nfs/blocklayout: refactor open-by-wwn

The current code works with the standard udev/systemd names, but we'll have
to add another method in the next patch.  Refactor it into a separate helper
to make room for the new variant.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 27 insertions, 26 deletions

diff --git a/fs/nfs/blocklayout/dev.c b/fs/nfs/blocklayout/dev.c
index 7fb9c07c078c..ea70883a174a 100644
--- a/fs/nfs/blocklayout/dev.c
+++ b/fs/nfs/blocklayout/dev.c
@@ -287,44 +287,45 @@ 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)
+{
+        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);
+        if (!devname)
+                return ERR_PTR(-ENOMEM);
+
+        bdev = blkdev_get_by_path(devname, FMODE_READ | FMODE_WRITE, NULL);
+        if (IS_ERR(bdev)) {
+                pr_warn("pNFS: failed to open device %s (%ld)\n",
+                        devname, PTR_ERR(bdev));
+        }
+
+        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)
 {
         struct pnfs_block_volume *v = &volumes[idx];
         const struct pr_ops *ops;
-        const char *devname;
         int error;
 
         if (!bl_validate_designator(v))
                 return -EINVAL;
 
-        switch (v->scsi.designator_len) {
-        case 8:
-                devname = kasprintf(GFP_KERNEL, "/dev/disk/by-id/wwn-0x%8phN",
-                                v->scsi.designator);
-                break;
-        case 12:
-                devname = kasprintf(GFP_KERNEL, "/dev/disk/by-id/wwn-0x%12phN",
-                                v->scsi.designator);
-                break;
-        case 16:
-                devname = kasprintf(GFP_KERNEL, "/dev/disk/by-id/wwn-0x%16phN",
-                                v->scsi.designator);
-                break;
-        default:
-                return -EINVAL;
-        }
-
-        d->bdev = blkdev_get_by_path(devname, FMODE_READ | FMODE_WRITE, NULL);
-        if (IS_ERR(d->bdev)) {
-                pr_warn("pNFS: failed to open device %s (%ld)\n",
-                        devname, PTR_ERR(d->bdev));
-                kfree(devname);
+        d->bdev = bl_open_udev_path(v);
+        if (IS_ERR(d->bdev))
                 return PTR_ERR(d->bdev);
-        }
-
-        kfree(devname);
 
         d->len = i_size_read(d->bdev->bd_inode);
         d->map = bl_map_simple;