Re: [PATCH 2/3] xfs: don't ever put nlink > 0 inodes on the unlinked list

Christoph Hellwig
2019-02-14T21:41:36Z

On Wed, Feb 13, 2019 at 12:50:53PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> When XFS creates an O_TMPFILE file, the inode is created with nlink = 1,
> put on the unlinked list, and then the VFS sets nlink = 0 in d_tmpfile.
> If we crash before anything logs the inode (it's dirty incore but the
> vfs doesn't tell us it's dirty so we never log that change), the iunlink
> processing part of recovery will then explode with a pile of:
>
> XFS: Assertion failed: VFS_I(ip)->i_nlink == 0, file:
> fs/xfs/xfs_log_recover.c, line: 5072
>
> Worse yet, since nlink is nonzero, the inodes also don't get cleaned up
> and they just leak until the next xfs_repair run.
>
> Therefore, change xfs_iunlink to require that inodes being put on the
> unlinked list have nlink == 0, change the tmpfile callers to instantiate
> nodes that way, and set the nlink to 1 just prior to calling d_tmpfile.
> Fix the comment for xfs_iunlink while we're at it.

Looks good for a quick fix, even if I think we should fix it different
in the long term:

Reviewed-by: Christoph Hellwig <hch@lst.de>