Two fixes for md

1/ Another live lock, needs backporting
 2/ work-around false positive with new warnings.
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Merge tag 'md/3.19-fixes' of git://neil.brown.name/md

Pull two fixes for md from Neil Brown:

 - Another live lock, needs backporting

 - work-around false positive with new warnings.

* tag 'md/3.19-fixes' of git://neil.brown.name/md:
  md/bitmap: fix a might_sleep() warning.
  md/raid5: fix another livelock caused by non-aligned writes.

drivers/md/bitmap.c

@@ -72,6 +72,19 @@ __acquires(bitmap->lock)
 	/* this page has not been allocated yet */
 
 	spin_unlock_irq(&bitmap->lock);
+	/* It is possible that this is being called inside a
+	 * prepare_to_wait/finish_wait loop from raid5c:make_request().
+	 * In general it is not permitted to sleep in that context as it
+	 * can cause the loop to spin freely.
+	 * That doesn't apply here as we can only reach this point
+	 * once with any loop.
+	 * When this function completes, either bp[page].map or
+	 * bp[page].hijacked.  In either case, this function will
+	 * abort before getting to this point again.  So there is
+	 * no risk of a free-spin, and so it is safe to assert
+	 * that sleeping here is allowed.
+	 */
+	sched_annotate_sleep();
 	mappage = kzalloc(PAGE_SIZE, GFP_NOIO);
 	spin_lock_irq(&bitmap->lock);
 

drivers/md/raid5.c

@@ -3195,6 +3195,11 @@ static void handle_stripe_dirtying(struct r5conf *conf,
 					  (unsigned long long)sh->sector,
 					  rcw, qread, test_bit(STRIPE_DELAYED, &sh->state));
 	}
+
+	if (rcw > disks && rmw > disks &&
+	    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		set_bit(STRIPE_DELAYED, &sh->state);
+
 	/* now if nothing is locked, and if we have enough data,
 	 * we can start a write request
 	 */