linux-kernel - [RFC PATCH bitmap-for-next 0/4] lib/cpumask, blk_mq: Fix blk_mq_hctx_next_cpu() vs cpumask

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Date:   Thu,  6 Oct 2022 13:21:08 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>, Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [RFC PATCH bitmap-for-next 0/4] lib/cpumask, blk_mq: Fix blk_mq_hctx_next_cpu() vs cpumask_check()

Hi,

I've split this from [1] given I don't have any updates to the other patches,
and this can live separately from them.

I figured I'd follow what Yury has done and condense the logic of
cpumask_next_wrap() into a macro, however cpumask_next_wrap() has a UP variant
which makes this a bit more annoying.

I've tried giving the UP variant its own macro in cpumask.c and declaring
it there, but that means making cpumask.c compile under !CONFIG_SMP (again),
which means doing the same for all of the cpumask.c functions that have UP
variants (cpumask_local_spread(), cpumask_any_*distribute()...).

Before going too deep in what might be a stupid idea, I thought I'd stop there,
send what I have, and check what folks if that sounds sane.

If it does, I see two ways of handling the UP stubs:
o Get rid of the UP optimizations and use the same code as SMP
o Move *all* definitions of the UP optimizations into cpumask.c with
  a different set of macros (e.g. a *_UP() variant).

[1]: http://lore.kernel.org/r/20221003153420.285896-1-vschneid@redhat.com

Cheers,
Valentin

Valentin Schneider (4):
  lib/cpumask: Generate cpumask_next_wrap() body with a macro
  lib/cpumask: Fix cpumask_check() warning in cpumask_next_wrap*()
  lib/cpumask: Introduce cpumask_next_and_wrap()
  blk_mq: Fix cpumask_check() warning in blk_mq_hctx_next_cpu()

 block/blk-mq.c          | 39 +++++++++------------------
 include/linux/cpumask.h | 22 +++++++++++++++
 lib/cpumask.c           | 60 ++++++++++++++++++++++++++++++-----------
 3 files changed, 79 insertions(+), 42 deletions(-)

--
2.31.1