Re: [PATCH v2 00/13] cpumask: cleanup cpumask_next_wrap() implementation and usage

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jan 28, 2025 at 11:46:29AM -0500, Yury Norov wrote:
> cpumask_next_wrap() is overly complicated, comparing to it's generic
> version find_next_bit_wrap(), not mentioning it duplicates the above.
> It roots to the times when the function was used in the implementation
> of for_each_cpu_wrap() iterator. The function has 2 additional parameters
> that were used to catch loop termination condition for the iterator.
> (Although, only one is needed.)
> 
> Since 4fe49b3b97c262 ("lib/bitmap: introduce for_each_set_bit_wrap()
> macro"), for_each_cpu_wrap() is wired to corresponding generic
> wrapping bitmap iterator, and additional complexity of
> cpumask_next_wrap() is not needed anymore.
> 
> All existing users call cpumask_next_wrap() in a manner that makes
> it possible to turn it to a straight and simple alias to
> find_next_bit_wrap().
> 
> This series replaces historical 4-parameter cpumask_next_wrap() with a
> thin 2-parameter wrapper around find_next_bit_wrap().
> 
> Where it's possible to use for_each_cpu_wrap() iterator, the code is
> switched to use it because it's always preferable to use iterators over
> open loops.
> 
> This series touches various scattered subsystems and To-list for the
> whole series is quite a long. To minimize noise, I send cover-letter and
> key patches #5 and 6 to every person involved. All other patches are sent
> individually to those pointed by scripts/get_maintainers.pl.
> 
> I'd like to move the series with my bitmap-for-next branch as a whole.


virtio-net changes are straight-forward, so

Acked-by: Michael S. Tsirkin <mst@redhat.com>


> v1: https://lore.kernel.org/netdev/20241228184949.31582-1-yury.norov@gmail.com/T/
> v2:
>  - rebase on top of today's origin/master;
>  - drop #v1-10: not needed since v6.14 @ Sagi Grinberg;
>  - #2, #3: fix picking next unused CPU @ Nick Child;
>  - fix typos, cleanup comments @ Bjorn Helgaas, Alexander Gordeev;
>  - CC Christoph Hellwig for the whole series.
> 
> Yury Norov (13):
>   objpool: rework objpool_pop()
>   virtio_net: simplify virtnet_set_affinity()
>   ibmvnic: simplify ibmvnic_set_queue_affinity()
>   powerpc/xmon: simplify xmon_batch_next_cpu()
>   cpumask: deprecate cpumask_next_wrap()
>   cpumask: re-introduce cpumask_next{,_and}_wrap()
>   cpumask: use cpumask_next_wrap() where appropriate
>   padata: switch padata_find_next() to using cpumask_next_wrap()
>   s390: switch stop_machine_yield() to using cpumask_next_wrap()
>   scsi: lpfc: switch lpfc_irq_rebalance() to using cpumask_next_wrap()
>   scsi: lpfc: rework lpfc_next_{online,present}_cpu()
>   PCI: hv: Switch hv_compose_multi_msi_req_get_cpu() to using
>     cpumask_next_wrap()
>   cpumask: drop cpumask_next_wrap_old()
> 
>  arch/powerpc/xmon/xmon.c            |  6 +--
>  arch/s390/kernel/processor.c        |  2 +-
>  drivers/net/ethernet/ibm/ibmvnic.c  | 18 +++++---
>  drivers/net/virtio_net.c            | 12 ++---
>  drivers/pci/controller/pci-hyperv.c |  3 +-
>  drivers/scsi/lpfc/lpfc.h            | 23 +++-------
>  drivers/scsi/lpfc/lpfc_init.c       |  2 +-
>  include/linux/cpumask.h             | 69 ++++++++++++++++++++---------
>  include/linux/objpool.h             |  7 ++-
>  kernel/padata.c                     |  2 +-
>  lib/cpumask.c                       | 37 +---------------
>  11 files changed, 81 insertions(+), 100 deletions(-)
> 
> -- 
> 2.43.0