Re: [PATCH v2 19/23] xfs: disable direct read path for fs-verity sealed files

Darrick J. Wong
2023-04-04T16:10:47Z

On Tue, Apr 04, 2023 at 04:53:15PM +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 947b5c436172..9e072e82f6c1 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;
> ret = xfs_file_buffered_read(iocb, to);

XFS doesn't usually allow directio fallback to the pagecache. Why would
fsverity be any different?

--D

> + }
>
> if (ret > 0)
> XFS_STATS_ADD(mp, xs_read_bytes, ret);
> --
> 2.38.4
>