linux-ext4 - Re: [PATCH v5 6/8] xfs: switch to multigrain timestamps

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Date:   Wed, 19 Jul 2023 11:35:37 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Eric Van Hensbergen <ericvh@...nel.org>,
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Subject: Re: [PATCH v5 6/8] xfs: switch to multigrain timestamps

On Thu, Jul 13, 2023 at 07:00:55PM -0400, Jeff Layton wrote:
> Enable multigrain timestamps, which should ensure that there is an
> apparent change to the timestamp whenever it has been written after
> being actively observed via getattr.
> 
> Also, anytime the mtime changes, the ctime must also change, and those
> are now the only two options for xfs_trans_ichgtime. Have that function
> unconditionally bump the ctime, and warn if XFS_ICHGTIME_CHG is ever not
> set.
> 
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
> ---
>  fs/xfs/libxfs/xfs_trans_inode.c | 6 +++---
>  fs/xfs/xfs_iops.c               | 4 ++--
>  fs/xfs/xfs_super.c              | 2 +-
>  3 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_trans_inode.c b/fs/xfs/libxfs/xfs_trans_inode.c
> index 0c9df8df6d4a..86f5ffce2d89 100644
> --- a/fs/xfs/libxfs/xfs_trans_inode.c
> +++ b/fs/xfs/libxfs/xfs_trans_inode.c
> @@ -62,12 +62,12 @@ xfs_trans_ichgtime(
>  	ASSERT(tp);
>  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
>  
> -	tv = current_time(inode);
> +	/* If the mtime changes, then ctime must also change */
> +	WARN_ON_ONCE(!(flags & XFS_ICHGTIME_CHG));

Make that an ASSERT(flags & XFS_ICHGTIME_CHG), please. There's no
need to verify this at runtime on production kernels.

-Dave.
-- 
Dave Chinner
david@...morbit.com