies)) {
+		const unsigned long old_error_bitmap = stripe->error_bitmap;
+
+		scrub_stripe_submit_repair_read(stripe, mirror,
+						fs_info->sectorsize, true);
+		wait_scrub_stripe_io(stripe);
+		scrub_verify_one_stripe(stripe, old_error_bitmap);
+		if (bitmap_empty(&stripe->error_bitmap, stripe->nr_sectors))
+			goto out;
+	}
+out:
+	set_bit(SCRUB_STRIPE_FLAG_REPAIR_DONE, &stripe->state);
+	wake_up(&stripe->repair_wait);
+}
+
+void scrub_read_endio(struct btrfs_bio *bbio)
+{
+	struct scrub_stripe *stripe = bbio->private;
+
+	if (bbio->bio.bi_status) {
+		bitmap_set(&stripe->io_error_bitmap, 0, stripe->nr_sectors);
+		bitmap_set(&stripe->error_bitmap, 0, stripe->nr_sectors);
+	} else {
+		bitmap_clear(&stripe->io_error_bitmap, 0, stripe->nr_sectors);
+	}
+	bio_put(&bbio->bio);
+	if (atomic_dec_and_test(&stripe->pending_io)) {
+		wake_up(&stripe->io_wait);
+		INIT_WORK(&stripe->work, scrub_stripe_read_repair_worker);
+		queue_work(stripe->bg->fs_info->scrub_workers, &stripe->work);
+	}
+}
+
 static int scrub_checksum_tree_block(struct scrub_block *sblock)
 {
 	struct scrub_ctx *sctx = sblock->sctx;
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index 45ff7e149806..bcc9d398fe07 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -19,11 +19,10 @@ int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
  */
 struct scrub_stripe;
 int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe);
-void wait_scrub_stripe_io(struct scrub_stripe *stripe);
 int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
 				 struct btrfs_device *dev, u64 physical,
 				 int mirror_num, u64 logical_start,
 				 u32 logical_len, struct scrub_stripe *stripe);
-void scrub_verify_one_stripe(struct scrub_stripe *stripe, unsigned long bitmap);
+void scrub_read_endio(struct btrfs_bio *bbio);
 
 #endif
-- 
2.39.2

[PATCH v4 10/13] btrfs: scrub: introduce a writeback helper for scrub_stripe

[Qu Wenruo]

Add a new helper, scrub_write_sectors(), to submit write bios for
specified sectors to the target disk

There are several differences compared to read path:

- Utilize btrfs_submit_scrub_write()
  Now we still rely on the @mirror_num based writeback, but the
  requirement is also a little different than regular writeback
  or read, thus we have to call btrfs_submit_scrub_write().

- We can not write the full stripe back
  We can only write the sectors we have.
  There will be two call sites later, one for repaired sectors,
  one for all utilized sectors of dev-replace.

  Thus the callers should specify their own write_bitmap.

This function only submit the bios, will not wait for them unless for
zoned case.

Caller must explicitly wait for the IO to finish.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/scrub.h |  3 ++
 2 files changed, 98 insertions(+)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 0effda7bd1a8..7283b111c471 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -152,6 +152,12 @@ struct scrub_stripe {
 	unsigned long csum_error_bitmap;
 	unsigned long meta_error_bitmap;
 
+	/* For writeback (repair or replace) error report. */
+	unsigned long write_error_bitmap;
+
+	/* Writeback can be concurrent, thus we need to protect the bitmap. */
+	spinlock_t write_error_lock;
+
 	/*
 	 * Checksum for the whole stripe if this stripe is inside a data block
 	 * group.
@@ -386,6 +392,7 @@ int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe
 	init_waitqueue_head(&stripe->io_wait);
 	init_waitqueue_head(&stripe->repair_wait);
 	atomic_set(&stripe->pending_io, 0);
+	spin_lock_init(&stripe->write_error_lock);
 
 	ret = btrfs_alloc_page_array(SCRUB_STRIPE_PAGES, stripe->pages);
 	if (ret < 0)
@@ -2559,6 +2566,94 @@ void scrub_read_endio(struct btrfs_bio *bbio)
 	}
 }
 
+static void scrub_write_endio(struct btrfs_bio *bbio)
+{
+	struct scrub_stripe *stripe = bbio->private;
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	struct bio_vec *bvec;
+	unsigned long flags;
+	int sector_nr = calc_sector_number(stripe, bio_first_bvec_all(&bbio->bio));
+	unsigned int bio_size = 0;
+	int i;
+
+	bio_for_each_bvec_all(bvec, &bbio->bio, i)
+		bio_size += bvec->bv_len;
+
+	if (bbio->bio.bi_status) {
+		spin_lock_irqsave(&stripe->write_error_lock, flags);
+		bitmap_set(&stripe->write_error_bitmap, sector_nr,
+				bio_size >> fs_info->sectorsize_bits);
+		spin_unlock_irqrestore(&stripe->write_error_lock, flags);
+	}
+	bio_put(&bbio->bio);
+
+	if (atomic_dec_and_test(&stripe->pending_io))
+		wake_up(&stripe->io_wait);
+}
+
+/*
+ * Submit the write bio(s) for the sectors specified by @write_bitmap.
+ *
+ * Here we utilize btrfs_submit_scrub_write(), which has some extra benefits:
+ *
+ * - Only needs logical bytenr and mirror_num
+ *   Just like the scrub read path
+ *
+ * - Would only result writes to the specified mirror
+ *   Unlike the regular writeback path, which would write back to all stripes
+ *
+ * - Handle dev-replace and read-repair writeback differently
+ */
+void scrub_write_sectors(struct scrub_ctx *sctx,
+			struct scrub_stripe *stripe,
+			unsigned long write_bitmap, bool dev_replace)
+{
+	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
+	struct btrfs_bio *bbio = NULL;
+	bool zoned = btrfs_is_zoned(fs_info);
+	int sector_nr;
+
+	for_each_set_bit(sector_nr, &write_bitmap, stripe->nr_sectors) {
+		struct page *page = scrub_stripe_get_page(stripe, sector_nr);
+		unsigned int pgoff = scrub_stripe_get_page_offset(stripe,
+								  sector_nr);
+		int ret;
+
+		/* We should only writeback sectors covered by an extent. */
+		ASSERT(test_bit(sector_nr, &stripe->extent_sector_bitmap));
+
+		/* Can not merge with previous sector, submit the current one. */
+		if (bbio && sector_nr && !test_bit(sector_nr - 1, &write_bitmap)) {
+			fill_writer_pointer_gap(sctx, stripe->physical +
+					(sector_nr << fs_info->sectorsize_bits));
+			atomic_inc(&stripe->pending_io);
+			btrfs_submit_scrub_write(bbio, stripe->mirror_num,
+						 dev_replace);
+			/* For zoned writeback, queue depth must be 1. */
+			if (zoned)
+				wait_scrub_stripe_io(stripe);
+			bbio = NULL;
+		}
+		if (!bbio) {
+			bbio = btrfs_scrub_bio_alloc(REQ_OP_WRITE, fs_info,
+						     scrub_write_endio, stripe);
+			bbio->bio.bi_iter.bi_sector = (stripe->logical +
+				(sector_nr << fs_info->sectorsize_bits)) >>
+				SECTOR_SHIFT;
+		}
+		ret = bio_add_page(&bbio->bio, page, fs_info->sectorsize, pgoff);
+		ASSERT(ret == fs_info->sectorsize);
+	}
+	if (bbio) {
+		fill_writer_pointer_gap(sctx, bbio->bio.bi_iter.bi_sector <<
+					SECTOR_SHIFT);
+		atomic_inc(&stripe->pending_io);
+		btrfs_submit_scrub_write(bbio, stripe->mirror_num, dev_replace);
+		if (zoned)
+			wait_scrub_stripe_io(stripe);
+	}
+}
+
 static int scrub_checksum_tree_block(struct scrub_block *sblock)
 {
 	struct scrub_ctx *sctx = sblock->sctx;
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index bcc9d398fe07..3027d4c23ee8 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -24,5 +24,8 @@ int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
 				 int mirror_num, u64 logical_start,
 				 u32 logical_len, struct scrub_stripe *stripe);
 void scrub_read_endio(struct btrfs_bio *bbio);
+void scrub_write_sectors(struct scrub_ctx *sctx,
+			struct scrub_stripe *stripe,
+			unsigned long write_bitmap, bool dev_replace);
 
