linux-kernel - Re: [PATCH v2 02/11] xfs: Switch atomic write size check in xfs_file_write

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Message-ID: <20250224202456.GG21808@frogsfrogsfrogs>
Date: Mon, 24 Feb 2025 12:24:56 -0800
From: "Darrick J. Wong" <djwong@...nel.org>
To: John Garry <john.g.garry@...cle.com>
Cc: brauner@...nel.org, cem@...nel.org, dchinner@...hat.com, hch@....de,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, ojaswin@...ux.ibm.com,
	ritesh.list@...il.com, martin.petersen@...cle.com, tytso@....edu,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH v2 02/11] xfs: Switch atomic write size check in
 xfs_file_write_iter()

On Thu, Feb 13, 2025 at 01:56:10PM +0000, John Garry wrote:
> Currently the size of atomic write allowed is fixed at the blocksize.
> 
> To start to lift this restriction, refactor xfs_get_atomic_write_attr()
> to into a helper - xfs_report_atomic_write() - and use that helper to
> find the per-inode atomic write limits and check according to that.
> 
> Signed-off-by: John Garry <john.g.garry@...cle.com>

Looks fine,
Reviewed-by: "Darrick J. Wong" <djwong@...nel.org>

--D

> ---
>  fs/xfs/xfs_file.c | 12 +++++-------
>  fs/xfs/xfs_iops.c | 20 +++++++++++++++++---
>  fs/xfs/xfs_iops.h |  3 +++
>  3 files changed, 25 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index f7a7d89c345e..258c82cbce12 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -853,14 +853,12 @@ xfs_file_write_iter(
>  		return xfs_file_dax_write(iocb, from);
>  
>  	if (iocb->ki_flags & IOCB_ATOMIC) {
> -		/*
> -		 * Currently only atomic writing of a single FS block is
> -		 * supported. It would be possible to atomic write smaller than
> -		 * a FS block, but there is no requirement to support this.
> -		 * Note that iomap also does not support this yet.
> -		 */
> -		if (ocount != ip->i_mount->m_sb.sb_blocksize)
> +		unsigned int	unit_min, unit_max;
> +
> +		xfs_get_atomic_write_attr(ip, &unit_min, &unit_max);
> +		if (ocount < unit_min || ocount > unit_max)
>  			return -EINVAL;
> +
>  		ret = generic_atomic_write_valid(iocb, from);
>  		if (ret)
>  			return ret;
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 40289fe6f5b2..ea79fb246e33 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -600,15 +600,29 @@ xfs_report_dioalign(
>  		stat->dio_offset_align = stat->dio_read_offset_align;
>  }
>  
> +void
> +xfs_get_atomic_write_attr(
> +	struct xfs_inode	*ip,
> +	unsigned int		*unit_min,
> +	unsigned int		*unit_max)
> +{
> +	if (!xfs_inode_can_atomicwrite(ip)) {
> +		*unit_min = *unit_max = 0;
> +		return;
> +	}
> +
> +	*unit_min = *unit_max = ip->i_mount->m_sb.sb_blocksize;
> +}
> +
>  static void
>  xfs_report_atomic_write(
>  	struct xfs_inode	*ip,
>  	struct kstat		*stat)
>  {
> -	unsigned int		unit_min = 0, unit_max = 0;
> +	unsigned int		unit_min, unit_max;
> +
> +	xfs_get_atomic_write_attr(ip, &unit_min, &unit_max);
>  
> -	if (xfs_inode_can_atomicwrite(ip))
> -		unit_min = unit_max = ip->i_mount->m_sb.sb_blocksize;
>  	generic_fill_statx_atomic_writes(stat, unit_min, unit_max);
>  }
>  
> diff --git a/fs/xfs/xfs_iops.h b/fs/xfs/xfs_iops.h
> index 3c1a2605ffd2..ce7bdeb9a79c 100644
> --- a/fs/xfs/xfs_iops.h
> +++ b/fs/xfs/xfs_iops.h
> @@ -19,5 +19,8 @@ int xfs_inode_init_security(struct inode *inode, struct inode *dir,
>  extern void xfs_setup_inode(struct xfs_inode *ip);
>  extern void xfs_setup_iops(struct xfs_inode *ip);
>  extern void xfs_diflags_to_iflags(struct xfs_inode *ip, bool init);
> +void xfs_get_atomic_write_attr(struct xfs_inode *ip,
> +		unsigned int *unit_min, unsigned int *unit_max);
> +
>  
>  #endif /* __XFS_IOPS_H__ */
> -- 
> 2.31.1
> 
>