lockd: add code to handle deferred lock requests

Rewrite nlmsvc_lock() to use the asynchronous interface.

As with testlock, we answer nlm requests in nlmsvc_lock by first looking up
the block and then using the results we find in the block if B_QUEUED is
set, and calling vfs_lock_file() otherwise.

If this a new lock request and we get -EINPROGRESS return on a non-blocking
request then we defer the request.

Also modify nlmsvc_unlock() to call the filesystem method if appropriate.

Signed-off-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/fs/lockd/svcsubs.c b/fs/lockd/svcsubs.c
index 5095708..84ebba3 100644
--- a/fs/lockd/svcsubs.c
+++ b/fs/lockd/svcsubs.c
@@ -182,7 +182,7 @@
 			lock.fl_type  = F_UNLCK;
 			lock.fl_start = 0;
 			lock.fl_end   = OFFSET_MAX;
-			if (posix_lock_file(file->f_file, &lock, NULL) < 0) {
+			if (vfs_lock_file(file->f_file, F_SETLK, &lock, NULL) < 0) {
 				printk("lockd: unlock failure in %s:%d\n",
 						__FILE__, __LINE__);
 				return 1;