 #endif
-- 
2.39.2

[PATCH v4 11/13] btrfs: scrub: introduce error reporting functionality for scrub_stripe

[Qu Wenruo]

The new helper, scrub_stripe_report_errors(), will report the result of the
scrub to dmesg.

The main reporting is done by introducing a new helper,
scrub_print_common_warning(), which is mostly the same content from
scrub_print_wanring(), but without the need for a scrub_block.

Since we're reporting the errors, it's the perfect timing to update the
scrub stat too.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 167 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 158 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 7283b111c471..793c17652851 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -105,6 +105,7 @@ enum scrub_stripe_flags {
  * Represent one continuous range with a length of BTRFS_STRIPE_LEN.
  */
 struct scrub_stripe {
+	struct scrub_ctx *sctx;
 	struct btrfs_block_group *bg;
 
 	struct page *pages[SCRUB_STRIPE_PAGES];
@@ -119,6 +120,13 @@ struct scrub_stripe {
 	/* Should be BTRFS_STRIPE_LEN / sectorsize. */
 	u16 nr_sectors;
 
+	/*
+	 * How many data/meta extents are in this stripe.
+	 * Only for scrub stat report purpose.
+	 */
+	u16 nr_data_extents;
+	u16 nr_meta_extents;
+
 	atomic_t pending_io;
 	wait_queue_head_t io_wait;
 	wait_queue_head_t repair_wait;
@@ -377,6 +385,7 @@ static void release_scrub_stripe(struct scrub_stripe *stripe)
 	kfree(stripe->csums);
 	stripe->sectors = NULL;
 	stripe->csums = NULL;
+	stripe->sctx = NULL;
 	stripe->state = 0;
 }
 
@@ -1046,9 +1055,9 @@ static int scrub_print_warning_inode(u64 inum, u64 offset, u64 num_bytes,
 	return 0;
 }
 
-static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
+static void scrub_print_common_warning(const char *errstr, struct btrfs_device *dev,
+				       bool is_super, u64 logical, u64 physical)
 {
-	struct btrfs_device *dev;
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_path *path;
 	struct btrfs_key found_key;
@@ -1062,22 +1071,20 @@ static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 	u8 ref_level = 0;
 	int ret;
 
-	WARN_ON(sblock->sector_count < 1);
-	dev = sblock->dev;
-	fs_info = sblock->sctx->fs_info;
+	fs_info = dev->fs_info;
 
 	/* Super block error, no need to search extent tree. */
-	if (sblock->sectors[0]->flags & BTRFS_EXTENT_FLAG_SUPER) {
+	if (is_super) {
 		btrfs_warn_in_rcu(fs_info, "%s on device %s, physical %llu",
-			errstr, btrfs_dev_name(dev), sblock->physical);
+			errstr, btrfs_dev_name(dev), physical);
 		return;
 	}
 	path = btrfs_alloc_path();
 	if (!path)
 		return;
 
-	swarn.physical = sblock->physical;
-	swarn.logical = sblock->logical;
+	swarn.physical = physical;
+	swarn.logical = logical;
 	swarn.errstr = errstr;
 	swarn.dev = NULL;
 
@@ -1126,6 +1133,13 @@ static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 	btrfs_free_path(path);
 }
 
+static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
+{
+	scrub_print_common_warning(errstr, sblock->dev,
+			sblock->sectors[0]->flags & BTRFS_EXTENT_FLAG_SUPER,
+			sblock->logical, sblock->physical);
+}
+
 static inline void scrub_get_recover(struct scrub_recover *recover)
 {
 	refcount_inc(&recover->refs);
@@ -2470,6 +2484,132 @@ static void scrub_stripe_submit_repair_read(struct scrub_stripe *stripe,
 	}
 }
 
