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Date:      Fri, 8 Feb 2019 08:20:19 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r343899 - head/sys/fs/nullfs
Message-ID:  <201902080820.x188KJpc024062@repo.freebsd.org>
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Author: kib
Date: Fri Feb  8 08:20:18 2019
New Revision: 343899
URL: https://svnweb.freebsd.org/changeset/base/343899

Log:
  Un null_vptocnp(), cache vp->v_mount and use it for null_nodeget() call.
  
  The vp vnode is unlocked during the execution of the VOP method and
  can be reclaimed, zeroing vp->v_data.  Caching allows to use the
  correct mount point.
  
  Reported and tested by:	pho
  PR: 235549
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

Modified:
  head/sys/fs/nullfs/null_vnops.c

Modified: head/sys/fs/nullfs/null_vnops.c
==============================================================================
--- head/sys/fs/nullfs/null_vnops.c	Fri Feb  8 08:17:31 2019	(r343898)
+++ head/sys/fs/nullfs/null_vnops.c	Fri Feb  8 08:20:18 2019	(r343899)
@@ -870,11 +870,14 @@ null_vptocnp(struct vop_vptocnp_args *ap)
 	struct vnode **dvp = ap->a_vpp;
 	struct vnode *lvp, *ldvp;
 	struct ucred *cred = ap->a_cred;
+	struct mount *mp;
 	int error, locked;
 
 	locked = VOP_ISLOCKED(vp);
 	lvp = NULLVPTOLOWERVP(vp);
 	vhold(lvp);
+	mp = vp->v_mount;
+	vfs_ref(mp);
 	VOP_UNLOCK(vp, 0); /* vp is held by vn_vptocnp_locked that called us */
 	ldvp = lvp;
 	vref(lvp);
@@ -882,6 +885,7 @@ null_vptocnp(struct vop_vptocnp_args *ap)
 	vdrop(lvp);
 	if (error != 0) {
 		vn_lock(vp, locked | LK_RETRY);
+		vfs_rel(mp);
 		return (ENOENT);
 	}
 
@@ -893,9 +897,10 @@ null_vptocnp(struct vop_vptocnp_args *ap)
 	if (error != 0) {
 		vrele(ldvp);
 		vn_lock(vp, locked | LK_RETRY);
+		vfs_rel(mp);
 		return (ENOENT);
 	}
-	error = null_nodeget(vp->v_mount, ldvp, dvp);
+	error = null_nodeget(mp, ldvp, dvp);
 	if (error == 0) {
 #ifdef DIAGNOSTIC
 		NULLVPTOLOWERVP(*dvp);
@@ -903,6 +908,7 @@ null_vptocnp(struct vop_vptocnp_args *ap)
 		VOP_UNLOCK(*dvp, 0); /* keep reference on *dvp */
 	}
 	vn_lock(vp, locked | LK_RETRY);
+	vfs_rel(mp);
 	return (error);
 }

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