Fixed rev.1.81. mp->mnt_kern_flag was restored in the non-error case of

`mount -u'.  This only matters for `mount -u' competing with unmounts.
If I understand the locking correctly: if mount() blocks, then unmount()
may run and set mp->kern_flag for the same mp.  Then unmount() blocks
waiting for mount() to finish.  When unmount() continues, its MNTK flags
(MNTK_UNMOUNT and MNTK_MWAIT) may have been clobbered.

Didn't fix old bugs:
- restoring mp->mnt_kern_flag is wrong for the same reasons in the error
  case.
- the error case of unmount() seems to be broken too:
  (a) MNTK_UNMOUNT gets clobbered, although another unmount() may have
      set it.  Perhaps it shouldn't be set until after the full lock is
      aquired.
  (b) MNTK_MWAIT isn't honoured.

Fixed a nearby style bug.

1 files changed, 4 insertions, 3 deletions

diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index eb8cb4e..8a0ab1d 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)vfs_syscalls.c	8.13 (Berkeley) 4/15/94
- * $Id: vfs_syscalls.c,v 1.81 1997/11/12 05:42:17 julian Exp $
+ * $Id: vfs_syscalls.c,v 1.82 1997/11/13 00:28:50 julian Exp $
  */
 
 /*
@@ -274,10 +274,11 @@ update:
 		if (mp->mnt_kern_flag & MNTK_WANTRDWR)
 			mp->mnt_flag &= ~MNT_RDONLY;
 		mp->mnt_flag &=~ (MNT_UPDATE | MNT_RELOAD | MNT_FORCE);
-		mp->mnt_kern_flag &=~ (MNTK_WANTRDWR);
-		if (error)
+		mp->mnt_kern_flag &=~ MNTK_WANTRDWR;
+		if (error) {
 			mp->mnt_flag = flag;
 			mp->mnt_kern_flag = flag2;
+		}
 		vfs_unbusy(mp, p);
 		return (error);
 	}