+static void scrub_stripe_report_errors(struct scrub_ctx *sctx,
+				       struct scrub_stripe *stripe)
+{
+	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
+	struct btrfs_fs_info *fs_info = sctx->fs_info;
+	struct btrfs_device *dev = NULL;
+	u64 physical = 0;
+	int nr_data_sectors = 0;
+	int nr_meta_sectors = 0;
+	int nr_nodatacsum_sectors = 0;
+	int nr_repaired_sectors = 0;
+	int sector_nr;
+
+	/*
+	 * Init needed infos for error reporting.
+	 *
+	 * Although our scrub_stripe infrastucture is mostly based on btrfs_submit_bio()
+	 * thus no need for dev/physical, error reporting still needs dev and physical.
+	 */
+	if (!bitmap_empty(&stripe->init_error_bitmap, stripe->nr_sectors)) {
+		u64 mapped_len = fs_info->sectorsize;
+		struct btrfs_io_context *bioc = NULL;
+		int stripe_index = stripe->mirror_num - 1;
+		int ret;
+
+		/* For scrub, our mirror_num should always start at 1. */
+		ASSERT(stripe->mirror_num >= 1);
+		ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS,
+				      stripe->logical, &mapped_len, &bioc);
+		/*
+		 * If we failed, dev will be NULL, and later detailed reports
+		 * will just be skipped.
+		 */
+		if (ret < 0)
+			goto skip;
+		physical = bioc->stripes[stripe_index].physical;
+		dev = bioc->stripes[stripe_index].dev;
+		btrfs_put_bioc(bioc);
+	}
+
+skip:
+	for_each_set_bit(sector_nr, &stripe->extent_sector_bitmap,
+			 stripe->nr_sectors) {
+		bool repaired = false;
+
+		if (stripe->sectors[sector_nr].is_metadata) {
+			nr_meta_sectors++;
+		} else {
+			nr_data_sectors++;
+			if (!stripe->sectors[sector_nr].csum)
+				nr_nodatacsum_sectors++;
+		}
+
+		if (test_bit(sector_nr, &stripe->init_error_bitmap) &&
+		    !test_bit(sector_nr, &stripe->error_bitmap)) {
+			nr_repaired_sectors++;
+			repaired = true;
+		}
+
+		/* Good sector from the beginning, nothing need to be done. */
+		if (!test_bit(sector_nr, &stripe->init_error_bitmap))
+			continue;
+
+		/*
+		 * Report error for the corrupted sectors.
+		 * If repaired, just output the message of repaired message.
+		 */
+		if (repaired) {
+			if (dev)
+				btrfs_err_rl_in_rcu(fs_info,
+			"fixed up error at logical %llu on dev %s physical %llu",
+					    stripe->logical, btrfs_dev_name(dev),
+					    physical);
+			else
+				btrfs_err_rl_in_rcu(fs_info,
+			"fixed up error at logical %llu on mirror %u",
+					    stripe->logical, stripe->mirror_num);
+			continue;
+		}
+
+		/* The remaining are all for unrepaired. */
+		if (dev)
+			btrfs_err_rl_in_rcu(fs_info,
+	"unable to fixup (regular) error at logical %llu on dev %s physical %llu",
+					    stripe->logical, btrfs_dev_name(dev),
+					    physical);
+		else
+			btrfs_err_rl_in_rcu(fs_info,
+	"unable to fixup (regular) error at logical %llu on mirror %u",
+					    stripe->logical, stripe->mirror_num);
+
+		if (test_bit(sector_nr, &stripe->io_error_bitmap))
+			if (__ratelimit(&rs) && dev)
+				scrub_print_common_warning("i/o error", dev, false,
+						     stripe->logical, physical);
+		if (test_bit(sector_nr, &stripe->csum_error_bitmap))
+			if (__ratelimit(&rs) && dev)
+				scrub_print_common_warning("checksum error", dev, false,
+						     stripe->logical, physical);
+		if (test_bit(sector_nr, &stripe->meta_error_bitmap))
+			if (__ratelimit(&rs) && dev)
+				scrub_print_common_warning("header error", dev, false,
+						     stripe->logical, physical);
+	}
+
+	spin_lock(&sctx->stat_lock);
+	sctx->stat.data_extents_scrubbed += stripe->nr_data_extents;
+	sctx->stat.tree_extents_scrubbed += stripe->nr_meta_extents;
+	sctx->stat.data_bytes_scrubbed += nr_data_sectors <<
+					  fs_info->sectorsize_bits;
+	sctx->stat.tree_bytes_scrubbed += nr_meta_sectors <<
+					  fs_info->sectorsize_bits;
+	sctx->stat.no_csum += nr_nodatacsum_sectors;
+	sctx->stat.read_errors +=
+		bitmap_weight(&stripe->io_error_bitmap, stripe->nr_sectors);
+	sctx->stat.csum_errors +=
+		bitmap_weight(&stripe->csum_error_bitmap, stripe->nr_sectors);
+	sctx->stat.verify_errors +=
+		bitmap_weight(&stripe->meta_error_bitmap, stripe->nr_sectors);
+	sctx->stat.uncorrectable_errors +=
+		bitmap_weight(&stripe->error_bitmap, stripe->nr_sectors);
+	sctx->stat.corrected_errors += nr_repaired_sectors;
+	spin_unlock(&sctx->stat_lock);
+}
+
 /*
  * The main entrance for all read related scrub work, including:
  *
@@ -2544,6 +2684,7 @@ static void scrub_stripe_read_repair_worker(struct work_struct *work)
 			goto out;
 	}
 out:
+	scrub_stripe_report_errors(stripe->sctx, stripe);
 	set_bit(SCRUB_STRIPE_FLAG_REPAIR_DONE, &stripe->state);
 	wake_up(&stripe->repair_wait);
 }
@@ -4212,6 +4353,10 @@ int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
 		goto out;
 	get_extent_info(&path, &extent_start, &extent_len,
 			&extent_flags, &extent_gen);
+	if (extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+		stripe->nr_meta_extents++;
+	if (extent_flags & BTRFS_EXTENT_FLAG_DATA)
+		stripe->nr_data_extents++;
 	cur_logical = max(extent_start, cur_logical);
 
 	/*
@@ -4245,6 +4390,10 @@ int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
 		}
 		get_extent_info(&path, &extent_start, &extent_len,
 				&extent_flags, &extent_gen);
+		if (extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+			stripe->nr_meta_extents++;
+		if (extent_flags & BTRFS_EXTENT_FLAG_DATA)
+			stripe->nr_data_extents++;
 		fill_one_extent_info(fs_info, stripe, extent_start, extent_len,
 				     extent_flags, extent_gen);
 		cur_logical = extent_start + extent_len;
-- 
2.39.2

[PATCH v4 12/13] btrfs: scrub: introduce the helper to queue a stripe for scrub

[Qu Wenruo]

The new helper, queue_scrub_stripe(), would try to queue a stripe for
scrub.
If all stripes are already in use, we will submit all the existing
stripes and wait them to finish.

Currently we would queue up to 8 stripes, to enlarge the blocksize to
512KiB to improve the performance.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 180 ++++++++++++++++++++++++++++++++++++++++++++---
 fs/btrfs/scrub.h |  13 ++--
 2 files changed, 175 insertions(+), 18 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 793c17652851..65f000354087 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -50,6 +50,7 @@ struct scrub_ctx;
  */
 #define SCRUB_SECTORS_PER_BIO	32	/* 128KiB per bio for 4KiB pages */
 #define SCRUB_BIOS_PER_SCTX	64	/* 8MiB per device in flight for 4KiB pages */
+#define SCRUB_STRIPES_PER_SCTX	8	/* That would be 8 64K stripe per-device. */
 
 /*
  * The following value times PAGE_SIZE needs to be large enough to match the
@@ -277,9 +278,11 @@ struct scrub_parity {
 
 struct scrub_ctx {
 	struct scrub_bio	*bios[SCRUB_BIOS_PER_SCTX];
+	struct scrub_stripe	stripes[SCRUB_STRIPES_PER_SCTX];
 	struct btrfs_fs_info	*fs_info;
 	int			first_free;
 	int			curr;
+	int			cur_stripe;
 	atomic_t		bios_in_flight;
 	atomic_t		workers_pending;
 	spinlock_t		list_lock;
@@ -389,7 +392,8 @@ static void release_scrub_stripe(struct scrub_stripe *stripe)
 	stripe->state = 0;
 }
 
-int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe)
+static int init_scrub_stripe(struct btrfs_fs_info *fs_info,
+			     struct scrub_stripe *stripe)
 {
 	int ret;
 
@@ -895,6 +899,9 @@ static noinline_for_stack void scrub_free_ctx(struct scrub_ctx *sctx)
 		kfree(sbio);
 	}
 
