From 64441fe62f7819a4437da90205aaf3227f83e35a Mon Sep 17 00:00:00 2001
From: dzogin <dzogin>
Date: Sat, 22 Aug 2009 16:07:33 +0000
Subject: [PATCH]  Branch b1_8  b=19566  i=oleg.drokin  i=nathan.rutman 
 Modified Files:   Tag: b1_8 	lustre/ChangeLog lustre/obdclass/obd_mount.c

Description: Prevent inconsistences between linux and lustre mount structures.
Details    : Wait indefinitely in server_wait_finished() until mnt_count drops.
	     Make the sleep interruptible.
---
 lustre/ChangeLog            |  6 ++++++
 lustre/obdclass/obd_mount.c | 48 ++++++++++++++++++++++++++++-----------------
 2 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/lustre/ChangeLog b/lustre/ChangeLog
index 3d46722..2fc3569 100644
--- a/lustre/ChangeLog
+++ b/lustre/ChangeLog
@@ -15,6 +15,12 @@ tbd Sun Microsystems, Inc.
 	  more information, please refer to bugzilla 17630.
 
 Severity   : normal
+Bugzilla   : 19566
+Description: Prevent inconsistences between linux and lustre mount structures.
+Details    : Wait indefinitely in server_wait_finished() until mnt_count drops.
+	     Make the sleep interruptible.
+
+Severity   : normal
 Bugzilla   : 20146
 Description: Increase of the size of the LDLM resource hash.
 Details    : Bump up RES_HASH_BITS=12.
diff --git a/lustre/obdclass/obd_mount.c b/lustre/obdclass/obd_mount.c
index 0bc3729..b573f13 100644
--- a/lustre/obdclass/obd_mount.c
+++ b/lustre/obdclass/obd_mount.c
@@ -1350,26 +1350,38 @@ out_free:
         RETURN(ERR_PTR(rc));
 }
 
+/* Wait here forever until the mount refcount is 0 before completing umount,
+ * else we risk dereferencing a null pointer.
+ * LNET may take e.g. 165s before killing zombies. 
+*/
 static void server_wait_finished(struct vfsmount *mnt)
 {
-        wait_queue_head_t   waitq;
-        struct l_wait_info  lwi;
-        int                 retries = 330;
-
-        init_waitqueue_head(&waitq);
-
-        while ((atomic_read(&mnt->mnt_count) > 1) && (retries > 0)) {
-                LCONSOLE_WARN("Mount still busy with %d refs, waiting for "
-                              "%d secs...\n",
-                              atomic_read(&mnt->mnt_count), retries);
-                /* Wait for a bit */
-                retries -= 5;
-                lwi = LWI_TIMEOUT(cfs_time_seconds(5), NULL, NULL);
-                l_wait_event(waitq, 0, &lwi);
-        }
-        if (atomic_read(&mnt->mnt_count) > 1) {
-                CERROR("Mount %p is still busy (%d refs), giving up.\n",
-                       mnt, atomic_read(&mnt->mnt_count));
+        cfs_waitq_t             waitq;
+        int                     rc, waited = 0;
+        cfs_sigset_t            blocked;
+
+        cfs_waitq_init(&waitq);
+
+        while (cfs_atomic_read(&mnt->mnt_count) > 1) {
+                if (waited && (waited % 30 == 0))
+                        LCONSOLE_WARN("Mount still busy with %d refs after "
+                                       "%d secs.\n",
+                                       atomic_read(&mnt->mnt_count),
+                                       waited);
+                /* Cannot use l_event_wait() for an interruptible sleep. */
+                waited += 3;
+                blocked = l_w_e_set_sigs(sigmask(SIGKILL)); 
+                rc = cfs_waitq_wait_event_interruptible_timeout(
+                        waitq, 
+                        (cfs_atomic_read(&mnt->mnt_count) == 1),
+                        cfs_time_seconds(3));
+                cfs_block_sigs(blocked);
+                if (rc < 0) {
+                        LCONSOLE_EMERG("Danger: interrupted umount %p with "
+                                       "%d refs!\n",
+                                       mnt, atomic_read(&mnt->mnt_count)); 
+                        break;
+                }
         }
 }
 
-- 
1.8.3.1