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: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240228040857.306483-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 7111bd4180e792cf705f062cfe48b797d86ed6b8..b7ba91d53c41600ecdf7851788930d2d1e743510 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -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);