+	for (i = 0; i < SCRUB_STRIPES_PER_SCTX; i++)
+		release_scrub_stripe(&sctx->stripes[i]);
+
 	kfree(sctx->wr_curr_bio);
 	scrub_free_csums(sctx);
 	kfree(sctx);
@@ -939,6 +946,14 @@ static noinline_for_stack struct scrub_ctx *scrub_setup_ctx(
 		else
 			sctx->bios[i]->next_free = -1;
 	}
+	for (i = 0; i < SCRUB_STRIPES_PER_SCTX; i++) {
+		int ret;
+
+		ret = init_scrub_stripe(fs_info, &sctx->stripes[i]);
+		if (ret < 0)
+			goto nomem;
+		sctx->stripes[i].sctx = sctx;
+	}
 	sctx->first_free = 0;
 	atomic_set(&sctx->bios_in_flight, 0);
 	atomic_set(&sctx->workers_pending, 0);
@@ -2689,7 +2704,7 @@ static void scrub_stripe_read_repair_worker(struct work_struct *work)
 	wake_up(&stripe->repair_wait);
 }
 
-void scrub_read_endio(struct btrfs_bio *bbio)
+static void scrub_read_endio(struct btrfs_bio *bbio)
 {
 	struct scrub_stripe *stripe = bbio->private;
 
@@ -2745,9 +2760,9 @@ static void scrub_write_endio(struct btrfs_bio *bbio)
  *
  * - Handle dev-replace and read-repair writeback differently
  */
-void scrub_write_sectors(struct scrub_ctx *sctx,
-			struct scrub_stripe *stripe,
-			unsigned long write_bitmap, bool dev_replace)
+static void scrub_write_sectors(struct scrub_ctx *sctx,
+				struct scrub_stripe *stripe,
+				unsigned long write_bitmap, bool dev_replace)
 {
 	struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
 	struct btrfs_bio *bbio = NULL;
@@ -4318,10 +4333,11 @@ static void scrub_stripe_reset_bitmaps(struct scrub_stripe *stripe)
  * Return >0 if there is no such stripe in the specified range.
  * Return <0 for error.
  */
-int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
-				 struct btrfs_device *dev, u64 physical,
-				 int mirror_num, u64 logical_start,
-				 u32 logical_len, struct scrub_stripe *stripe)
+static int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
+					struct btrfs_device *dev, u64 physical,
+					int mirror_num, u64 logical_start,
+					u32 logical_len,
+					struct scrub_stripe *stripe)
 {
 	struct btrfs_fs_info *fs_info = bg->fs_info;
 	struct btrfs_root *extent_root = btrfs_extent_root(fs_info, bg->start);
@@ -4433,6 +4449,152 @@ int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
 	return ret;
 }
 
+static void scrub_reset_stripe(struct scrub_stripe *stripe)
+{
+	scrub_stripe_reset_bitmaps(stripe);
+
+	stripe->nr_meta_extents = 0;
+	stripe->nr_data_extents = 0;
+	stripe->state = 0;
+
+	for (int i = 0; i < stripe->nr_sectors; i++) {
+		stripe->sectors[i].is_metadata = false;
+		stripe->sectors[i].csum = NULL;
+		stripe->sectors[i].generation = 0;
+	}
+}
+
+static void scrub_submit_initial_read(struct scrub_ctx *sctx,
+				      struct scrub_stripe *stripe)
+{
+	struct btrfs_fs_info *fs_info = sctx->fs_info;
+	struct btrfs_bio *bbio;
+	int mirror = stripe->mirror_num;
+
+	ASSERT(stripe->bg);
+	ASSERT(stripe->mirror_num > 0);
+	ASSERT(test_bit(SCRUB_STRIPE_FLAG_INITIALIZED, &stripe->state));
+
+	bbio = btrfs_scrub_bio_alloc(REQ_OP_READ, fs_info, scrub_read_endio,
+				     stripe);
+
+	/* Read the whole stripe. */
+	bbio->bio.bi_iter.bi_sector = stripe->logical >> SECTOR_SHIFT;
+	for (int i = 0; i < BTRFS_STRIPE_LEN >> PAGE_SHIFT; i++) {
+		int ret;
+
+		ret = bio_add_page(&bbio->bio, stripe->pages[i], PAGE_SIZE, 0);
+		/* We should have allocated enough bio vectors. */
+		ASSERT(ret == PAGE_SIZE);
+	}
+	atomic_inc(&stripe->pending_io);
+
+	/*
+	 * For dev-replace, either user asks to avoid the source dev, or
+	 * the device is missing, we try the next mirror instead.
+	 */
+	if (sctx->is_dev_replace &&
+	    (fs_info->dev_replace.cont_reading_from_srcdev_mode ==
+	     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID ||
+	     !stripe->dev->bdev)) {
+		int num_copies = btrfs_num_copies(fs_info, stripe->bg->start,
+						  stripe->bg->length);
+		mirror = calc_next_mirror(mirror, num_copies);
+	}
+	btrfs_submit_scrub_read(bbio, mirror);
+}
+
+static void flush_scrub_stripes(struct scrub_ctx *sctx)
+{
+	struct btrfs_fs_info *fs_info = sctx->fs_info;
+	struct scrub_stripe *stripe;
+	const int nr_stripes = sctx->cur_stripe;
+
+	if (!nr_stripes)
+		return;
+
+	ASSERT(test_bit(SCRUB_STRIPE_FLAG_INITIALIZED, &sctx->stripes[0].state));
+	for (int i = 0; i < nr_stripes; i++) {
+		stripe = &sctx->stripes[i];
+		scrub_submit_initial_read(sctx, stripe);
+	}
+
+	for (int i = 0; i < nr_stripes; i++) {
+		stripe = &sctx->stripes[i];
+
+		wait_event(stripe->repair_wait,
+			   test_bit(SCRUB_STRIPE_FLAG_REPAIR_DONE,
+				    &stripe->state));
+	}
+
+	/*
+	 * Submit the repaired sectors.
+	 * For zoned case, we can not do repair in-place, but
+	 * queue the bg to be relocated.
+	 */
+	if (btrfs_is_zoned(fs_info)) {
+		btrfs_repair_one_zone(fs_info, sctx->stripes[0].bg->start);
+	} else {
+		for (int i = 0; i < nr_stripes; i++) {
+			unsigned long repaired;
+
+			stripe = &sctx->stripes[i];
+
+			bitmap_andnot(&repaired, &stripe->init_error_bitmap,
+				      &stripe->error_bitmap, stripe->nr_sectors);
+			scrub_write_sectors(sctx, stripe, repaired, false);
+		}
+	}
+
+	/* Submit for dev-replace. */
+	if (sctx->is_dev_replace) {
+		for (int i = 0; i < nr_stripes; i++) {
+			unsigned long good;
+
+			stripe = &sctx->stripes[i];
+
+			ASSERT(stripe->dev == fs_info->dev_replace.srcdev);
+
+			bitmap_andnot(&good, &stripe->extent_sector_bitmap,
+				      &stripe->error_bitmap, stripe->nr_sectors);
+			scrub_write_sectors(sctx, stripe, good, true);
+		}
+	}
+
+	/* Wait for above writebacks to finish. */
+	for (int i = 0; i < nr_stripes; i++) {
+		stripe = &sctx->stripes[i];
+
+		wait_scrub_stripe_io(stripe);
+		scrub_reset_stripe(stripe);
+	}
+	sctx->cur_stripe = 0;
+}
+
+int queue_scrub_stripe(struct scrub_ctx *sctx,
+		       struct btrfs_block_group *bg,
+		       struct btrfs_device *dev, int mirror_num,
+		       u64 logical, u32 length, u64 physical)
+{
+	struct scrub_stripe *stripe;
+	int ret;
+
+	/* No available slot, submit all stripes and wait for them. */
+	if (sctx->cur_stripe >= SCRUB_STRIPES_PER_SCTX)
+		flush_scrub_stripes(sctx);
+
+	stripe = &sctx->stripes[sctx->cur_stripe];
+
+	/* We can queue one stripe using the remaining slot. */
+	scrub_reset_stripe(stripe);
+	ret = scrub_find_fill_first_stripe(bg, dev, physical, mirror_num,
+					   logical, length, stripe);
+	/* Either >0 as no more extent or <0 for error. */
+	if (ret)
+		return ret;
+	sctx->cur_stripe++;
+	return 0;
+}
 
