[src/trunk]: src/sys/kern It is wrong to block the vnode during vcache_rekey....

[hannken <hannken%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/442240632908
branches:  trunk
changeset: 349894:442240632908
user:      hannken <hannken%NetBSD.org@localhost>
date:      Tue Dec 27 11:59:36 2016 +0000

description:
It is wrong to block the vnode during vcache_rekey.  The vnode may be looked
up using the old key until vcache_rekey_exit changes the key to the new one.

Add an assertion that the temporary key is different from the current one.

diffstat:

 sys/kern/vfs_vnode.c |  18 ++++++------------
 1 files changed, 6 insertions(+), 12 deletions(-)

diffs (69 lines):

diff -r 954cbfa30790 -r 442240632908 sys/kern/vfs_vnode.c
--- a/sys/kern/vfs_vnode.c      Tue Dec 27 11:17:51 2016 +0000
+++ b/sys/kern/vfs_vnode.c      Tue Dec 27 11:59:36 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_vnode.c,v 1.64 2016/12/20 10:02:21 hannken Exp $   */
+/*     $NetBSD: vfs_vnode.c,v 1.65 2016/12/27 11:59:36 hannken Exp $   */
 
 /*-
  * Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@@ -156,7 +156,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.64 2016/12/20 10:02:21 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.65 2016/12/27 11:59:36 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -1305,7 +1305,7 @@
 }
 
 /*
- * Prepare key change: lock old and new cache node.
+ * Prepare key change: update old cache nodes key and lock new cache node.
  * Return an error if the new node already exists.
  */
 int
@@ -1345,20 +1345,18 @@
        SLIST_INSERT_HEAD(&vcache.hashtab[new_hash & vcache.hashmask],
            new_node, vi_hash);
 
-       /* Lock old node. */
+       /* Replace old nodes key with the temporary copy. */
        node = vcache_hash_lookup(&old_vcache_key, old_hash);
        KASSERT(node != NULL);
        KASSERT(VIMPL_TO_VNODE(node) == vp);
-       mutex_enter(vp->v_interlock);
-       VSTATE_CHANGE(vp, VS_ACTIVE, VS_BLOCKED);
+       KASSERT(node->vi_key.vk_key != old_vcache_key.vk_key);
        node->vi_key = old_vcache_key;
-       mutex_exit(vp->v_interlock);
        mutex_exit(&vcache.lock);
        return 0;
 }
 
 /*
- * Key change complete: remove old node and unlock new node.
+ * Key change complete: update old node and remove placeholder.
  */
 void
 vcache_rekey_exit(struct mount *mp, struct vnode *vp,
@@ -1386,8 +1384,6 @@
        old_node = vcache_hash_lookup(&old_vcache_key, old_hash);
        KASSERT(old_node != NULL);
        KASSERT(VIMPL_TO_VNODE(old_node) == vp);
-       mutex_enter(vp->v_interlock);
-       VSTATE_ASSERT(vp, VS_BLOCKED);
 
        new_node = vcache_hash_lookup(&new_vcache_key, new_hash);
        KASSERT(new_node != NULL);
@@ -1404,8 +1400,6 @@
                SLIST_INSERT_HEAD(&vcache.hashtab[new_hash & vcache.hashmask],
                    old_node, vi_hash);
        }
-       VSTATE_CHANGE(vp, VS_BLOCKED, VS_ACTIVE);
-       mutex_exit(vp->v_interlock);
 
        /* Remove new node used as placeholder. */
        SLIST_REMOVE(&vcache.hashtab[new_hash & vcache.hashmask],