[src/trunk]: src/sys/ufs/ffs Revert previous commit. Locking the snapshot vn...

[hannken <hannken%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/104da1b738a1
branches:  trunk
changeset: 764843:104da1b738a1
user:      hannken <hannken%NetBSD.org@localhost>
date:      Sun May 08 18:37:15 2011 +0000

description:
Revert previous commit.  Locking the snapshot vnode while the file system
is suspended extends the suspension until the vnode gets unlocked by
the caller of ffs_snapshot().

Resuming the file system before expunging all snapshots and syncing the
snapshot creates races and deadlocks with journaling file systems at least.

diffstat:

 sys/ufs/ffs/ffs_snapshot.c |  40 +++++++++++++---------------------------
 1 files changed, 13 insertions(+), 27 deletions(-)

diffs (76 lines):

diff -r 40b52ceca23c -r 104da1b738a1 sys/ufs/ffs/ffs_snapshot.c
--- a/sys/ufs/ffs/ffs_snapshot.c        Sun May 08 14:22:16 2011 +0000
+++ b/sys/ufs/ffs/ffs_snapshot.c        Sun May 08 18:37:15 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ffs_snapshot.c,v 1.114 2011/04/29 09:45:15 hannken Exp $       */
+/*     $NetBSD: ffs_snapshot.c,v 1.115 2011/05/08 18:37:15 hannken Exp $       */
 
 /*
  * Copyright 2000 Marshall Kirk McKusick. All Rights Reserved.
@@ -38,7 +38,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ffs_snapshot.c,v 1.114 2011/04/29 09:45:15 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ffs_snapshot.c,v 1.115 2011/05/08 18:37:15 hannken Exp $");
 
 #if defined(_KERNEL_OPT)
 #include "opt_ffs.h"
@@ -177,7 +177,7 @@
        return EOPNOTSUPP;
 }
 #else /* defined(FFS_NO_SNAPSHOT) */
-       bool suspended = false, snapshot_locked = false;
+       bool suspended = false;
        int error, redo = 0, snaploc;
        void *sbbuf = NULL;
        daddr_t *snaplist = NULL, snaplistsize = 0;
@@ -310,24 +310,6 @@
        DIP_ASSIGN(ip, mtimensec, ts.tv_nsec);
        ip->i_flag |= IN_CHANGE | IN_UPDATE;
        /*
-        * Lock the snapshot and resume file system.
-        */
-       mutex_enter(&si->si_snaplock);
-       mutex_enter(&si->si_lock);
-       si->si_owner = curlwp;
-       mutex_exit(&si->si_lock);
-       snapshot_locked = true;
-       KASSERT(suspended);
-       vfs_resume(vp->v_mount);
-       suspended = false;
-#ifdef DEBUG
-       getmicrotime(&endtime);
-       timersub(&endtime, &starttime, &endtime);
-       printf("%s: suspended %lld.%03d sec, redo %d of %d\n",
-           mp->mnt_stat.f_mntonname, (long long)endtime.tv_sec,
-           endtime.tv_usec / 1000, redo, fs->fs_ncg);
-#endif
-       /*
         * Copy allocation information from all snapshots and then
         * expunge them from our view.
         */
@@ -399,13 +381,17 @@
        si->si_gen++;
        mutex_exit(&si->si_lock);
 
-       if (suspended)
+       if (suspended) {
+               VOP_UNLOCK(vp);
                vfs_resume(vp->v_mount);
-       if (snapshot_locked) {
-               mutex_enter(&si->si_lock);
-               si->si_owner = NULL;
-               mutex_exit(&si->si_lock);
-               mutex_exit(&si->si_snaplock);
+               vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+#ifdef DEBUG
+               getmicrotime(&endtime);
+               timersub(&endtime, &starttime, &endtime);
+               printf("%s: suspended %lld.%03d sec, redo %d of %d\n",
+                   mp->mnt_stat.f_mntonname, (long long)endtime.tv_sec,
+                   endtime.tv_usec / 1000, redo, fs->fs_ncg);
+#endif
        }
        if (error) {
                if (!UFS_WAPBL_BEGIN(mp)) {