 /*
  * Scrub one range which can only has simple mirror based profile.
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index 3027d4c23ee8..fb9d906f5a17 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -18,14 +18,9 @@ int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
  * static functions.
  */
 struct scrub_stripe;
-int init_scrub_stripe(struct btrfs_fs_info *fs_info, struct scrub_stripe *stripe);
-int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
-				 struct btrfs_device *dev, u64 physical,
-				 int mirror_num, u64 logical_start,
-				 u32 logical_len, struct scrub_stripe *stripe);
-void scrub_read_endio(struct btrfs_bio *bbio);
-void scrub_write_sectors(struct scrub_ctx *sctx,
-			struct scrub_stripe *stripe,
-			unsigned long write_bitmap, bool dev_replace);
+int queue_scrub_stripe(struct scrub_ctx *sctx,
+		       struct btrfs_block_group *bg,
+		       struct btrfs_device *dev, int mirror_num,
+		       u64 logical, u32 length, u64 physical);
 
 #endif
-- 
2.39.2

[PATCH v4 13/13] btrfs: scrub: switch scrub_simple_mirror() to scrub_stripe infrastructure

[Qu Wenruo]

Switch scrub_simple_mirror() to the new scrub_stripe infrastructure.

Since scrub_simple_mirror() is the core part of scrub (only RAID56
P/Q stripes doesn't utilize it), we can get rid of a big hunk of code,
mostly scrub_extent() and scrub_sectors().

There is a functionality change:

- Scrub speed throttle now only affects read on the scrubbing device
  Writes (for repair and replace), and reads from other mirrors won't
  be limited by the limits.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 494 +++--------------------------------------------
 fs/btrfs/scrub.h |  10 -
 2 files changed, 30 insertions(+), 474 deletions(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 65f000354087..110b4c8e5847 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -582,10 +582,6 @@ static void scrub_sector_get(struct scrub_sector *sector);
 static void scrub_sector_put(struct scrub_sector *sector);
 static void scrub_parity_get(struct scrub_parity *sparity);
 static void scrub_parity_put(struct scrub_parity *sparity);
-static int scrub_sectors(struct scrub_ctx *sctx, u64 logical, u32 len,
-			 u64 physical, struct btrfs_device *dev, u64 flags,
-			 u64 gen, int mirror_num, u8 *csum,
-			 u64 physical_for_dev_replace);
 static void scrub_bio_end_io(struct bio *bio);
 static void scrub_bio_end_io_worker(struct work_struct *work);
 static void scrub_block_complete(struct scrub_block *sblock);
@@ -2975,22 +2971,16 @@ static void scrub_sector_put(struct scrub_sector *sector)
 		kfree(sector);
 }
 
-/*
- * Throttling of IO submission, bandwidth-limit based, the timeslice is 1
- * second.  Limit can be set via /sys/fs/UUID/devinfo/devid/scrub_speed_max.
- */
-static void scrub_throttle(struct scrub_ctx *sctx)
+static void scrub_throttle_dev_io(struct scrub_ctx *sctx,
+				  struct btrfs_device *device,
+				  unsigned int bio_size)
 {
 	const int time_slice = 1000;
-	struct scrub_bio *sbio;
-	struct btrfs_device *device;
 	s64 delta;
 	ktime_t now;
 	u32 div;
 	u64 bwlimit;
 
-	sbio = sctx->bios[sctx->curr];
-	device = sbio->dev;
 	bwlimit = READ_ONCE(device->scrub_speed_max);
 	if (bwlimit == 0)
 		return;
@@ -3012,7 +3002,7 @@ static void scrub_throttle(struct scrub_ctx *sctx)
 	/* Still in the time to send? */
 	if (ktime_before(now, sctx->throttle_deadline)) {
 		/* If current bio is within the limit, send it */
-		sctx->throttle_sent += sbio->bio->bi_iter.bi_size;
+		sctx->throttle_sent += bio_size;
 		if (sctx->throttle_sent <= div_u64(bwlimit, div))
 			return;
 
@@ -3034,6 +3024,17 @@ static void scrub_throttle(struct scrub_ctx *sctx)
 	sctx->throttle_deadline = 0;
 }
 
+/*
+ * Throttling of IO submission, bandwidth-limit based, the timeslice is 1
+ * second.  Limit can be set via /sys/fs/UUID/devinfo/devid/scrub_speed_max.
+ */
+static void scrub_throttle(struct scrub_ctx *sctx)
+{
+	struct scrub_bio *sbio = sctx->bios[sctx->curr];
+
+	scrub_throttle_dev_io(sctx, sbio->dev, sbio->bio->bi_iter.bi_size);
+}
+
 static void scrub_submit(struct scrub_ctx *sctx)
 {
 	struct scrub_bio *sbio;
@@ -3118,202 +3119,6 @@ static int scrub_add_sector_to_rd_bio(struct scrub_ctx *sctx,
 	return 0;
 }
 
