On 7/20/25 13:35, Nilay Shroff wrote:
When setting up a null block device, we initialize a tagset that
includes a driver_data field—typically used by block drivers to
store a pointer to driver-specific data. In the case of null_blk,
this should point to the struct nullb instance.
However, due to recent tagset refactoring in the null_blk driver, we
missed initializing driver_data when creating a shared tagset. As a
result, software queues (ctx) fail to map correctly to new hardware
queues (hctx). For example, increasing the number of submit queues
triggers an nr_hw_queues update, which invokes null_map_queues() to
remap queues. Since set->driver_data is unset, null_map_queues()
fails to map any ctx to the new hctxs, leading to hctx->nr_ctx == 0,
effectively making the hardware queues unusable for I/O.
This patch fixes the issue by ensuring that set->driver_data is properly
initialized to point to the struct nullb during tagset setup.
Fixes: 72ca28765fc4 ("null_blk: refactor tag_set setup")
Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
---
drivers/block/null_blk/main.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index aa163ae9b2aa..9e1c4ce6fc42 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1854,13 +1854,14 @@ static int null_init_global_tag_set(void)
static int null_setup_tagset(struct nullb *nullb)
{
+ nullb->tag_set->driver_data = nullb;
+
if (nullb->dev->shared_tags) {
nullb->tag_set = &tag_set;
return null_init_global_tag_set();
}
nullb->tag_set = &nullb->__tag_set;
- nullb->tag_set->driver_data = nullb;
nullb->tag_set->nr_hw_queues = nullb->dev->submit_queues;
nullb->tag_set->queue_depth = nullb->dev->hw_queue_depth;
nullb->tag_set->numa_node = nullb->dev->home_node;
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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