virtiofs: Fail dax mount if device does not support it

Right now "mount -t virtiofs -o dax myfs /mnt/virtiofs" succeeds even if filesystem deivce does not have a cache window and hence DAX can't be supported. This gives a false sense to user that they are using DAX with virtiofs but fact of the matter is that they are not. Fix this by returning error if dax can't be supported and user has asked for it. Signed-off-by: Vivek Goyal <[email protected]> Reviewed-by: Stefan Hajnoczi <[email protected]> Signed-off-by: Miklos Szeredi <[email protected]>
niw · Mar 5, 2021 · 3f9b9ef · 3f9b9ef
1 parent 775c503
commit 3f9b9ef
Showing 1 changed file with 8 additions and 1 deletion.
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
@@ -1324,8 +1324,15 @@ static int virtio_fs_fill_super(struct super_block *sb, struct fs_context *fsc)
 
 	/* virtiofs allocates and installs its own fuse devices */
 	ctx->fudptr = NULL;
-	if (ctx->dax)
+	if (ctx->dax) {
+		if (!fs->dax_dev) {
+			err = -EINVAL;
+			pr_err("virtio-fs: dax can't be enabled as filesystem"
+			       " device does not support it.\n");
+			goto err_free_fuse_devs;
+		}
 		ctx->dax_dev = fs->dax_dev;
+	}
 	err = fuse_fill_super_common(sb, ctx);
 	if (err < 0)
 		goto err_free_fuse_devs;