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>

1 files changed, 19 insertions, 12 deletions

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 274529cce9c..4f7795fb5fc 100644
--- 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);
 }