[3.16.y-ckt stable] Patch "ocfs2: dlm: fix race between purge and get lock resource" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Wed May 20 12:31:19 UTC 2015
This is a note to let you know that I have just added a patch titled
ocfs2: dlm: fix race between purge and get lock resource
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt12.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From f346335dd059d3c253548b55895b6ebf559a1c81 Mon Sep 17 00:00:00 2001
From: Junxiao Bi <junxiao.bi at oracle.com>
Date: Tue, 5 May 2015 16:24:02 -0700
Subject: ocfs2: dlm: fix race between purge and get lock resource
commit b1432a2a35565f538586774a03bf277c27fc267d upstream.
There is a race window in dlm_get_lock_resource(), which may return a
lock resource which has been purged. This will cause the process to
hang forever in dlmlock() as the ast msg can't be handled due to its
lock resource not existing.
dlm_get_lock_resource {
...
spin_lock(&dlm->spinlock);
tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash);
if (tmpres) {
spin_unlock(&dlm->spinlock);
>>>>>>>> race window, dlm_run_purge_list() may run and purge
the lock resource
spin_lock(&tmpres->spinlock);
...
spin_unlock(&tmpres->spinlock);
}
}
Signed-off-by: Junxiao Bi <junxiao.bi at oracle.com>
Cc: Joseph Qi <joseph.qi at huawei.com>
Cc: Mark Fasheh <mfasheh at suse.com>
Cc: Joel Becker <jlbec at evilplan.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 9d405d6d2504..7b9f96899812 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -768,6 +768,19 @@ lookup:
if (tmpres) {
spin_unlock(&dlm->spinlock);
spin_lock(&tmpres->spinlock);
+
+ /*
+ * Right after dlm spinlock was released, dlm_thread could have
+ * purged the lockres. Check if lockres got unhashed. If so
+ * start over.
+ */
+ if (hlist_unhashed(&tmpres->hash_node)) {
+ spin_unlock(&tmpres->spinlock);
+ dlm_lockres_put(tmpres);
+ tmpres = NULL;
+ goto lookup;
+ }
+
/* Wait on the thread that is mastering the resource */
if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) {
__dlm_wait_on_lockres(tmpres);
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