Re: [PATCH v5 20/24] xfs: disable direct read path for fs-verity files

Darrick J. Wong
2024-03-07T22:11:08Z

On Mon, Mar 04, 2024 at 08:10:43PM +0100, 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 | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 17404c2e7e31..af3201075066 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -281,7 +281,8 @@ 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);
> @@ -334,10 +335,18 @@ 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 {

I think the earlier cases need curly braces {} too.

> + /*
> + * 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 (see
> + * generic_file_read_iter())
> + */
> + iocb->ki_flags &= ~IOCB_DIRECT;

I'm curious that you added this flag here; how have we gotten along
this far without clearing it?

--D

> ret = xfs_file_buffered_read(iocb, to);
> + }
>
> if (ret > 0)
> XFS_STATS_ADD(mp, xs_read_bytes, ret);
> --
> 2.42.0
>
>