svn commit: r342820 - stable/12/sys/kern

[Kirk McKusick]

Author: mckusick
Date: Sun Jan  6 22:48:56 2019
New Revision: 342820
URL: https://svnweb.freebsd.org/changeset/base/342820

Log:
  MFC of 342135 and 342290
  
  Properly respond to error from VFS_ROOT() during mount.
  
  Sponsored by: Netflix

Modified:
  stable/12/sys/kern/vfs_mount.c
Directory Properties:
  stable/12/   (props changed)

Modified: stable/12/sys/kern/vfs_mount.c
==============================================================================
--- stable/12/sys/kern/vfs_mount.c	Sun Jan  6 22:34:47 2019	(r342819)
+++ stable/12/sys/kern/vfs_mount.c	Sun Jan  6 22:48:56 2019	(r342820)
@@ -837,7 +837,7 @@ vfs_domount_first(
 	struct vattr va;
 	struct mount *mp;
 	struct vnode *newdp;
-	int error;
+	int error, error1;
 
 	ASSERT_VOP_ELOCKED(vp, __func__);
 	KASSERT((fsflags & MNT_UPDATE) == 0, ("MNT_UPDATE shouldn't be here"));
@@ -889,8 +889,15 @@ vfs_domount_first(
 	 * XXX The final recipients of VFS_MOUNT just overwrite the ndp they
 	 * get.  No freeing of cn_pnbuf.
 	 */
-	error = VFS_MOUNT(mp);
-	if (error != 0) {
+	error1 = 0;
+	if ((error = VFS_MOUNT(mp)) != 0 ||
+	    (error1 = VFS_STATFS(mp, &mp->mnt_stat)) != 0 ||
+	    (error1 = VFS_ROOT(mp, LK_EXCLUSIVE, &newdp)) != 0) {
+		if (error1 != 0) {
+			error = error1;
+			if ((error1 = VFS_UNMOUNT(mp, 0)) != 0)
+				printf("VFS_UNMOUNT returned %d\n", error1);
+		}
 		vfs_unbusy(mp);
 		mp->mnt_vnodecovered = NULL;
 		vfs_mount_destroy(mp);
@@ -900,12 +907,12 @@ vfs_domount_first(
 		vrele(vp);
 		return (error);
 	}
+	VOP_UNLOCK(newdp, 0);
 
 	if (mp->mnt_opt != NULL)
 		vfs_freeopts(mp->mnt_opt);
 	mp->mnt_opt = mp->mnt_optnew;
 	*optlist = NULL;
-	(void)VFS_STATFS(mp, &mp->mnt_stat);
 
 	/*
 	 * Prevent external consumers of mount options from reading mnt_optnew.
@@ -931,8 +938,7 @@ vfs_domount_first(
 	TAILQ_INSERT_TAIL(&mountlist, mp, mnt_list);
 	mtx_unlock(&mountlist_mtx);
 	vfs_event_signal(NULL, VQ_MOUNT, 0);
-	if (VFS_ROOT(mp, LK_EXCLUSIVE, &newdp))
-		panic("mount: lost mount");
+	vn_lock(newdp, LK_EXCLUSIVE | LK_RETRY);
 	VOP_UNLOCK(vp, 0);
 	EVENTHANDLER_DIRECT_INVOKE(vfs_mounted, mp, newdp, td);
 	VOP_UNLOCK(newdp, 0);