From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Tue, 15 Nov 2011 23:11:58 +0000 (-0800)
Subject: kernel - Try to fix vrevoke() race/crash
X-Git-Tag: v3.0.0~654
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/d557dd6d0198bfb5650b6a3ceafd7c1d1711cab5

kernel - Try to fix vrevoke() race/crash

* Try to fix situations where inactive vnodes are assocatied with a
  device.

Reported-by: marino
---

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index f7da2d29e6..79868f264c 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1325,16 +1325,25 @@ vrevoke(struct vnode *vp, struct ucred *cred)
 	reference_dev(dev);
 	lwkt_gettoken(&spechash_token);
 
+restart:
 	vqn = SLIST_FIRST(&dev->si_hlist);
 	if (vqn)
-		vref(vqn);
+		vhold(vqn);
 	while ((vq = vqn) != NULL) {
-		vqn = SLIST_NEXT(vqn, v_cdevnext);
+		if (sysref_isactive(&vq->v_sysref)) {
+			vref(vq);
+			fdrevoke(vq, DTYPE_VNODE, cred);
+			/*v_release_rdev(vq);*/
+			vrele(vq);
+			if (vq->v_rdev != dev) {
+				vdrop(vq);
+				goto restart;
+			}
+		}
+		vqn = SLIST_NEXT(vq, v_cdevnext);
 		if (vqn)
-			vref(vqn);
-		fdrevoke(vq, DTYPE_VNODE, cred);
-		/*v_release_rdev(vq);*/
-		vrele(vq);
+			vhold(vqn);
+		vdrop(vq);
 	}
 	lwkt_reltoken(&spechash_token);
 	dev_drevoke(dev);