locks: add a dedicated spinlock to protect i_flctx lists

We can now add a dedicated spinlock without expanding struct inode.
Change to using that to protect the various i_flctx lists.

Signed-off-by: Jeff Layton <jlayton@primarydata.com>
Acked-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 6084c26..a3bb22a 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -1376,12 +1376,12 @@
 
 	/* Guard against delegation returns and new lock/unlock calls */
 	down_write(&nfsi->rwsem);
-	spin_lock(&inode->i_lock);
+	spin_lock(&flctx->flc_lock);
 restart:
 	list_for_each_entry(fl, list, fl_list) {
 		if (nfs_file_open_context(fl->fl_file)->state != state)
 			continue;
-		spin_unlock(&inode->i_lock);
+		spin_unlock(&flctx->flc_lock);
 		status = ops->recover_lock(state, fl);
 		switch (status) {
 		case 0:
@@ -1408,13 +1408,13 @@
 			/* kill_proc(fl->fl_pid, SIGLOST, 1); */
 			status = 0;
 		}
-		spin_lock(&inode->i_lock);
+		spin_lock(&flctx->flc_lock);
 	}
 	if (list == &flctx->flc_posix) {
 		list = &flctx->flc_flock;
 		goto restart;
 	}
-	spin_unlock(&inode->i_lock);
+	spin_unlock(&flctx->flc_lock);
 out:
 	up_write(&nfsi->rwsem);
 	return status;