[src/trunk]: src/sys/kern Add flag VRELEL_FORCE_RELE to vrelel() to force rel...

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

details:   https://anonhg.NetBSD.org/src/rev/7ba4486dbac9
branches:  trunk
changeset: 822650:7ba4486dbac9
user:      hannken <hannken%NetBSD.org@localhost>
date:      Thu Mar 30 09:14:08 2017 +0000

description:
Add flag VRELEL_FORCE_RELE to vrelel() to force release and
use it from vdrain_vrele() and vrele_flush() to prevent a
possible live lock from vrele_flush().

diffstat:

 sys/kern/vfs_vnode.c |  20 ++++++++++++--------
 1 files changed, 12 insertions(+), 8 deletions(-)

diffs (76 lines):

diff -r 41f47e777715 -r 7ba4486dbac9 sys/kern/vfs_vnode.c
--- a/sys/kern/vfs_vnode.c      Thu Mar 30 09:13:37 2017 +0000
+++ b/sys/kern/vfs_vnode.c      Thu Mar 30 09:14:08 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_vnode.c,v 1.77 2017/03/30 09:12:21 hannken Exp $   */
+/*     $NetBSD: vfs_vnode.c,v 1.78 2017/03/30 09:14:08 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 1.77 2017/03/30 09:12:21 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_vnode.c,v 1.78 2017/03/30 09:14:08 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -184,6 +184,7 @@
 
 /* Flags to vrelel. */
 #define        VRELEL_ASYNC_RELE       0x0001  /* Always defer to vrele thread. */
+#define        VRELEL_FORCE_RELE       0x0002  /* Must always succeed. */
 
 u_int                  numvnodes               __cacheline_aligned;
 
@@ -482,7 +483,8 @@
                TAILQ_INSERT_TAIL(vip->vi_lrulisthd, vip, vi_lrulist);
                mutex_exit(&vdrain_lock);
 
-               vrele(VIMPL_TO_VNODE(vip));
+               mutex_enter(VIMPL_TO_VNODE(vip)->v_interlock);
+               vrelel(VIMPL_TO_VNODE(vip), VRELEL_FORCE_RELE);
 
                mutex_enter(&vdrain_lock);
        }
@@ -523,8 +525,10 @@
        mutex_exit(&vdrain_lock);
 
        if (vcache_vget(vp) == 0) {
-               if (!vrecycle(vp))
-                       vrele(vp);
+               if (!vrecycle(vp)) {
+                       mutex_enter(vp->v_interlock);
+                       vrelel(vp, VRELEL_FORCE_RELE);
+               }
        }
        fstrans_done(mp);
 
@@ -561,7 +565,7 @@
        mutex_exit(&vdrain_lock);
 
        mutex_enter(vp->v_interlock);
-       vrelel(vp, 0);
+       vrelel(vp, VRELEL_FORCE_RELE);
        fstrans_done(mp);
 
        mutex_enter(&vdrain_lock);
@@ -704,7 +708,7 @@
                if ((curlwp == uvm.pagedaemon_lwp) ||
                    (flags & VRELEL_ASYNC_RELE) != 0) {
                        defer = true;
-               } else if (curlwp == vdrain_lwp) {
+               } else if ((flags & VRELEL_FORCE_RELE) != 0) {
                        /*
                         * We have to try harder.
                         */
@@ -723,7 +727,7 @@
                }
 
                KASSERT(mutex_owned(vp->v_interlock));
-               KASSERT(! (curlwp == vdrain_lwp && defer));
+               KASSERT(! ((flags & VRELEL_FORCE_RELE) != 0 && defer));
 
                if (defer) {
                        /*