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Date:      Fri, 15 Feb 2019 11:19:12 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org
Subject:   svn commit: r344153 - stable/12/sys/fs/nullfs
Message-ID:  <201902151119.x1FBJCB8049697@repo.freebsd.org>
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Author: kib
Date: Fri Feb 15 11:19:12 2019
New Revision: 344153
URL: https://svnweb.freebsd.org/changeset/base/344153

Log:
  MFC r343897, r343898:
  Some style for nullfs_mount().
  Before using VTONULL(), check that the covered vnode belongs to nullfs.

Modified:
  stable/12/sys/fs/nullfs/null_vfsops.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/fs/nullfs/null_vfsops.c
==============================================================================
--- stable/12/sys/fs/nullfs/null_vfsops.c	Fri Feb 15 11:13:39 2019	(r344152)
+++ stable/12/sys/fs/nullfs/null_vfsops.c	Fri Feb 15 11:19:12 2019	(r344153)
@@ -74,13 +74,14 @@ static vfs_extattrctl_t	nullfs_extattrctl;
 static int
 nullfs_mount(struct mount *mp)
 {
-	int error = 0;
 	struct vnode *lowerrootvp, *vp;
 	struct vnode *nullm_rootvp;
 	struct null_mount *xmp;
+	struct null_node *nn;
+	struct nameidata nd, *ndp;
 	char *target;
-	int isvnunlocked = 0, len;
-	struct nameidata nd, *ndp = &nd;
+	int error, len;
+	bool isvnunlocked;
 
 	NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);
 
@@ -110,14 +111,18 @@ nullfs_mount(struct mount *mp)
 	/*
 	 * Unlock lower node to avoid possible deadlock.
 	 */
-	if ((mp->mnt_vnodecovered->v_op == &null_vnodeops) &&
+	if (mp->mnt_vnodecovered->v_op == &null_vnodeops &&
 	    VOP_ISLOCKED(mp->mnt_vnodecovered) == LK_EXCLUSIVE) {
 		VOP_UNLOCK(mp->mnt_vnodecovered, 0);
-		isvnunlocked = 1;
+		isvnunlocked = true;
+	} else {
+		isvnunlocked = false;
 	}
+
 	/*
 	 * Find lower node
 	 */
+	ndp = &nd;
 	NDINIT(ndp, LOOKUP, FOLLOW|LOCKLEAF, UIO_SYSSPACE, target, curthread);
 	error = namei(ndp);
 
@@ -140,10 +145,13 @@ nullfs_mount(struct mount *mp)
 	/*
 	 * Check multi null mount to avoid `lock against myself' panic.
 	 */
-	if (lowerrootvp == VTONULL(mp->mnt_vnodecovered)->null_lowervp) {
-		NULLFSDEBUG("nullfs_mount: multi null mount?\n");
-		vput(lowerrootvp);
-		return (EDEADLK);
+	if (mp->mnt_vnodecovered->v_op == &null_vnodeops) {
+		nn = VTONULL(mp->mnt_vnodecovered);
+		if (nn == NULL || lowerrootvp == nn->null_lowervp) {
+			NULLFSDEBUG("nullfs_mount: multi null mount?\n");
+			vput(lowerrootvp);
+			return (EDEADLK);
+		}
 	}
 
 	xmp = (struct null_mount *) malloc(sizeof(struct null_mount),

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