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SubjectRe: [PATCH 4.9 083/116] btrfs: free block groups after freeing fs trees
On Thu, Feb 13, 2020 at 07:20:27AM -0800, Greg Kroah-Hartman wrote:
> From: Josef Bacik <josef@toxicpanda.com>
>
> [ Upstream commit 4e19443da1941050b346f8fc4c368aa68413bc88 ]
>
> Sometimes when running generic/475 we would trip the
> WARN_ON(cache->reserved) check when free'ing the block groups on umount.
> This is because sometimes we don't commit the transaction because of IO
> errors and thus do not cleanup the tree logs until at umount time.
>
> These blocks are still reserved until they are cleaned up, but they
> aren't cleaned up until _after_ we do the free block groups work. Fix
> this by moving the free after free'ing the fs roots, that way all of the
> tree logs are cleaned up and we have a properly cleaned fs. A bunch of
> loops of generic/475 confirmed this fixes the problem.
>
> CC: stable@vger.kernel.org # 4.9+
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> Reviewed-by: David Sterba <dsterba@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> fs/btrfs/disk-io.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index eab5a9065f093..439b5f5dc3274 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3864,6 +3864,15 @@ void close_ctree(struct btrfs_root *root)
> clear_bit(BTRFS_FS_OPEN, &fs_info->flags);
> free_root_pointers(fs_info, true);
>
> + /*
> + * We must free the block groups after dropping the fs_roots as we could
> + * have had an IO error and have left over tree log blocks that aren't
> + * cleaned up until the fs roots are freed. This makes the block group
> + * accounting appear to be wrong because there's pending reserved bytes,
> + * so make sure we do the block group cleanup afterwards.
> + */
> + btrfs_free_block_groups(fs_info);

Something's wrong here. The patch 4e19443da1 moves the
btrfs_free_block_groups() call and the stable backport lacks the "-"
line. However the patch applies cleanly on 4.9.213.

3855 btrfs_free_block_groups(fs_info);
^^^^

3856
3857 /*
3858 * we must make sure there is not any read request to
3859 * submit after we stopping all workers.
3860 */
3861 invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
3862 btrfs_stop_all_workers(fs_info);
3863
3864 clear_bit(BTRFS_FS_OPEN, &fs_info->flags);
3865 free_root_pointers(fs_info, 1);
3866
3867 /*
3868 * We must free the block groups after dropping the fs_roots as we could
3869 * have had an IO error and have left over tree log blocks that aren't
3870 * cleaned up until the fs roots are freed. This makes the block group
3871 * accounting appear to be wrong because there's pending reserved bytes,
3872 * so make sure we do the block group cleanup afterwards.
3873 */
3874 btrfs_free_block_groups(fs_info);

The first one should not be there.

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