Re: [PATCH 6/6] xfs: port xfs_ioc_start_commit to multigrain timestamps

[Jeff Layton <jlayton@kernel.org>]

On Tue, 2024-12-03 at 19:03 -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Take advantage of the multigrain timestamp APIs to ensure that nobody
> can sneak in and write things to a file between starting a file update
> operation and committing the results.  This should have been part of the
> multigrain timestamp merge, but I forgot to fling it at jlayton when he
> resubmitted the patchset due to developer bandwidth problems.
> 
> Cc: jlayton@kernel.org
> Cc: <stable@vger.kernel.org> # v6.13-rc1
> Fixes: 4e40eff0b5737c ("fs: add infrastructure for multigrain timestamps")
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  fs/xfs/xfs_exchrange.c |   14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> 
> diff --git a/fs/xfs/xfs_exchrange.c b/fs/xfs/xfs_exchrange.c
> index 9ab05ad224d127..dd24de420714ab 100644
> --- a/fs/xfs/xfs_exchrange.c
> +++ b/fs/xfs/xfs_exchrange.c
> @@ -854,7 +854,7 @@ xfs_ioc_start_commit(
>  	struct xfs_commit_range __user	*argp)
>  {
>  	struct xfs_commit_range		args = { };
> -	struct timespec64		ts;
> +	struct kstat			kstat;
>  	struct xfs_commit_range_fresh	*kern_f;
>  	struct xfs_commit_range_fresh	__user *user_f;
>  	struct inode			*inode2 = file_inode(file);
> @@ -871,12 +871,12 @@ xfs_ioc_start_commit(
>  	memcpy(&kern_f->fsid, ip2->i_mount->m_fixedfsid, sizeof(xfs_fsid_t));
>  
>  	xfs_ilock(ip2, lockflags);
> -	ts = inode_get_ctime(inode2);
> -	kern_f->file2_ctime		= ts.tv_sec;
> -	kern_f->file2_ctime_nsec	= ts.tv_nsec;
> -	ts = inode_get_mtime(inode2);
> -	kern_f->file2_mtime		= ts.tv_sec;
> -	kern_f->file2_mtime_nsec	= ts.tv_nsec;
> +	/* Force writing of a distinct ctime if any writes happen. */
> +	fill_mg_cmtime(&kstat, STATX_CTIME | STATX_MTIME, inode2);
> +	kern_f->file2_ctime		= kstat.ctime.tv_sec;
> +	kern_f->file2_ctime_nsec	= kstat.ctime.tv_nsec;
> +	kern_f->file2_mtime		= kstat.mtime.tv_sec;
> +	kern_f->file2_mtime_nsec	= kstat.mtime.tv_nsec;
>  	kern_f->file2_ino		= ip2->i_ino;
>  	kern_f->file2_gen		= inode2->i_generation;
>  	kern_f->magic			= XCR_FRESH_MAGIC;
> 

Looks good!

Reviewed-by: Jeff Layton <jlayton@kernel.org>