lockd: handle test_lock deferrals

Rewrite nlmsvc_testlock() to use the new asynchronous interface: instead of
immediately doing a posix_test_lock(), we first look for a matching block.
If the subsequent test_lock returns anything other than -EINPROGRESS, we
then remove the block we've found and return the results.

If it returns -EINPROGRESS, then we defer the lock request.

In the case where the block we find in the first step has B_QUEUED set,
we bypass the vfs_test_lock entirely, instead using the block to decide how
to respond:
	with nlm_lck_denied if B_TIMED_OUT is set.
	with nlm_granted if B_GOT_CALLBACK is set.
	by dropping if neither B_TIMED_OUT nor B_GOT_CALLBACK is set

Signed-off-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/lockd/svcproc.c b/fs/lockd/svcproc.c
index d13b827dfd34..40b5cf496b51 100644
--- a/fs/lockd/svcproc.c
+++ b/fs/lockd/svcproc.c
@@ -33,6 +33,7 @@ cast_to_nlm(__be32 status, u32 vers)
                 case nlm_lck_denied_nolocks:
                 case nlm_lck_blocked:
                 case nlm_lck_denied_grace_period:
+                case nlm_drop_reply:
                         break;
                 case nlm4_deadlock:
                         status = nlm_lck_denied;
@@ -128,6 +129,8 @@ nlmsvc_proc_test(struct svc_rqst *rqstp, struct nlm_args *argp,
 
         /* Now check for conflicting locks */
         resp->status = cast_status(nlmsvc_testlock(rqstp, file, &argp->lock, &resp->lock, &resp->cookie));
+        if (resp->status == nlm_drop_reply)
+                return rpc_drop_reply;
 
         dprintk("lockd: TEST          status %d vers %d\n",
                 ntohl(resp->status), rqstp->rq_vers);