-static void scrub_missing_raid56_end_io(struct bio *bio)
-{
-	struct scrub_block *sblock = bio->bi_private;
-	struct btrfs_fs_info *fs_info = sblock->sctx->fs_info;
-
-	btrfs_bio_counter_dec(fs_info);
-	if (bio->bi_status)
-		sblock->no_io_error_seen = 0;
-
-	bio_put(bio);
-
-	queue_work(fs_info->scrub_workers, &sblock->work);
-}
-
-static void scrub_missing_raid56_worker(struct work_struct *work)
-{
-	struct scrub_block *sblock = container_of(work, struct scrub_block, work);
-	struct scrub_ctx *sctx = sblock->sctx;
-	struct btrfs_fs_info *fs_info = sctx->fs_info;
-	u64 logical;
-	struct btrfs_device *dev;
-
-	logical = sblock->logical;
-	dev = sblock->dev;
-
-	if (sblock->no_io_error_seen)
-		scrub_recheck_block_checksum(sblock);
-
-	if (!sblock->no_io_error_seen) {
-		spin_lock(&sctx->stat_lock);
-		sctx->stat.read_errors++;
-		spin_unlock(&sctx->stat_lock);
-		btrfs_err_rl_in_rcu(fs_info,
-			"IO error rebuilding logical %llu for dev %s",
-			logical, btrfs_dev_name(dev));
-	} else if (sblock->header_error || sblock->checksum_error) {
-		spin_lock(&sctx->stat_lock);
-		sctx->stat.uncorrectable_errors++;
-		spin_unlock(&sctx->stat_lock);
-		btrfs_err_rl_in_rcu(fs_info,
-			"failed to rebuild valid logical %llu for dev %s",
-			logical, btrfs_dev_name(dev));
-	} else {
-		scrub_write_block_to_dev_replace(sblock);
-	}
-
-	if (sctx->is_dev_replace && sctx->flush_all_writes) {
-		mutex_lock(&sctx->wr_lock);
-		scrub_wr_submit(sctx);
-		mutex_unlock(&sctx->wr_lock);
-	}
-
-	scrub_block_put(sblock);
-	scrub_pending_bio_dec(sctx);
-}
-
-static void scrub_missing_raid56_pages(struct scrub_block *sblock)
-{
-	struct scrub_ctx *sctx = sblock->sctx;
-	struct btrfs_fs_info *fs_info = sctx->fs_info;
-	u64 length = sblock->sector_count << fs_info->sectorsize_bits;
-	u64 logical = sblock->logical;
-	struct btrfs_io_context *bioc = NULL;
-	struct bio *bio;
-	struct btrfs_raid_bio *rbio;
-	int ret;
-	int i;
-
-	btrfs_bio_counter_inc_blocked(fs_info);
-	ret = btrfs_map_sblock(fs_info, BTRFS_MAP_GET_READ_MIRRORS, logical,
-			       &length, &bioc);
-	if (ret || !bioc)
-		goto bioc_out;
-
-	if (WARN_ON(!sctx->is_dev_replace ||
-		    !(bioc->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK))) {
-		/*
-		 * We shouldn't be scrubbing a missing device. Even for dev
-		 * replace, we should only get here for RAID 5/6. We either
-		 * managed to mount something with no mirrors remaining or
-		 * there's a bug in scrub_find_good_copy()/btrfs_map_block().
-		 */
-		goto bioc_out;
-	}
-
-	bio = bio_alloc(NULL, BIO_MAX_VECS, REQ_OP_READ, GFP_NOFS);
-	bio->bi_iter.bi_sector = logical >> 9;
-	bio->bi_private = sblock;
-	bio->bi_end_io = scrub_missing_raid56_end_io;
-
-	rbio = raid56_alloc_missing_rbio(bio, bioc);
-	if (!rbio)
-		goto rbio_out;
-
-	for (i = 0; i < sblock->sector_count; i++) {
-		struct scrub_sector *sector = sblock->sectors[i];
-
-		raid56_add_scrub_pages(rbio, scrub_sector_get_page(sector),
-				       scrub_sector_get_page_offset(sector),
-				       sector->offset + sector->sblock->logical);
-	}
-
-	INIT_WORK(&sblock->work, scrub_missing_raid56_worker);
-	scrub_block_get(sblock);
-	scrub_pending_bio_inc(sctx);
-	raid56_submit_missing_rbio(rbio);
-	btrfs_put_bioc(bioc);
-	return;
-
-rbio_out:
-	bio_put(bio);
-bioc_out:
-	btrfs_bio_counter_dec(fs_info);
-	btrfs_put_bioc(bioc);
-	spin_lock(&sctx->stat_lock);
-	sctx->stat.malloc_errors++;
-	spin_unlock(&sctx->stat_lock);
-}
-
-static int scrub_sectors(struct scrub_ctx *sctx, u64 logical, u32 len,
-		       u64 physical, struct btrfs_device *dev, u64 flags,
-		       u64 gen, int mirror_num, u8 *csum,
-		       u64 physical_for_dev_replace)
-{
-	struct scrub_block *sblock;
-	const u32 sectorsize = sctx->fs_info->sectorsize;
-	int index;
-
-	sblock = alloc_scrub_block(sctx, dev, logical, physical,
-				   physical_for_dev_replace, mirror_num);
-	if (!sblock) {
-		spin_lock(&sctx->stat_lock);
-		sctx->stat.malloc_errors++;
-		spin_unlock(&sctx->stat_lock);
-		return -ENOMEM;
-	}
-
-	for (index = 0; len > 0; index++) {
-		struct scrub_sector *sector;
-		/*
-		 * Here we will allocate one page for one sector to scrub.
-		 * This is fine if PAGE_SIZE == sectorsize, but will cost
-		 * more memory for PAGE_SIZE > sectorsize case.
-		 */
-		u32 l = min(sectorsize, len);
-
-		sector = alloc_scrub_sector(sblock, logical);
-		if (!sector) {
-			spin_lock(&sctx->stat_lock);
-			sctx->stat.malloc_errors++;
-			spin_unlock(&sctx->stat_lock);
-			scrub_block_put(sblock);
-			return -ENOMEM;
-		}
-		sector->flags = flags;
-		sector->generation = gen;
-		if (csum) {
-			sector->have_csum = 1;
-			memcpy(sector->csum, csum, sctx->fs_info->csum_size);
-		} else {
-			sector->have_csum = 0;
-		}
-		len -= l;
-		logical += l;
-		physical += l;
-		physical_for_dev_replace += l;
-	}
-
-	WARN_ON(sblock->sector_count == 0);
-	if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state)) {
-		/*
-		 * This case should only be hit for RAID 5/6 device replace. See
-		 * the comment in scrub_missing_raid56_pages() for details.
-		 */
-		scrub_missing_raid56_pages(sblock);
-	} else {
-		for (index = 0; index < sblock->sector_count; index++) {
-			struct scrub_sector *sector = sblock->sectors[index];
-			int ret;
-
-			ret = scrub_add_sector_to_rd_bio(sctx, sector);
-			if (ret) {
-				scrub_block_put(sblock);
-				return ret;
-			}
-		}
-
-		if (flags & BTRFS_EXTENT_FLAG_SUPER)
-			scrub_submit(sctx);
-	}
-
-	/* last one frees, either here or in bio completion for last page */
-	scrub_block_put(sblock);
-	return 0;
-}
-
 static void scrub_bio_end_io(struct bio *bio)
 {
 	struct scrub_bio *sbio = bio->bi_private;
@@ -3498,179 +3303,6 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64 logical, u8 *csum)
 	return 1;
 }
 
