wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index c82a212..9cce670 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -940,7 +940,7 @@
 	dfprintk(FILE, "NFS: llseek dir(%pD2, %lld, %d)\n",
 			filp, offset, whence);
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 	switch (whence) {
 		case 1:
 			offset += filp->f_pos;
@@ -957,7 +957,7 @@
 		dir_ctx->duped = 0;
 	}
 out:
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 	return offset;
 }
 
@@ -972,9 +972,9 @@
 
 	dfprintk(FILE, "NFS: fsync dir(%pD2) datasync %d\n", filp, datasync);
 
-	mutex_lock(&inode->i_mutex);
+	inode_lock(inode);
 	nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
-	mutex_unlock(&inode->i_mutex);
+	inode_unlock(inode);
 	return 0;
 }