Josef Bacik
2014-Nov-14 21:16 UTC
[PATCH] Btrfs: do not move em to modified list when unpinning
We use the modified list to keep track of which extents have been modified so we know which ones are candidates for logging at fsync() time. Newly modified extents are added to the list at modification time, around the same time the ordered extent is created. We do this so that we don't have to wait for ordered extents to complete before we know what we need to log. The problem is when something like this happens log extent 0-4k on inode 1 copy csum for 0-4k from ordered extent into log sync log commit transaction log some other extent on inode 1 ordered extent for 0-4k completes and adds itself onto modified list again log changed extents see ordered extent for 0-4k has already been logged at this point we assume the csum has been copied sync log crash On replay we will see the extent 0-4k in the log, drop the original 0-4k extent which is the same one that we are replaying which also drops the csum, and then we won't find the csum in the log for that bytenr. This of course causes us to have errors about not having csums for certain ranges of our inode. So remove the modified list manipulation in unpin_extent_cache, any modified extents should have been added well before now, and we don't want them re-logged. This fixes my test that I could reliably reproduce this problem with. Thanks, cc: stable@vger.kernel.org Signed-off-by: Josef Bacik <jbacik@fb.com> --- fs/btrfs/extent_map.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 225302b..6a98bdd 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -287,8 +287,6 @@ int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len, if (!em) goto out; - if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags)) - list_move(&em->list, &tree->modified_extents); em->generation = gen; clear_bit(EXTENT_FLAG_PINNED, &em->flags); em->mod_start = em->start; -- 1.8.3.1