btrfs: fix double __endio_write_update_ordered in direct I/O
In btrfs_submit_direct(), if we fail to allocate the btrfs_dio_private, we complete the ordered extent range. However, we don't mark that the range doesn't need to be cleaned up from btrfs_direct_IO() until later. Therefore, if we fail to allocate the btrfs_dio_private, we complete the ordered extent range twice. We could fix this by updating unsubmitted_oe_range earlier, but it's cleaner to reorganize the code so that creating the btrfs_dio_private and submitting the bios are separate, and once the btrfs_dio_private is created, cleanup always happens through the btrfs_dio_private. The logic around unsubmitted_oe_range_end and unsubmitted_oe_range_start is really subtle. We have the following: 1. btrfs_direct_IO sets those two to the same value. 2. When we call __blockdev_direct_IO unless btrfs_get_blocks_direct->btrfs_get_blocks_direct_write is called to modify unsubmitted_oe_range_start so that start < end. Cleanup won't happen. 3. We come into btrfs_submit_direct - if it dip allocation fails we'd return with oe_range_end now modified so cleanup will happen. 4. If we manage to allocate the dip we reset the unsubmitted range members to be equal so that cleanup happens from btrfs_endio_direct_write. This 4-step logic is not really obvious, especially given it's scattered across 3 functions. Fixes: f28a4928 ("Btrfs: fix leaking of ordered extents after direct IO write error") Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Omar Sandoval <osandov@fb.com> [ add range start/end logic explanation from Nikolay ] Signed-off-by: David Sterba <dsterba@suse.com>
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