Re: [PATCH 0/5] nvme-fabrics: fix connects with isolated CPUs and queue mapping bugs

[Keith Busch]

On Wed, Oct 14, 2026 at 09:46:38AM +0200, Daniel Wagner wrote:
> Connecting a fabrics controller fails when all CPUs of a hardware
> context are isolated with isolcpus=domain or an isolated cpuset
> partition. Since commit a46c27026da1 ("blk-mq: don't schedule block
> kworker on isolated CPUs") the CPU mask of such a hardware context is
> empty and blk_mq_alloc_request_hctx() fails the Connect command with
> -EXDEV. Patch 2 lets passthrough requests use the software context of a
> housekeeping CPU instead.
> 
> Patches 3-5 fix the fabrics queue mapping:
> 
>   - Stale io_queues[] entries after a reconnect with fewer queues crash
>     blk_mq_map_swqueue().
>   - A queue type can get more queues than online CPUs, so connecting
>     fails with -EXDEV.
>   - Without queues left for polling, the queue claims poll support and
>     polled I/O ends up on a non-poll queue.
> 
> Patch 1 fixes a regression in nvme-7.4 found while testing: since commit
> 61b0ed3be81b ("nvme-tcp: parallelize I/O queue allocation and startup")
> nvme_tcp_init_request takes a mutex before it is initialized, which
> disables lock debugging on the first connect.

It seems the nvme patches (1, 3-5) can be applied independently of the
blk-mq patch, so I staged those in nvme-7.4.