Re: [PATCH 1/4] xfs: factor out isize updates from xfs_dio_write_end_io

[Damien Le Moal <dlemoal@kernel.org>]

On 2026/03/10 12:55, cem@kernel.org wrote:
> From: Carlos Maiolino <cem@kernel.org>
> 
> This is the only code needed for zoned inodes, so factor it out so
> we can move zoned inodes ioend to its own callback.
> 
> Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
> ---
>  fs/xfs/xfs_file.c | 59 +++++++++++++++++++++++++++++------------------
>  1 file changed, 36 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 6246f34df9fd..45ecd743fa32 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -560,6 +560,41 @@ xfs_zoned_write_space_reserve(
>  			flags, ac);
>  }
>  
> +/*
> + * We need to lock the test/set EOF update as we can be racing with
> + * other IO completions here to update the EOF. Failing to serialise
> + * here can result in EOF moving backwards and Bad Things Happen when
> + * that occurs.
> + *
> + * As IO completion only ever extends EOF, we can do an unlocked check
> + * here to avoid taking the spinlock. If we land within the current EOF,
> + * then we do not need to do an extending update at all, and we don't
> + * need to take the lock to check this. If we race with an update moving
> + * EOF, then we'll either still be beyond EOF and need to take the lock,
> + * or we'll be within EOF and we don't need to take it at all.
> + */
> +static int
> +xfs_dio_endio_set_isize(
> +	struct inode		*inode,
> +	loff_t			offset,
> +	ssize_t			size)
> +{
> +	struct xfs_inode	*ip = XFS_I(inode);
> +
> +	if (offset + size <= i_size_read(inode))
> +		return 0;
> +
> +	spin_lock(&ip->i_flags_lock);
> +	if (offset + size > i_size_read(inode)) {
> +		i_size_write(inode, offset + size);
> +		spin_unlock(&ip->i_flags_lock);
> +	} else {
> +		spin_unlock(&ip->i_flags_lock);
> +	}

The spinlock unlock does not need to be inside the if and else:

+	spin_lock(&ip->i_flags_lock);
+	if (offset + size > i_size_read(inode))
+		i_size_write(inode, offset + size);
+	spin_unlock(&ip->i_flags_lock);

Other than this, looks OK to me.

> +
> +	return xfs_setfilesize(ip, offset, size);
> +}
> +
>  static int
>  xfs_dio_write_end_io(
>  	struct kiocb		*iocb,
> @@ -623,30 +658,8 @@ xfs_dio_write_end_io(
>  	 * with the on-disk inode size being outside the in-core inode size. We
>  	 * have no other method of updating EOF for AIO, so always do it here
>  	 * if necessary.
> -	 *
> -	 * We need to lock the test/set EOF update as we can be racing with
> -	 * other IO completions here to update the EOF. Failing to serialise
> -	 * here can result in EOF moving backwards and Bad Things Happen when
> -	 * that occurs.
> -	 *
> -	 * As IO completion only ever extends EOF, we can do an unlocked check
> -	 * here to avoid taking the spinlock. If we land within the current EOF,
> -	 * then we do not need to do an extending update at all, and we don't
> -	 * need to take the lock to check this. If we race with an update moving
> -	 * EOF, then we'll either still be beyond EOF and need to take the lock,
> -	 * or we'll be within EOF and we don't need to take it at all.
>  	 */
> -	if (offset + size <= i_size_read(inode))
> -		goto out;
> -
> -	spin_lock(&ip->i_flags_lock);
> -	if (offset + size > i_size_read(inode)) {
> -		i_size_write(inode, offset + size);
> -		spin_unlock(&ip->i_flags_lock);
> -		error = xfs_setfilesize(ip, offset, size);
> -	} else {
> -		spin_unlock(&ip->i_flags_lock);
> -	}
> +	error = xfs_dio_endio_set_isize(inode, offset, size);
>  
>  out:
>  	memalloc_nofs_restore(nofs_flag);


-- 
Damien Le Moal
Western Digital Research