ocfs2: use spinlock irqsave for downconvert lock.patch

When ocfs2dc thread holds dc_task_lock spinlock and receives soft IRQ it
deadlock itself trying to get same spinlock in ocfs2_wake_downconvert_thread.
Below is the stack snippet.

The patch disables interrupts when acquiring dc_task_lock spinlock.

	ocfs2_wake_downconvert_thread
	ocfs2_rw_unlock
	ocfs2_dio_end_io
	dio_complete
	.....
	bio_endio
	req_bio_endio
	....
	scsi_io_completion
	blk_done_softirq
	__do_softirq
	do_softirq
	irq_exit
	do_IRQ
	ocfs2_downconvert_thread
	[kthread]

Signed-off-by: Srinivas Eeda <srinivas.eeda@oracle.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 274529cce9c61354309ff91b1ccc3c183b817573..4f7795fb5fc0b78a6f58d28f2de69356ff5e197d 100644 (file)
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -3932,6 +3932,8 @@ unqueue:
 static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
                                        struct ocfs2_lock_res *lockres)
 {
+       unsigned long flags;
+
        assert_spin_locked(&lockres->l_lock);
 
        if (lockres->l_flags & OCFS2_LOCK_FREEING) {
@@ -3945,21 +3947,22 @@ static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
 
        lockres_or_flags(lockres, OCFS2_LOCK_QUEUED);
 
-       spin_lock(&osb->dc_task_lock);
+       spin_lock_irqsave(&osb->dc_task_lock, flags);
        if (list_empty(&lockres->l_blocked_list)) {
                list_add_tail(&lockres->l_blocked_list,
                              &osb->blocked_lock_list);
                osb->blocked_lock_count++;
        }
-       spin_unlock(&osb->dc_task_lock);
+       spin_unlock_irqrestore(&osb->dc_task_lock, flags);
 }
 
 static void ocfs2_downconvert_thread_do_work(struct ocfs2_super *osb)
 {
        unsigned long processed;
+       unsigned long flags;
        struct ocfs2_lock_res *lockres;
 
-       spin_lock(&osb->dc_task_lock);
+       spin_lock_irqsave(&osb->dc_task_lock, flags);
        /* grab this early so we know to try again if a state change and
         * wake happens part-way through our work  */
        osb->dc_work_sequence = osb->dc_wake_sequence;
@@ -3972,38 +3975,40 @@ static void ocfs2_downconvert_thread_do_work(struct ocfs2_super *osb)
                                     struct ocfs2_lock_res, l_blocked_list);
                list_del_init(&lockres->l_blocked_list);
                osb->blocked_lock_count--;
-               spin_unlock(&osb->dc_task_lock);
+               spin_unlock_irqrestore(&osb->dc_task_lock, flags);
 
                BUG_ON(!processed);
                processed--;
 
                ocfs2_process_blocked_lock(osb, lockres);
 
-               spin_lock(&osb->dc_task_lock);
+               spin_lock_irqsave(&osb->dc_task_lock, flags);
        }
-       spin_unlock(&osb->dc_task_lock);
+       spin_unlock_irqrestore(&osb->dc_task_lock, flags);
 }
 
 static int ocfs2_downconvert_thread_lists_empty(struct ocfs2_super *osb)
 {
        int empty = 0;
+       unsigned long flags;
 
-       spin_lock(&osb->dc_task_lock);
+       spin_lock_irqsave(&osb->dc_task_lock, flags);
        if (list_empty(&osb->blocked_lock_list))
                empty = 1;
 
-       spin_unlock(&osb->dc_task_lock);
+       spin_unlock_irqrestore(&osb->dc_task_lock, flags);
        return empty;
 }
 
 static int ocfs2_downconvert_thread_should_wake(struct ocfs2_super *osb)
 {
        int should_wake = 0;
+       unsigned long flags;
 
-       spin_lock(&osb->dc_task_lock);
+       spin_lock_irqsave(&osb->dc_task_lock, flags);
        if (osb->dc_work_sequence != osb->dc_wake_sequence)
                should_wake = 1;
-       spin_unlock(&osb->dc_task_lock);
+       spin_unlock_irqrestore(&osb->dc_task_lock, flags);
 
        return should_wake;
 }
@@ -4033,10 +4038,12 @@ static int ocfs2_downconvert_thread(void *arg)
 
 void ocfs2_wake_downconvert_thread(struct ocfs2_super *osb)
 {
-       spin_lock(&osb->dc_task_lock);
+       unsigned long flags;
+
+       spin_lock_irqsave(&osb->dc_task_lock, flags);
        /* make sure the voting thread gets a swipe at whatever changes
         * the caller may have made to the voting state */
        osb->dc_wake_sequence++;
-       spin_unlock(&osb->dc_task_lock);
+       spin_unlock_irqrestore(&osb->dc_task_lock, flags);
        wake_up(&osb->dc_event);
 }