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Commit 7f5562d5 authored by Jens Axboe's avatar Jens Axboe
Browse files

blk-mq-tag: check for NULL rq when iterating tags 



Since we introduced blk-mq-sched, the tags->rqs[] array has been
dynamically assigned. So we need to check for NULL when iterating,
since there's a window of time where the bit is set, but we haven't
dynamically assigned the tags->rqs[] array position yet.

This is perfectly safe, since the memory backing of the request is
never going away while the device is alive.

Reviewed-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 62d20aa6

block/blk-mq-tag.c

+12 −2
Original line number Diff line number Diff line
@@ -214,7 +214,11 @@ static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) 
		bitnr += tags->nr_reserved_tags;

	rq = tags->rqs[bitnr];



	if (rq->q == hctx->queue)

	/*

	 * We can hit rq == NULL here, because the tagging functions

	 * test and set the bit before assining ->rqs[].

	 */

	if (rq && rq->q == hctx->queue)

		iter_data->fn(hctx, rq, iter_data->data, reserved);

	return true;

}
@@ -248,9 +252,15 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) 


	if (!reserved)

		bitnr += tags->nr_reserved_tags;

	rq = tags->rqs[bitnr];



	/*

	 * We can hit rq == NULL here, because the tagging functions

	 * test and set the bit before assining ->rqs[].

	 */

	rq = tags->rqs[bitnr];

	if (rq)

		iter_data->fn(rq, iter_data->data, reserved);



	return true;

}