-static bool should_use_device(struct btrfs_fs_info *fs_info,
-			      struct btrfs_device *dev,
-			      bool follow_replace_read_mode)
-{
-	struct btrfs_device *replace_srcdev = fs_info->dev_replace.srcdev;
-	struct btrfs_device *replace_tgtdev = fs_info->dev_replace.tgtdev;
-
-	if (!dev->bdev)
-		return false;
-
-	/*
-	 * We're doing scrub/replace, if it's pure scrub, no tgtdev should be
-	 * here.  If it's replace, we're going to write data to tgtdev, thus
-	 * the current data of the tgtdev is all garbage, thus we can not use
-	 * it at all.
-	 */
-	if (dev == replace_tgtdev)
-		return false;
-
-	/* No need to follow replace read mode, any existing device is fine. */
-	if (!follow_replace_read_mode)
-		return true;
-
-	/* Need to follow the mode. */
-	if (fs_info->dev_replace.cont_reading_from_srcdev_mode ==
-	    BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID)
-		return dev != replace_srcdev;
-	return true;
-}
-static int scrub_find_good_copy(struct btrfs_fs_info *fs_info,
-				u64 extent_logical, u32 extent_len,
-				u64 *extent_physical,
-				struct btrfs_device **extent_dev,
-				int *extent_mirror_num)
-{
-	u64 mapped_length;
-	struct btrfs_io_context *bioc = NULL;
-	int ret;
-	int i;
-
-	mapped_length = extent_len;
-	ret = btrfs_map_block(fs_info, BTRFS_MAP_GET_READ_MIRRORS,
-			      extent_logical, &mapped_length, &bioc, 0);
-	if (ret || !bioc || mapped_length < extent_len) {
-		btrfs_put_bioc(bioc);
-		btrfs_err_rl(fs_info, "btrfs_map_block() failed for logical %llu: %d",
-				extent_logical, ret);
-		return -EIO;
-	}
-
-	/*
-	 * First loop to exclude all missing devices and the source device if
-	 * needed.  And we don't want to use target device as mirror either, as
-	 * we're doing the replace, the target device range contains nothing.
-	 */
-	for (i = 0; i < bioc->num_stripes - bioc->replace_nr_stripes; i++) {
-		struct btrfs_io_stripe *stripe = &bioc->stripes[i];
-
-		if (!should_use_device(fs_info, stripe->dev, true))
-			continue;
-		goto found;
-	}
-	/*
-	 * We didn't find any alternative mirrors, we have to break our replace
-	 * read mode, or we can not read at all.
-	 */
-	for (i = 0; i < bioc->num_stripes - bioc->replace_nr_stripes; i++) {
-		struct btrfs_io_stripe *stripe = &bioc->stripes[i];
-
-		if (!should_use_device(fs_info, stripe->dev, false))
-			continue;
-		goto found;
-	}
-
-	btrfs_err_rl(fs_info, "failed to find any live mirror for logical %llu",
-			extent_logical);
-	return -EIO;
-
-found:
-	*extent_physical = bioc->stripes[i].physical;
-	*extent_mirror_num = i + 1;
-	*extent_dev = bioc->stripes[i].dev;
-	btrfs_put_bioc(bioc);
-	return 0;
-}
-
-static bool scrub_need_different_mirror(struct scrub_ctx *sctx,
-					struct map_lookup *map,
-					struct btrfs_device *dev)
-{
-	/*
-	 * For RAID56, all the extra mirrors are rebuilt from other P/Q,
-	 * cannot utilize other mirrors directly.
-	 */
-	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
-		return false;
-
-	if (!dev->bdev)
-		return true;
-
-	return sctx->fs_info->dev_replace.cont_reading_from_srcdev_mode ==
-		BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID;
-}
-
-/* scrub extent tries to collect up to 64 kB for each bio */
-static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
-			u64 logical, u32 len,
-			u64 physical, struct btrfs_device *dev, u64 flags,
-			u64 gen, int mirror_num)
-{
-	struct btrfs_device *src_dev = dev;
-	u64 src_physical = physical;
-	int src_mirror = mirror_num;
-	int ret;
-	u8 csum[BTRFS_CSUM_SIZE];
-	u32 blocksize;
-
-	if (flags & BTRFS_EXTENT_FLAG_DATA) {
-		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
-			blocksize = BTRFS_STRIPE_LEN;
-		else
-			blocksize = sctx->fs_info->sectorsize;
-		spin_lock(&sctx->stat_lock);
-		sctx->stat.data_extents_scrubbed++;
-		sctx->stat.data_bytes_scrubbed += len;
-		spin_unlock(&sctx->stat_lock);
-	} else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
-		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
-			blocksize = BTRFS_STRIPE_LEN;
-		else
-			blocksize = sctx->fs_info->nodesize;
-		spin_lock(&sctx->stat_lock);
-		sctx->stat.tree_extents_scrubbed++;
-		sctx->stat.tree_bytes_scrubbed += len;
-		spin_unlock(&sctx->stat_lock);
-	} else {
-		blocksize = sctx->fs_info->sectorsize;
-		WARN_ON(1);
-	}
-
-	/*
-	 * For dev-replace case, we can have @dev being a missing device, or
-	 * we want to avoid reading from the source device if possible.
-	 */
-	if (sctx->is_dev_replace && scrub_need_different_mirror(sctx, map, dev)) {
-		ret = scrub_find_good_copy(sctx->fs_info, logical, len,
-					   &src_physical, &src_dev, &src_mirror);
-		if (ret < 0)
-			return ret;
-	}
-	while (len) {
-		u32 l = min(len, blocksize);
-		int have_csum = 0;
-
-		if (flags & BTRFS_EXTENT_FLAG_DATA) {
-			/* push csums to sbio */
-			have_csum = scrub_find_csum(sctx, logical, csum);
-			if (have_csum == 0)
-				++sctx->stat.no_csum;
-		}
-		ret = scrub_sectors(sctx, logical, l, src_physical, src_dev,
-				    flags, gen, src_mirror,
-				    have_csum ? csum : NULL, physical);
-		if (ret)
-			return ret;
-		len -= l;
-		logical += l;
-		physical += l;
-		src_physical += l;
-	}
-	return 0;
-}
-
 static int scrub_sectors_for_parity(struct scrub_parity *sparity,
 				  u64 logical, u32 len,
 				  u64 physical, struct btrfs_device *dev,
@@ -4253,20 +3885,6 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
 	return ret < 0 ? ret : 0;
 }
 
-static void sync_replace_for_zoned(struct scrub_ctx *sctx)
-{
-	if (!btrfs_is_zoned(sctx->fs_info))
-		return;
-
-	sctx->flush_all_writes = true;
-	scrub_submit(sctx);
-	mutex_lock(&sctx->wr_lock);
-	scrub_wr_submit(sctx);
-	mutex_unlock(&sctx->wr_lock);
-
-	wait_event(sctx->list_wait, atomic_read(&sctx->bios_in_flight) == 0);
-}
-
 static int sync_write_pointer_for_zoned(struct scrub_ctx *sctx, u64 logical,
 					u64 physical, u64 physical_end)
 {
@@ -4514,6 +4132,9 @@ static void flush_scrub_stripes(struct scrub_ctx *sctx)
 		return;
 
