From 39571e4eceeef9408be5ff772014803a167f8f2c Mon Sep 17 00:00:00 2001
From: avg <avg@FreeBSD.org>
Date: Wed, 13 Jul 2016 09:40:53 +0000
Subject: MFC r299902,299938: mount_snapshot: consolidate all error handling

---
 sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c | 38 ++++++++++++----------
 .../opensolaris/uts/common/fs/zfs/zfs_ctldir.c     |  1 +
 2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c b/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c
index 03e8e5f..6af1e8b 100644
--- a/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c
+++ b/sys/cddl/compat/opensolaris/kern/opensolaris_vfs.c
@@ -121,34 +121,39 @@ mount_snapshot(kthread_t *td, vnode_t **vpp, const char *fstype, char *fspath,
 	struct ucred *cr;
 	int error;
 
+	ASSERT_VOP_ELOCKED(*vpp, "mount_snapshot");
+
+	vp = *vpp;
+	*vpp = NULL;
+	error = 0;
+
 	/*
 	 * Be ultra-paranoid about making sure the type and fspath
 	 * variables will fit in our mp buffers, including the
 	 * terminating NUL.
 	 */
 	if (strlen(fstype) >= MFSNAMELEN || strlen(fspath) >= MNAMELEN)
-		return (ENAMETOOLONG);
-
-	vfsp = vfs_byname_kld(fstype, td, &error);
-	if (vfsp == NULL)
-		return (ENODEV);
-
-	vp = *vpp;
-	if (vp->v_type != VDIR)
-		return (ENOTDIR);
+		error = ENAMETOOLONG;
+	if (error == 0 && (vfsp = vfs_byname_kld(fstype, td, &error)) == NULL)
+		error = ENODEV;
+	if (error == 0 && vp->v_type != VDIR)
+		error = ENOTDIR;
 	/*
 	 * We need vnode lock to protect v_mountedhere and vnode interlock
 	 * to protect v_iflag.
 	 */
-	vn_lock(vp, LK_SHARED | LK_RETRY);
-	VI_LOCK(vp);
-	if ((vp->v_iflag & VI_MOUNT) != 0 || vp->v_mountedhere != NULL) {
+	if (error == 0) {
+		VI_LOCK(vp);
+		if ((vp->v_iflag & VI_MOUNT) == 0 && vp->v_mountedhere == NULL)
+			vp->v_iflag |= VI_MOUNT;
+		else
+			error = EBUSY;
 		VI_UNLOCK(vp);
-		VOP_UNLOCK(vp, 0);
-		return (EBUSY);
 	}
-	vp->v_iflag |= VI_MOUNT;
-	VI_UNLOCK(vp);
+	if (error != 0) {
+		vput(vp);
+		return (error);
+	}
 	VOP_UNLOCK(vp, 0);
 
 	/*
@@ -198,7 +203,6 @@ mount_snapshot(kthread_t *td, vnode_t **vpp, const char *fstype, char *fspath,
 		vfs_unbusy(mp);
 		vfs_freeopts(mp->mnt_optnew);
 		vfs_mount_destroy(mp);
-		*vpp = NULL;
 		return (error);
 	}
 
diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c
index a51e453..1c20aee 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_ctldir.c
@@ -1112,6 +1112,7 @@ domount:
 	(void) snprintf(mountpoint, mountpoint_len,
 	    "%s/" ZFS_CTLDIR_NAME "/snapshot/%s",
 	    dvp->v_vfsp->mnt_stat.f_mntonname, nm);
+	VERIFY0(vn_lock(*vpp, LK_EXCLUSIVE));
 	err = mount_snapshot(curthread, vpp, "zfs", mountpoint, snapname, 0);
 	kmem_free(mountpoint, mountpoint_len);
 	if (err == 0) {
-- 
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