diff mbox series

[2/2] btrfs: scrub: skip initial RAID stripe-tree lookup errors

Message ID 20241007115248.16434-3-jth@kernel.org (mailing list archive)
State New, archived
Headers show
Series btrfs: RST scrub fixes for prealloc | expand

Commit Message

Johannes Thumshirn Oct. 7, 2024, 11:52 a.m. UTC 
From: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Performing the initial extent sector read on a RAID stripe-tree backed
filesystem with pre-allocated extents will cause the RAID stripe-tree
lookup code to return ENODATA, as pre-allocated extents do not have any
on-disk bytes and thus no RAID stripe-tree entries.

But the current scrub read code marks these extens as errors, because the
lookup fails.

If btrfs_map_block() returns -ENODATA, it means that the call to
btrfs_get_raid_extent_offset() returned -ENODATA, because there is no
entry for the corresponding range in the RAID stripe-tree. But as this
range is in the extent-tree it means we've hit a pre-allocated extent. In
this case, don't mark the sector in the stripe's error bitmaps as faulty
and carry on to the next.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 fs/btrfs/scrub.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

David Sterba Oct. 8, 2024, 5:05 p.m. UTC | #1 
On Mon, Oct 07, 2024 at 01:52:48PM +0200, Johannes Thumshirn wrote:
> From: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> 
> Performing the initial extent sector read on a RAID stripe-tree backed
> filesystem with pre-allocated extents will cause the RAID stripe-tree
> lookup code to return ENODATA, as pre-allocated extents do not have any
> on-disk bytes and thus no RAID stripe-tree entries.
> 
> But the current scrub read code marks these extens as errors, because the
> lookup fails.
> 
> If btrfs_map_block() returns -ENODATA, it means that the call to
> btrfs_get_raid_extent_offset() returned -ENODATA, because there is no
> entry for the corresponding range in the RAID stripe-tree. But as this
> range is in the extent-tree it means we've hit a pre-allocated extent. In
> this case, don't mark the sector in the stripe's error bitmaps as faulty
> and carry on to the next.

I've added summary of this paragraph as a comment to the code, using the
ENODATA for a specific relations in the trees is quite unobvious.
diff mbox series

Patch

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index e141132b5c8d..96ac6f9e5eee 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -1704,8 +1704,10 @@  static void scrub_submit_extent_sector_read(struct scrub_ctx *sctx,
 					      &stripe_len, &bioc, &io_stripe, &mirror);
 			btrfs_put_bioc(bioc);
 			if (err < 0) {
-				set_bit(i, &stripe->io_error_bitmap);
-				set_bit(i, &stripe->error_bitmap);
+				if (err != -ENODATA) {
+					set_bit(i, &stripe->io_error_bitmap);
+					set_bit(i, &stripe->error_bitmap);
+				}
 				continue;
 			}