nfs/blocklayout: refactor block device opening

Deduplicate the helpers to open a device node by passing a name
prefix argument and using the same helper for both kinds of paths.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/blocklayout/dev.c

@@ -301,18 +301,14 @@ bl_validate_designator(struct pnfs_block_volume *v)
 	}
 }
 
-/*
- * Try to open the udev path for the WWN.  At least on Debian the udev
- * by-id path will always point to the dm-multipath device if one exists.
- */
 static struct block_device *
-bl_open_udev_path(struct pnfs_block_volume *v)
+bl_open_path(struct pnfs_block_volume *v, const char *prefix)
 {
 	struct block_device *bdev;
 	const char *devname;
 
-	devname = kasprintf(GFP_KERNEL, "/dev/disk/by-id/wwn-0x%*phN",
-				v->scsi.designator_len, v->scsi.designator);
+	devname = kasprintf(GFP_KERNEL, "/dev/disk/by-id/%s%*phN",
+			prefix, v->scsi.designator_len, v->scsi.designator);
 	if (!devname)
 		return ERR_PTR(-ENOMEM);
 
@@ -326,28 +322,6 @@ bl_open_udev_path(struct pnfs_block_volume *v)
 	return bdev;
 }
 
-/*
- * Try to open the RH/Fedora specific dm-mpath udev path for this WWN, as the
- * wwn- links will only point to the first discovered SCSI device there.
- */
-static struct block_device *
-bl_open_dm_mpath_udev_path(struct pnfs_block_volume *v)
-{
-	struct block_device *bdev;
-	const char *devname;
-
-	devname = kasprintf(GFP_KERNEL,
-			"/dev/disk/by-id/dm-uuid-mpath-%d%*phN",
-			v->scsi.designator_type,
-			v->scsi.designator_len, v->scsi.designator);
-	if (!devname)
-		return ERR_PTR(-ENOMEM);
-
-	bdev = blkdev_get_by_path(devname, FMODE_READ | FMODE_WRITE, NULL);
-	kfree(devname);
-	return bdev;
-}
-
 static int
 bl_parse_scsi(struct nfs_server *server, struct pnfs_block_dev *d,
 		struct pnfs_block_volume *volumes, int idx, gfp_t gfp_mask)
@@ -360,9 +334,15 @@ bl_parse_scsi(struct nfs_server *server, struct pnfs_block_dev *d,
 	if (!bl_validate_designator(v))
 		return -EINVAL;
 
-	bdev = bl_open_dm_mpath_udev_path(v);
+	/*
+	 * Try to open the RH/Fedora specific dm-mpath udev path first, as the
+	 * wwn- links will only point to the first discovered SCSI device there.
+	 * On other distributions like Debian, the default SCSI by-id path will
+	 * point to the dm-multipath device if one exists.
+	 */
+	bdev = bl_open_path(v, "dm-uuid-mpath-0x");
 	if (IS_ERR(bdev))
-		bdev = bl_open_udev_path(v);
+		bdev = bl_open_path(v, "wwn-0x");
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
 	d->bdev = bdev;