 	ASSERT(test_bit(SCRUB_STRIPE_FLAG_INITIALIZED, &sctx->stripes[0].state));
+
+	scrub_throttle_dev_io(sctx, sctx->stripes[0].dev,
+			      nr_stripes << BTRFS_STRIPE_LEN_SHIFT);
 	for (int i = 0; i < nr_stripes; i++) {
 		stripe = &sctx->stripes[i];
 		scrub_submit_initial_read(sctx, stripe);
@@ -4571,10 +4192,10 @@ static void flush_scrub_stripes(struct scrub_ctx *sctx)
 	sctx->cur_stripe = 0;
 }
 
-int queue_scrub_stripe(struct scrub_ctx *sctx,
-		       struct btrfs_block_group *bg,
-		       struct btrfs_device *dev, int mirror_num,
-		       u64 logical, u32 length, u64 physical)
+static int queue_scrub_stripe(struct scrub_ctx *sctx,
+			      struct btrfs_block_group *bg,
+			      struct btrfs_device *dev, int mirror_num,
+			      u64 logical, u32 length, u64 physical)
 {
 	struct scrub_stripe *stripe;
 	int ret;
@@ -4612,11 +4233,8 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
 			       u64 physical, int mirror_num)
 {
 	struct btrfs_fs_info *fs_info = sctx->fs_info;
-	struct btrfs_root *csum_root = btrfs_csum_root(fs_info, bg->start);
-	struct btrfs_root *extent_root = btrfs_extent_root(fs_info, bg->start);
 	const u64 logical_end = logical_start + logical_length;
 	/* An artificial limit, inherit from old scrub behavior */
-	const u32 max_length = SZ_64K;
 	struct btrfs_path path = { 0 };
 	u64 cur_logical = logical_start;
 	int ret;
@@ -4628,11 +4246,7 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
 	path.skip_locking = 1;
 	/* Go through each extent items inside the logical range */
 	while (cur_logical < logical_end) {
-		u64 extent_start;
-		u64 extent_len;
-		u64 extent_flags;
-		u64 extent_gen;
-		u64 scrub_len;
+		u64 cur_physical = physical + cur_logical - logical_start;
 
 		/* Canceled? */
 		if (atomic_read(&fs_info->scrub_cancel_req) ||
@@ -4662,8 +4276,9 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
 		}
 		spin_unlock(&bg->lock);
 
-		ret = find_first_extent_item(extent_root, &path, cur_logical,
-					     logical_end - cur_logical);
+		ret = queue_scrub_stripe(sctx, bg, device, mirror_num,
+					 cur_logical, logical_end - cur_logical,
+					 cur_physical);
 		if (ret > 0) {
 			/* No more extent, just update the accounting */
 			sctx->stat.last_physical = physical + logical_length;
@@ -4672,52 +4287,11 @@ static int scrub_simple_mirror(struct scrub_ctx *sctx,
 		}
 		if (ret < 0)
 			break;
-		get_extent_info(&path, &extent_start, &extent_len,
-				&extent_flags, &extent_gen);
-		/* Skip hole range which doesn't have any extent */
-		cur_logical = max(extent_start, cur_logical);
 
-		/*
-		 * Scrub len has three limits:
-		 * - Extent size limit
-		 * - Scrub range limit
-		 *   This is especially imporatant for RAID0/RAID10 to reuse
-		 *   this function
-		 * - Max scrub size limit
-		 */
-		scrub_len = min(min(extent_start + extent_len,
-				    logical_end), cur_logical + max_length) -
-			    cur_logical;
+		ASSERT(sctx->cur_stripe > 0);
+		cur_logical = sctx->stripes[sctx->cur_stripe - 1].logical
+			      + BTRFS_STRIPE_LEN;
 
-		if (extent_flags & BTRFS_EXTENT_FLAG_DATA) {
-			ret = btrfs_lookup_csums_list(csum_root, cur_logical,
-					cur_logical + scrub_len - 1,
-					&sctx->csum_list, 1, false);
-			if (ret)
-				break;
-		}
-		if ((extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) &&
-		    does_range_cross_boundary(extent_start, extent_len,
-					      logical_start, logical_length)) {
-			btrfs_err(fs_info,
-"scrub: tree block %llu spanning boundaries, ignored. boundary=[%llu, %llu)",
-				  extent_start, logical_start, logical_end);
-			spin_lock(&sctx->stat_lock);
-			sctx->stat.uncorrectable_errors++;
-			spin_unlock(&sctx->stat_lock);
-			cur_logical += scrub_len;
-			continue;
-		}
-		ret = scrub_extent(sctx, map, cur_logical, scrub_len,
-				   cur_logical - logical_start + physical,
-				   device, extent_flags, extent_gen,
-				   mirror_num);
-		scrub_free_csums(sctx);
-		if (ret)
-			break;
-		if (sctx->is_dev_replace)
-			sync_replace_for_zoned(sctx);
-		cur_logical += scrub_len;
 		/* Don't hold CPU for too long time */
 		cond_resched();
 	}
@@ -4802,7 +4376,6 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 					   int stripe_index)
 {
 	struct btrfs_fs_info *fs_info = sctx->fs_info;
-	struct blk_plug plug;
 	struct map_lookup *map = em->map_lookup;
 	const u64 profile = map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK;
 	const u64 chunk_logical = bg->start;
@@ -4824,12 +4397,6 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 		   atomic_read(&sctx->bios_in_flight) == 0);
 	scrub_blocked_if_needed(fs_info);
 
-	/*
-	 * collect all data csums for the stripe to avoid seeking during
-	 * the scrub. This might currently (crc32) end up to be about 1MB
-	 */
-	blk_start_plug(&plug);
-
 	if (sctx->is_dev_replace &&
 	    btrfs_dev_is_sequential(sctx->wr_tgtdev, physical)) {
 		mutex_lock(&sctx->wr_lock);
@@ -4931,8 +4498,7 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 	mutex_lock(&sctx->wr_lock);
 	scrub_wr_submit(sctx);
 	mutex_unlock(&sctx->wr_lock);
-
-	blk_finish_plug(&plug);
+	flush_scrub_stripes(sctx);
 
 	if (sctx->is_dev_replace && ret >= 0) {
 		int ret2;
diff --git a/fs/btrfs/scrub.h b/fs/btrfs/scrub.h
index fb9d906f5a17..7639103ebf9d 100644
--- a/fs/btrfs/scrub.h
+++ b/fs/btrfs/scrub.h
@@ -13,14 +13,4 @@ int btrfs_scrub_cancel_dev(struct btrfs_device *dev);
 int btrfs_scrub_progress(struct btrfs_fs_info *fs_info, u64 devid,
 			 struct btrfs_scrub_progress *progress);
 
-/*
- * The following functions are temporary exports to avoid warning on unused
- * static functions.
- */
-struct scrub_stripe;
-int queue_scrub_stripe(struct scrub_ctx *sctx,
-		       struct btrfs_block_group *bg,
-		       struct btrfs_device *dev, int mirror_num,
-		       u64 logical, u32 length, u64 physical);
-
 #endif
-- 
2.39.2