[PATCH 2/2] nfs/blocklayout: Limit repeat device registration on failure

[Benjamin Coddington <bcodding@redhat.com>]

If we're unable to register a SCSI device, ensure we mark the device as
unavailable so that it will timeout and be re-added via GETDEVINFO.  This
avoids repeated doomed attempts to register a device in the IO path.

Add some clarifying comments as well.

Fixes: d869da91cccb ("nfs/blocklayout: Fix premature PR key unregistration")
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
---
 fs/nfs/blocklayout/blocklayout.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 0becdec12970..b36bc2f4f7e2 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -571,19 +571,29 @@ bl_find_get_deviceid(struct nfs_server *server,
 	if (!node)
 		return ERR_PTR(-ENODEV);
 
+	/*
+	 * Devices that are marked unavailable are left in the cache with a
+	 * timeout to avoid sending GETDEVINFO after every LAYOUTGET, or
+	 * constantly attempting to register the device.  Once marked as
+	 * unavailable they must be deleted and never reused.
+	 */
 	if (test_bit(NFS_DEVICEID_UNAVAILABLE, &node->flags)) {
 		unsigned long end = jiffies;
 		unsigned long start = end - PNFS_DEVICE_RETRY_TIMEOUT;
 
 		if (!time_in_range(node->timestamp_unavailable, start, end)) {
+			/* Force a new GETDEVINFO for this LAYOUT */
 			nfs4_delete_deviceid(node->ld, node->nfs_client, id);
 			goto retry;
 		}
 		goto out_put;
 	}
 
-	if (!bl_register_dev(container_of(node, struct pnfs_block_dev, node)))
+	/* If we cannot register, treat this device as transient */
+	if (!bl_register_dev(container_of(node, struct pnfs_block_dev, node))) {
+		nfs4_mark_deviceid_unavailable(node);
 		goto out_put;
+	}
 
 	return node;
 
-- 
2.47.0