NLM/NFS: Use cached nlm_host when calling nlmclnt_proc()

Now that each NFS mount point caches its own nlm_host structure, it can be
passed to nlmclnt_proc() for each lock request.  By pinning an nlm_host for
each mount point, we trade the overhead of looking up or creating a fresh
nlm_host struct during every NLM procedure call for a little extra memory.

We also restrict the nlmclnt_proc symbol to limit the use of this call to
in-tree modules.

Note that nlm_lookup_host() (just removed from the client's per-request
NLM processing) could also trigger an nlm_host garbage collection.  Now
client-side nlm_host garbage collection occurs only during NFS mount
processing.  Since the NFS client now holds a reference on these nlm_host
structures, they wouldn't have been affected by garbage collection
anyway.

Given that nlm_lookup_host() reorders the global nlm_host chain after
every successful lookup, and that a garbage collection could be triggered
during the call, we've removed a significant amount of per-NLM-request
CPU processing overhead.

Sidebar: there are only a few remaining references to the internals of
NFS inodes in the client-side NLM code.  The only references I found are
related to extracting or comparing the inode's file handle via NFS_FH().
One is in nlmclnt_grant(); the other is in nlmclnt_setlockargs().

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c
index c9f46a24e75c..5ccf7faee19c 100644
--- a/fs/nfs/proc.c
+++ b/fs/nfs/proc.c
@@ -593,7 +593,9 @@ nfs_proc_commit_setup(struct nfs_write_data *data, struct rpc_message *msg)
 static int
 nfs_proc_lock(struct file *filp, int cmd, struct file_lock *fl)
 {
-	return nlmclnt_proc(filp->f_path.dentry->d_inode, cmd, fl);
+	struct inode *inode = filp->f_path.dentry->d_inode;
+
+	return nlmclnt_proc(NFS_SERVER(inode)->nlm_host, cmd, fl);
 }