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Date:      Mon, 16 May 2016 06:24:04 +0000 (UTC)
From:      Andriy Gapon <avg@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r299900 - in head/sys/cddl: compat/opensolaris/kern contrib/opensolaris/uts/common/fs/zfs
Message-ID:  <201605160624.u4G6O44s060371@repo.freebsd.org>
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Author: avg
Date: Mon May 16 06:24:04 2016
New Revision: 299900
URL: https://svnweb.freebsd.org/changeset/base/299900

Log:
  zfsctl: fix several problems with reference counts
  
  * Remove excessive references on a snapshot mountpoint vnode.
    zfsctl_snapdir_lookup() called VN_HOLD() on a vnode returned from
    zfsctl_snapshot_mknode() and the latter also had a call to VN_HOLD()
    on the same vnode.
    On top of that gfs_dir_create() already returns the vnode with the
    use count of 1 (set in getnewvnode).
    So there was 3 references on the vnode.
  
  * mount_snapshot() should keep a reference to a covered vnode.
    That reference is owned by the mountpoint (mounted snapshot filesystem).
  
  * Remove cryptic manipulations of a covered vnode in zfs_umount().
    FreeBSD dounmount() already does the right thing and releases the covered
    vnode.
  
  PR:		207464
  Reported by:	dustinwenz@ebureau.com
  Tested by:	Howard Powell <hpowell@lighthouseinstruments.com>
  MFC after:	3 weeks

Modified:
  head/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c
  head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c

Modified: head/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c
==============================================================================
--- head/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c	Mon May 16 06:19:17 2016	(r299899)
+++ head/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c	Mon May 16 06:24:04 2016	(r299900)
@@ -229,7 +229,7 @@ mount_snapshot(kthread_t *td, vnode_t **
 	vfs_event_signal(NULL, VQ_MOUNT, 0);
 	if (VFS_ROOT(mp, LK_EXCLUSIVE, &mvp))
 		panic("mount: lost mount");
-	vput(vp);
+	VOP_UNLOCK(vp, 0);
 	vfs_unbusy(mp);
 	*vpp = mvp;
 	return (0);

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c	Mon May 16 06:19:17 2016	(r299899)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c	Mon May 16 06:24:04 2016	(r299900)
@@ -1076,7 +1076,6 @@ zfsctl_snapdir_lookup(ap)
 	sep->se_name = kmem_alloc(strlen(nm) + 1, KM_SLEEP);
 	(void) strcpy(sep->se_name, nm);
 	*vpp = sep->se_root = zfsctl_snapshot_mknode(dvp, dmu_objset_id(snap));
-	VN_HOLD(*vpp);
 	avl_insert(&sdp->sd_snaps, sep, where);
 
 	dmu_objset_rele(snap, FTAG);
@@ -1454,7 +1453,6 @@ zfsctl_snapshot_mknode(vnode_t *pvp, uin
 
 	vp = gfs_dir_create(sizeof (zfsctl_node_t), pvp, pvp->v_vfsp,
 	    &zfsctl_ops_snapshot, NULL, NULL, MAXNAMELEN, NULL, NULL);
-	VN_HOLD(vp);
 	zcp = vp->v_data;
 	zcp->zc_id = objset;
 	VOP_UNLOCK(vp, 0);

Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c	Mon May 16 06:19:17 2016	(r299899)
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c	Mon May 16 06:24:04 2016	(r299900)
@@ -2005,12 +2005,6 @@ zfs_umount(vfs_t *vfsp, int fflag)
 	 */
 	if (zfsvfs->z_ctldir != NULL)
 		zfsctl_destroy(zfsvfs);
-	if (zfsvfs->z_issnap) {
-		vnode_t *svp = vfsp->mnt_vnodecovered;
-
-		if (svp->v_count >= 2)
-			VN_RELE(svp);
-	}
 	zfs_freevfs(vfsp);
 
 	return (0);

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