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From: Jens Axboe <axboe@kernel.dk>
To: linux-mm <linux-mm@kvack.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>
Subject: [PATCH] mm: fix polled swap page in
Date: Wed, 5 Dec 2018 06:49:08 -0700
Message-ID: <e15243a8-2cdf-c32c-ecee-f289377c8ef9@kernel.dk> (raw)

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.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

diff --git a/mm/page_io.c b/mm/page_io.c
index 5bdfd21c1bd9..f3455f9f8dc7 100644
--- a/mm/page_io.c
+++ b/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);
@@ -411,7 +413,7 @@ 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);

-- 
Jens Axboe

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