svn commit: r345376 - head/sys/fs/nullfs

[Konstantin Belousov]

Author: kib
Date: Thu Mar 21 13:30:48 2019
New Revision: 345376
URL: https://svnweb.freebsd.org/changeset/base/345376

Log:
  nullfs: fix unmounts when filesystem is active.
  
  If vflush() did not completely flushed the mount vnodes queue, either
  retry for forced unmounts, or give up for non-forced.  This situation
  can occur when new vnodes are instantiated while vflush() worked.
  
  Reported and tested by:	pho
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week

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

Modified: head/sys/fs/nullfs/null_vfsops.c
==============================================================================
--- head/sys/fs/nullfs/null_vfsops.c	Thu Mar 21 11:32:52 2019	(r345375)
+++ head/sys/fs/nullfs/null_vfsops.c	Thu Mar 21 13:30:48 2019	(r345376)
@@ -235,7 +235,7 @@ nullfs_unmount(mp, mntflags)
 {
 	struct null_mount *mntdata;
 	struct mount *ump;
-	int error, flags;
+	int error, flags, rootrefs;
 
 	NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
 
@@ -244,10 +244,20 @@ nullfs_unmount(mp, mntflags)
 	else
 		flags = 0;
 
-	/* There is 1 extra root vnode reference (nullm_rootvp). */
-	error = vflush(mp, 1, flags, curthread);
-	if (error)
-		return (error);
+	for (rootrefs = 1;; rootrefs = 0) {
+		/* There is 1 extra root vnode reference (nullm_rootvp). */
+		error = vflush(mp, rootrefs, flags, curthread);
+		if (error)
+			return (error);
+		MNT_ILOCK(mp);
+		if (mp->mnt_nvnodelistsize == 0) {
+			MNT_IUNLOCK(mp);
+			break;
+		}
+		MNT_IUNLOCK(mp);
+		if ((mntflags & MNT_FORCE) == 0)
+			return (EBUSY);
+	}
 
 	/*
 	 * Finally, throw away the null_mount structure