On Tue, May 22, 2018 at 09:47:58AM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osan...@fb.com>
>
> Jun Wu at Facebook reported that an internal service was seeing a return
> value of 1 from ftruncate() on Btrfs in some cases.
Do you have a reproducer? To estimate how likely is to hit the problem
in practice.
> This is coming from
> the NEED_TRUNCATE_BLOCK return value from btrfs_truncate_inode_items().
>
> btrfs_truncate() uses two variables for error handling, ret and err.
> When btrfs_truncate_inode_items() returns non-zero, we set err to the
> return value. However, NEED_TRUNCATE_BLOCK is not an error. Make sure we
> only set err if ret is an error (i.e., negative).
>
> Fixes: ddfae63cc8e0 ("btrfs: move btrfs_truncate_block out of trans handle")
> Reported-by: Jun Wu <qu...@fb.com>
> Cc: sta...@vger.kernel.org
> Signed-off-by: Omar Sandoval <osan...@fb.com>
> ---
> This version makes the minimal fix which should be good for v4.17 and
> stable. I'll submit a cleanup separately.
>
> fs/btrfs/inode.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index d241285a0d2a..f276da70f659 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -9117,7 +9117,8 @@ static int btrfs_truncate(struct inode *inode, bool
> skip_writeback)
> BTRFS_EXTENT_DATA_KEY);
> trans->block_rsv = &fs_info->trans_block_rsv;
> if (ret != -ENOSPC && ret != -EAGAIN) {
> - err = ret;
> + if (ret < 0)
> + err = ret;
> break;
> }
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