[PATCH 4/5] nvme-fabrics: limit each queue type to the number of online CPUs

[Hannes Reinecke]

On 10/14/26 9:46 AM, Daniel Wagner wrote:
> From: Daniel Wagner <wagi at kernel.org>
> 
> nvmf_nr_io_queues limits each queue type to the number of online CPUs
> when asking for I/O queues, but nvmf_set_io_queues hands out the
> granted queues without these limits, and only nr_io_queues is clamped
> when parsing the options.
> 
> E.g. with 2 CPUs, nr_io_queues=2, nr_write_queues=10 and
> nr_poll_queues=10, 2 + 2 + 2 = 6 queues are requested, but handed out
> as 4 default, 2 read and 0 poll queues.  blk_mq_map_queues can't create
> more CPU masks than there are CPUs, so default queues 2 and 3 take over
> the CPUs of default queues 0 and 1, and connecting the I/O queue of
> default queue 1 fails with -EXDEV.
> 
> Apply the same limits in nvmf_set_io_queues.  A queue type with more
> queues than online CPUs always has a hardware context without an online
> CPU, so no working setup changes.  The options are not modified, so the
> limits follow CPU hotplug on reconnect.
> 
> Fixes: 6486199378a5 ("nvme-tcp: fix queue mapping when queue count is limited")
> Fixes: a249d3066de6 ("nvme-fabrics: add queue setup helpers")
> Signed-off-by: Daniel Wagner <wagi at kernel.org>
> ---
>   drivers/nvme/host/fabrics.c | 21 +++++++++++++++------
>   1 file changed, 15 insertions(+), 6 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare at kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare at suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich