On 09/09/2014 06:18 PM, Robert Elliott wrote:
> From: Robert Elliott <[email protected]>
>
> Make blk_mq_alloc_tag_set return an error if set->reserved_tags
> is greater than BLK_MQ_MAX_DEPTH minus the minimum number of
> tags, since:
> * set->queue_depth is truncated to that value
> * set->reserved_tags needs to be less than set->queue_depth
>
> Signed-off-by: Robert Elliott <[email protected]>
> ---
> block/blk-mq.c | 8 +++++---
> 1 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index c49fe00..dc2970d 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1936,16 +1936,18 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
> return -EINVAL;
> if (!set->queue_depth)
> return -EINVAL;
> + if (set->reserved_tags > BLK_MQ_MAX_DEPTH - BLK_MQ_TAG_MIN)
> + return -EINVAL;
> if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
> return -EINVAL;
>
> if (!set->nr_hw_queues || !set->ops->queue_rq || !set->ops->map_queue)
> return -EINVAL;
>
> - if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
> + if (set->queue_depth > BLK_MQ_MAX_DEPTH - set->reserved_tags) {
This is harder to read than:
if (set->queue_depth + set->reserved_tags > BLK_MQ_MAX_DEPTH) {
which more clearly expresses the same thing. But set->queue_depth is the
total pool, reserved tags come out of that pool. So I don't think this
is correct.
--
Jens Axboe
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