nfs/blocklayout: add support for NVMe

Look for the udev generated persistent device name for NVMe devices
in addition to the SCSI ones and the Redhat-specific device mapper
name.

This is the client side implementation of RFC 9561 "Using the Parallel
NFS (pNFS) SCSI Layout to Access Non-Volatile Memory Express (NVMe)
Storage Devices".

Note that the udev rules for nvme are a bit of a mess and udev will only
create a link for the uuid if the NVMe namespace has one, and not the
NGUID.  As the current RFCs don't support UUID based identifications this
means the layout can't be used on such namespaces out of the box.  A
small tweak to the udev rules can work around it, and as the real fix I
will submit a draft to the IETF NFSv4 working group to support UUID-based
identifiers for SCSI and NVMe.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Sagi Grimberg <[email protected]>
Reviewed-by: Benjamin Coddington <[email protected]>
Signed-off-by: Anna Schumaker <[email protected]>

Author: Christoph Hellwig

fs/nfs/blocklayout/dev.c

@@ -404,6 +404,8 @@ bl_parse_scsi(struct nfs_server *server, struct pnfs_block_dev *d,
 	bdev_file = bl_open_path(v, "dm-uuid-mpath-0x");
 	if (IS_ERR(bdev_file))
 		bdev_file = bl_open_path(v, "wwn-0x");
+	if (IS_ERR(bdev_file))
+		bdev_file = bl_open_path(v, "nvme-eui.");
 	if (IS_ERR(bdev_file)) {
 		pr_warn("pNFS: no device found for volume %*phN\n",
 			v->scsi.designator_len, v->scsi.designator);