Commit ec30b461 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

blk-mq: don't change nr_hw_queues and nr_maps for kdump kernel 



For most of ARCHs, 'nr_cpus=1' is passed for kdump kernel, so
nr_hw_queues for each mapping is supposed to be 1 already.

More importantly, this way may cause trouble for driver, because blk-mq and
driver see different queue mapping since driver should setup hardware
queue setting before calling into allocating blk-mq tagset.

So not overriding nr_hw_queues and nr_maps for kdump kernel.

Cc: Wen Xiong <wenxiong@us.ibm.com>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240228040857.306483-1-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fb5d1d38

block/blk-mq.c

+6 −8
Original line number Diff line number Diff line
@@ -4379,7 +4379,7 @@ static void blk_mq_update_queue_map(struct blk_mq_tag_set *set) 
	if (set->nr_maps == 1)

		set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;



	if (set->ops->map_queues && !is_kdump_kernel()) {

	if (set->ops->map_queues) {

		int i;



		/*
@@ -4478,14 +4478,12 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set) 


	/*

	 * If a crashdump is active, then we are potentially in a very

	 * memory constrained environment. Limit us to 1 queue and

	 * 64 tags to prevent using too much memory.

	 * memory constrained environment. Limit us to  64 tags to prevent

	 * using too much memory.

	 */

	if (is_kdump_kernel()) {

		set->nr_hw_queues = 1;

		set->nr_maps = 1;

	if (is_kdump_kernel())

		set->queue_depth = min(64U, set->queue_depth);

	}



	/*

	 * There is no use for more h/w queues than cpus if we just have

	 * a single map
@@ -4515,7 +4513,7 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set) 
						  GFP_KERNEL, set->numa_node);

		if (!set->map[i].mq_map)

			goto out_free_mq_map;

		set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;

		set->map[i].nr_queues = set->nr_hw_queues;

	}



	blk_mq_update_queue_map(set);