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

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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: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2017-08-04 13:37:03 -06:00
parent 62d20aa6a0
commit 7f5562d5ec
1 changed files with 13 additions and 3 deletions
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16
block/blk-mq-tag.c
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@ -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];
iter_data->fn(rq, iter_data->data, reserved);
/*
* 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;
}