@@ -86,6 +86,7 @@ struct multipath {
unsigned queue_if_no_path:1; /* Queue I/O if last path fails? */
unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
unsigned retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
+ unsigned pg_init_disabled:1; /* pg_init is not currently allowed */
unsigned pg_init_retries; /* Number of times to retry pg_init */
unsigned pg_init_count; /* Number of times pg_init called */
@@ -497,7 +498,8 @@ static void process_queued_ios(struct work_struct *work)
(!pgpath && !m->queue_if_no_path))
must_queue = 0;
- if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
+ if (m->pg_init_required && !m->pg_init_in_progress && pgpath &&
+ !m->pg_init_disabled)
__pg_init_all_paths(m);
spin_unlock_irqrestore(&m->lock, flags);
@@ -941,10 +943,20 @@ static void multipath_wait_for_pg_init_completion(struct multipath *m)
static void flush_multipath_work(struct multipath *m)
{
+ unsigned long flags;
+
+ spin_lock_irqsave(&m->lock, flags);
+ m->pg_init_disabled = 1;
+ spin_unlock_irqrestore(&m->lock, flags);
+
flush_workqueue(kmpath_handlerd);
multipath_wait_for_pg_init_completion(m);
flush_workqueue(kmultipathd);
flush_work(&m->trigger_event);
+
+ spin_lock_irqsave(&m->lock, flags);
+ m->pg_init_disabled = 0;
+ spin_unlock_irqrestore(&m->lock, flags);
}
static void multipath_dtr(struct dm_target *ti)
@@ -1163,7 +1175,7 @@ static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
spin_lock_irqsave(&m->lock, flags);
- if (m->pg_init_count <= m->pg_init_retries)
+ if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
m->pg_init_required = 1;
else
limit_reached = 1;
@@ -1689,7 +1701,7 @@ out:
*---------------------------------------------------------------*/
static struct target_type multipath_target = {
.name = "multipath",
- .version = {1, 5, 1},
+ .version = {1, 6, 0},
.module = THIS_MODULE,
.ctr = multipath_ctr,
.dtr = multipath_dtr,
This is a note to let you know that I have just added a patch titled dm mpath: fix race condition between multipath_dtr and pg_init_done to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.14. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 1b5a93ad352aceaeee02607bd438a8847ce02637 Mon Sep 17 00:00:00 2001 From: Shiva Krishna Merla <shivakrishna.merla@netapp.com> Date: Wed, 30 Oct 2013 03:26:38 +0000 Subject: dm mpath: fix race condition between multipath_dtr and pg_init_done commit 954a73d5d3073df2231820c718fdd2f18b0fe4c9 upstream. Whenever multipath_dtr() is happening we must prevent queueing any further path activation work. Implement this by adding a new 'pg_init_disabled' flag to the multipath structure that denotes future path activation work should be skipped if it is set. By disabling pg_init and then re-enabling in flush_multipath_work() we also avoid the potential for pg_init to be initiated while suspending an mpath device. Without this patch a race condition exists that may result in a kernel panic: 1) If after pg_init_done() decrements pg_init_in_progress to 0, a call to wait_for_pg_init_completion() assumes there are no more pending path management commands. 2) If pg_init_required is set by pg_init_done(), due to retryable mode_select errors, then process_queued_ios() will again queue the path activation work. 3) If free_multipath() completes before activate_path() work is called a NULL pointer dereference like the following can be seen when accessing members of the recently destructed multipath: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 RIP: 0010:[<ffffffffa003db1b>] [<ffffffffa003db1b>] activate_path+0x1b/0x30 [dm_multipath] [<ffffffff81090ac0>] worker_thread+0x170/0x2a0 [<ffffffff81096c80>] ? autoremove_wake_function+0x0/0x40 [switch to disabling pg_init in flush_multipath_work & header edits by Mike Snitzer] Signed-off-by: Shiva Krishna Merla <shivakrishna.merla@netapp.com> Reviewed-by: Krishnasamy Somasundaram <somasundaram.krishnasamy@netapp.com> Tested-by: Speagle Andy <Andy.Speagle@netapp.com> Acked-by: Junichi Nomura <j-nomura@ce.jp.nec.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/md/dm-mpath.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) -- 1.8.3.2