Replace progresses strictly from lower to higher offsets, and the
progress is tracked in chunks, by storing the physical offset of the
dev_extent which is being copied in the cursor_left field of
btrfs_dev_replace_item. When we are done copying the chunk,
left_cursor is updated to point one byte past the dev_extent, so that
on resume we can skip the dev_extents that have already been copied.
There is a major bug (which goes all the way back to the inception of
dev-replace in 3.8) in the way left_cursor is bumped: the bump is done
unconditionally, without any regard to the scrub_chunk return value.
On suspend (and also on any kind of error) scrub_chunk returns early,
i.e. without completing the copy. This leads to us skipping the chunk
that hasn't been fully copied yet when resuming.
Fix this by doing the cursor_left update only if scrub_chunk ret is 0.
(On suspend scrub_chunk returns with -ECANCELED, so this fix covers
both suspend and error cases.)
Cc: Stefan Behrens <sbehr...@giantdisaster.de>
Signed-off-by: Ilya Dryomov <idryo...@gmail.com>
---
fs/btrfs/scrub.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index a18e0e2..f21e2df 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2717,8 +2717,6 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
mutex_unlock(&fs_info->scrub_lock);
wake_up(&fs_info->scrub_pause_wait);
- dev_replace->cursor_left = dev_replace->cursor_right;
- dev_replace->item_needs_writeback = 1;
btrfs_put_block_group(cache);
if (ret)
break;
@@ -2732,6 +2730,9 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
break;
}
+ dev_replace->cursor_left = dev_replace->cursor_right;
+ dev_replace->item_needs_writeback = 1;
+
key.offset = found_key.offset + length;
btrfs_release_path(path);
}
--
1.7.10.4
--
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