[PATCH v3 2/2] nfs/blocklayout: Limit repeat device registration on failure

Benjamin Coddington
2024-11-22T12:48:04Z

Every pNFS SCSI IO wants to do LAYOUTGET, then within the layout find the
device which can drive GETDEVINFO, then finally may need to prep the device
with a reservation. This slow work makes a mess of IO latencies if one of
the later steps is going to fail for awhile.

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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
---
fs/nfs/blocklayout/blocklayout.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 0becdec12970..47189476b553 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -571,19 +571,32 @@ 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)) {
+ /* Uncork subsequent GETDEVINFO operations for this device */
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 (!bl_register_dev(container_of(node, struct pnfs_block_dev, node))) {
+ /*
+ * If we cannot register, treat this device as transient:
+ * Make a negative cache entry for the device
+ */
+ nfs4_mark_deviceid_unavailable(node);
goto out_put;
+ }

return node;

--
2.47.0