Re: [PATCH v3 24/28] xfs: disable direct read path for fs-verity sealed files

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Oct 06, 2023 at 08:49:18PM +0200, Andrey Albershteyn wrote:
> The direct path is not supported on verity files. Attempts to use direct
> I/O path on such files should fall back to buffered I/O path.
> 
> Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
> ---
>  fs/xfs/xfs_file.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index a92c8197c26a..7363cbdff803 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -244,7 +244,8 @@ xfs_file_dax_read(
>  	struct kiocb		*iocb,
>  	struct iov_iter		*to)
>  {
> -	struct xfs_inode	*ip = XFS_I(iocb->ki_filp->f_mapping->host);
> +	struct inode		*inode = iocb->ki_filp->f_mapping->host;
> +	struct xfs_inode	*ip = XFS_I(inode);
>  	ssize_t			ret = 0;
>  
>  	trace_xfs_file_dax_read(iocb, to);
> @@ -297,10 +298,17 @@ xfs_file_read_iter(
>  
>  	if (IS_DAX(inode))
>  		ret = xfs_file_dax_read(iocb, to);
> -	else if (iocb->ki_flags & IOCB_DIRECT)
> +	else if (iocb->ki_flags & IOCB_DIRECT && !fsverity_active(inode))
>  		ret = xfs_file_dio_read(iocb, to);
> -	else
> +	else {
> +		/*
> +		 * In case fs-verity is enabled, we also fallback to the
> +		 * buffered read from the direct read path. Therefore,
> +		 * IOCB_DIRECT is set and need to be cleared
> +		 */
> +		iocb->ki_flags &= ~IOCB_DIRECT;

We don't clear IOCB_DIRECT when directio writes fall back to buffered
writes; why is it necessary here?

--D

>  		ret = xfs_file_buffered_read(iocb, to);
> +	}
>  
>  	if (ret > 0)
>  		XFS_STATS_ADD(mp, xs_read_bytes, ret);
> -- 
> 2.40.1
>