Re: [PATCH 4/5] nvme-fabrics: limit each queue type to the number of online CPUs
From: Hannes Reinecke
Date: Wed Oct 21 2026 - 07:12:32 EST
On 10/14/26 9:46 AM, Daniel Wagner wrote:
From: Daniel Wagner <wagi@xxxxxxxxxx>Reviewed-by: Hannes Reinecke <hare@xxxxxxxxxx>
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@xxxxxxxxxx>
---
drivers/nvme/host/fabrics.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
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