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Btrfs: fix the dev-replace suspend sequence 

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 <sbehrens@giantdisaster.de>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
hifive-unleashed-5.1
Ilya Dryomov 2013-10-07 13:42:57 +03:00 committed by Chris Mason
parent 778ba82b17
commit 539f358a30
1 changed files with 3 additions and 2 deletions
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5
fs/btrfs/scrub.c
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@ -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);
}