Re: [Virtio-fs] [PATCH v3 19/26] DAX/unmap virtiofsd: Add wrappers for VHOST_USER_SLAVE_FS_IO

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Dr. David Alan Gilbert (git) (dgilbert@redhat.com) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Add a wrapper to send VHOST_USER_SLAVE_FS_IO commands and a
> further wrapper for sending a fuse_buf write using the FS_IO
> slave command.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  tools/virtiofsd/fuse_lowlevel.h | 25 +++++++++++++++++++
>  tools/virtiofsd/fuse_virtio.c   | 43 +++++++++++++++++++++++++++++++++
>  2 files changed, 68 insertions(+)
> 
> diff --git a/tools/virtiofsd/fuse_lowlevel.h b/tools/virtiofsd/fuse_lowlevel.h
> index 27b07bfc22..757cdae49b 100644
> --- a/tools/virtiofsd/fuse_lowlevel.h
> +++ b/tools/virtiofsd/fuse_lowlevel.h
> @@ -2013,4 +2013,29 @@ int64_t fuse_virtio_map(fuse_req_t req, VhostUserFSSlaveMsg *msg, int fd);
>   */
>  int64_t fuse_virtio_unmap(struct fuse_session *se, VhostUserFSSlaveMsg *msg);
>  
> +/**
> + * For use with virtio-fs; request IO directly to memory
> + *
> + * @param se The current session
> + * @param msg A set of IO requests
> + * @param fd The fd to map
> + * @return Length on success, negative errno on error
> + */
> +int64_t fuse_virtio_io(struct fuse_session *se, VhostUserFSSlaveMsg *msg,
> +                       int fd);
> +
> +/**
> + * For use with virtio-fs; wrapper for fuse_virtio_io for writes
> + * from memory to an fd
> + * @param req The request that triggered this action
> + * @param dst The destination (file) memory buffer
> + * @param dst_off Byte offset in the file
> + * @param src The source (memory) buffer
> + * @param src_off The GPA
> + * @param len Length in bytes
> + */
> +ssize_t fuse_virtio_write(fuse_req_t req, const struct fuse_buf *dst,
> +                          size_t dst_off, const struct fuse_buf *src,
> +                          size_t src_off, size_t len);
> +
>  #endif /* FUSE_LOWLEVEL_H_ */
> diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
> index 85d90ca595..91317bade8 100644
> --- a/tools/virtiofsd/fuse_virtio.c
> +++ b/tools/virtiofsd/fuse_virtio.c
> @@ -1141,3 +1141,46 @@ int64_t fuse_virtio_unmap(struct fuse_session *se, VhostUserFSSlaveMsg *msg)
>      return vu_fs_cache_request(&se->virtio_dev->dev, VHOST_USER_SLAVE_FS_UNMAP,
>                                 -1, msg);
>  }
> +
> +int64_t fuse_virtio_io(struct fuse_session *se, VhostUserFSSlaveMsg *msg,
> +                       int fd)
> +{
> +    if (!se->virtio_dev) {
> +        return -ENODEV;
> +    }
> +    return vu_fs_cache_request(&se->virtio_dev->dev, VHOST_USER_SLAVE_FS_IO,
> +                               fd, msg);
> +}
> +
> +/*
> + * Write to a file (dst) from an area of guest GPA (src) that probably
> + * isn't visible to the daemon.
> + */
> +ssize_t fuse_virtio_write(fuse_req_t req, const struct fuse_buf *dst,
> +                          size_t dst_off, const struct fuse_buf *src,
> +                          size_t src_off, size_t len)
> +{
> +    VhostUserFSSlaveMsg *msg = g_malloc0(sizeof(VhostUserFSSlaveMsg) +
> +                                         sizeof(VhostUserFSSlaveMsgEntry));
> +
> +    msg->count = 1;
> +
> +    if (dst->flags & FUSE_BUF_FD_SEEK) {
> +        msg->entries[0].fd_offset = dst->pos + dst_off;
> +    } else {
> +        off_t cur = lseek(dst->fd, 0, SEEK_CUR);
> +        if (cur == (off_t)-1) {
> +            g_free(msg);
> +            return -errno;
> +        }
> +        msg->entries[0].fd_offset = cur;
> +    }
> +    msg->entries[0].c_offset = (uintptr_t)src->mem + src_off;
> +    msg->entries[0].len = len;
> +    msg->entries[0].flags = VHOST_USER_FS_FLAG_MAP_W;
> +
> +    int64_t result = fuse_virtio_io(req->se, msg, dst->fd);
> +    fuse_log(FUSE_LOG_DEBUG, "%s: result=%" PRId64 " \n", __func__, result);

Oops, as the bot spotted, there's an unneeded space before the \n, I'll
sweep that out.

Dave

> +    g_free(msg);
> +    return result;
> +}
> -- 
> 2.31.1
> 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK