mm/page_io.c: fix polled swap page in

swap_readpage() wants to do polling to bring in pages if asked to, but
it doesn't mark the bio as being polled.  Additionally, the looping
around the blk_poll() check isn't correct - if we get a zero return, we
should call io_schedule(), we can't just assume that the bio has
completed.  The regular bio->bi_private check should be used for that.

Link: http://lkml.kernel.org/r/e15243a8-2cdf-c32c-ecee-f289377c8ef9@kernel.dkSigned-off-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_io.c

@@ -401,6 +401,8 @@ int swap_readpage(struct page *page, bool synchronous)
 	get_task_struct(current);
 	bio->bi_private = current;
 	bio_set_op_attrs(bio, REQ_OP_READ, 0);
+	if (synchronous)
+		bio->bi_opf |= REQ_HIPRI;
 	count_vm_event(PSWPIN);
 	bio_get(bio);
 	qc = submit_bio(bio);
@@ -410,7 +412,7 @@ int swap_readpage(struct page *page, bool synchronous)
 			break;
 
 		if (!blk_poll(disk->queue, qc, true))
-			break;
+			io_schedule();
 	}
 	__set_current_state(TASK_RUNNING);
 	bio_put(bio);