block: Relax a check in blk_start_queue()

Calling blk_start_queue() from interrupt context with the queue
lock held and without disabling IRQs, as the skd driver does, is
safe. This patch avoids that loading the skd driver triggers the
following warning:

WARNING: CPU: 11 PID: 1348 at block/blk-core.c:283 blk_start_queue+0x84/0xa0
RIP: 0010:blk_start_queue+0x84/0xa0
Call Trace:
 skd_unquiesce_dev+0x12a/0x1d0 [skd]
 skd_complete_internal+0x1e7/0x5a0 [skd]
 skd_complete_other+0xc2/0xd0 [skd]
 skd_isr_completion_posted.isra.30+0x2a5/0x470 [skd]
 skd_isr+0x14f/0x180 [skd]
 irq_forced_thread_fn+0x2a/0x70
 irq_thread+0x144/0x1a0
 kthread+0x125/0x140
 ret_from_fork+0x2a/0x40

Fixes: commit a038e25 ("[PATCH] blk_start_queue() must be called with irq disabled - add warning")
Signed-off-by: Bart Van Assche <[email protected]>
Cc: Paolo 'Blaisorblade' Giarrusso <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Hannes Reinecke <[email protected]>
Cc: Johannes Thumshirn <[email protected]>
Cc: <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

block/blk-core.c

@@ -280,7 +280,7 @@ EXPORT_SYMBOL(blk_start_queue_async);
 void blk_start_queue(struct request_queue *q)
 {
 	lockdep_assert_held(q->queue_lock);
-	WARN_ON(!irqs_disabled());
+	WARN_ON(!in_interrupt() && !irqs_disabled());
 	WARN_ON_ONCE(q->mq_ops);
 
 	queue_flag_clear(QUEUE_FLAG_STOPPED, q);