nfsd/blocklayout: pretend we can send deviceid notifications

Commit df52699e4fcef ("NFSv4.1: Don't cache deviceids that have no
notifications") causes the Linux NFS client to stop caching deviceid's
unless a server pretends to support deviceid notifications.  While this
behavior is stupid and the language around this area in rfc5661 is a
mess carified by an errata that I submittted, Trond insists on this
behavior.  Not caching deviceids degrades block layout performance
massively as a GETDEVICEINFO is fairly expensive.

So add this hack to make the Linux client happy again.

Cc: stable@vger.kernel.org
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
index 03d647bf195d78bb3d6611553c9ad3e6fa4385a2..cdefaa331a0719e88df91ef7c04c32706ae199a1 100644 (file)
--- a/fs/nfsd/blocklayout.c
+++ b/fs/nfsd/blocklayout.c
@@ -181,6 +181,17 @@ nfsd4_block_proc_layoutcommit(struct inode *inode,
 }
 
 const struct nfsd4_layout_ops bl_layout_ops = {
+       /*
+        * Pretend that we send notification to the client.  This is a blatant
+        * lie to force recent Linux clients to cache our device IDs.
+        * We rarely ever change the device ID, so the harm of leaking deviceids
+        * for a while isn't too bad.  Unfortunately RFC5661 is a complete mess
+        * in this regard, but I filed errata 4119 for this a while ago, and
+        * hopefully the Linux client will eventually start caching deviceids
+        * without this again.
+        */
+       .notify_types           =
+                       NOTIFY_DEVICEID4_DELETE | NOTIFY_DEVICEID4_CHANGE,
        .proc_getdeviceinfo     = nfsd4_block_proc_getdeviceinfo,
        .encode_getdeviceinfo   = nfsd4_block_encode_getdeviceinfo,
        .proc_layoutget         = nfsd4_block_proc_layoutget,