[00/14] mmc: Replace kmap_atomic() with kmap_local_page()

Message

Adrian Hunter Oct. 5, 2022, 10:19 a.m. UTC

Hi

Here are patches primarily aimed at replacing kmap_atomic() with
kmap_local_page().

kmap_local_page() is equivalent to kmap_atomic() except that it does not
disable page faults or preemption. Where possible kmap_local_page() is
preferred to kmap_atomic() - refer kernel highmem documentation.

In these cases, there is no need to disable page faults or preemption, so
kmap_atomic() is replaced with kmap_local_page(), and, correspondingly,
kunmap_atomic() with kunmap_local().

That work raised the question of why local_irq_{save,restore}() was being
used with k[un]map_atomic().  It turns out to be for legacy reasons that
have gone away.

A long time ago the kmap_atomic API required a slot to be provided which
risked the possibility that other code might use the same slot at the
same time. Disabling interrupts prevented the possibility of an interrupt
handler doing that. However, that went away with
commit 3e4d3af501cc ("mm: stack based kmap_atomic()").

The work is mostly divided into separate patches, to enable separate review
for driver reviewers and to enable separate reverts if necessary.


Adrian Hunter (14):
      mmc: sdhci: Remove local_irq_{save,restore}() around k[un]map_atomic()
      mmc: sdhci: Remove local_irq_{save,restore}() around sg_miter_{next,stop}()
      mmc: sdhci: Replace kmap_atomic() with kmap_local_page()
      mmc: bcm2835: Remove local_irq_{save,restore}() around k[un]map_atomic()
      mmc: bcm2835: Remove local_irq_{save,restore}() around sg_miter_{next,stop}()
      mmc: bcm2835: Replace kmap_atomic() with kmap_local_page()
      mmc: mmc_test: Remove local_irq_{save,restore}() around sg_copy_{from,to}_buffer()
      mmc: tifm_sd: Remove local_irq_{save,restore}() around tifm_sd_transfer_data()
      mmc: tifm_sd: Remove local_irq_{save,restore}() around tifm_sd_bounce_block()
      mmc: tifm_sd: Replace kmap_atomic() with kmap_local_page()
      mmc: tmio_mmc_core: Remove local_irq_{save,restore}() around k[un]map_atomic()
      mmc: tmio_mmc_core: Replace kmap_atomic() with kmap_local_page()
      mmc: au1xmmc: Replace kmap_atomic() with kmap_local_page()
      mmc: wbsd: Replace kmap_atomic() with kmap_local_page()

 drivers/mmc/core/mmc_test.c              |  5 -----
 drivers/mmc/host/au1xmmc.c               |  8 ++++----
 drivers/mmc/host/bcm2835.c               | 12 ++----------
 drivers/mmc/host/renesas_sdhi_sys_dmac.c |  5 ++---
 drivers/mmc/host/sdhci.c                 | 30 ++++++++----------------------
 drivers/mmc/host/tifm_sd.c               | 28 ++++++++++------------------
 drivers/mmc/host/tmio_mmc.h              | 11 ++++-------
 drivers/mmc/host/tmio_mmc_core.c         | 10 ++++------
 drivers/mmc/host/wbsd.c                  | 10 +++++-----
 9 files changed, 39 insertions(+), 80 deletions(-)


Regards
Adrian

Comments

Ulf Hansson Oct. 24, 2022, 5:11 p.m. UTC | #1

On Wed, 5 Oct 2022 at 12:20, Adrian Hunter <[e-mail]> wrote:
>
> Hi
>
> Here are patches primarily aimed at replacing kmap_atomic() with
> kmap_local_page().
>
> kmap_local_page() is equivalent to kmap_atomic() except that it does not
> disable page faults or preemption. Where possible kmap_local_page() is
> preferred to kmap_atomic() - refer kernel highmem documentation.
>
> In these cases, there is no need to disable page faults or preemption, so
> kmap_atomic() is replaced with kmap_local_page(), and, correspondingly,
> kunmap_atomic() with kunmap_local().
>
> That work raised the question of why local_irq_{save,restore}() was being
> used with k[un]map_atomic().  It turns out to be for legacy reasons that
> have gone away.
>
> A long time ago the kmap_atomic API required a slot to be provided which
> risked the possibility that other code might use the same slot at the
> same time. Disabling interrupts prevented the possibility of an interrupt
> handler doing that. However, that went away with
> commit 3e4d3af501cc ("mm: stack based kmap_atomic()").
>
> The work is mostly divided into separate patches, to enable separate review
> for driver reviewers and to enable separate reverts if necessary.
>
>
> Adrian Hunter (14):
>       mmc: sdhci: Remove local_irq_{save,restore}() around k[un]map_atomic()
>       mmc: sdhci: Remove local_irq_{save,restore}() around sg_miter_{next,stop}()
>       mmc: sdhci: Replace kmap_atomic() with kmap_local_page()
>       mmc: bcm2835: Remove local_irq_{save,restore}() around k[un]map_atomic()
>       mmc: bcm2835: Remove local_irq_{save,restore}() around sg_miter_{next,stop}()
>       mmc: bcm2835: Replace kmap_atomic() with kmap_local_page()
>       mmc: mmc_test: Remove local_irq_{save,restore}() around sg_copy_{from,to}_buffer()
>       mmc: tifm_sd: Remove local_irq_{save,restore}() around tifm_sd_transfer_data()
>       mmc: tifm_sd: Remove local_irq_{save,restore}() around tifm_sd_bounce_block()
>       mmc: tifm_sd: Replace kmap_atomic() with kmap_local_page()
>       mmc: tmio_mmc_core: Remove local_irq_{save,restore}() around k[un]map_atomic()
>       mmc: tmio_mmc_core: Replace kmap_atomic() with kmap_local_page()
>       mmc: au1xmmc: Replace kmap_atomic() with kmap_local_page()
>       mmc: wbsd: Replace kmap_atomic() with kmap_local_page()
>
>  drivers/mmc/core/mmc_test.c              |  5 -----
>  drivers/mmc/host/au1xmmc.c               |  8 ++++----
>  drivers/mmc/host/bcm2835.c               | 12 ++----------
>  drivers/mmc/host/renesas_sdhi_sys_dmac.c |  5 ++---
>  drivers/mmc/host/sdhci.c                 | 30 ++++++++----------------------
>  drivers/mmc/host/tifm_sd.c               | 28 ++++++++++------------------
>  drivers/mmc/host/tmio_mmc.h              | 11 ++++-------
>  drivers/mmc/host/tmio_mmc_core.c         | 10 ++++------
>  drivers/mmc/host/wbsd.c                  | 10 +++++-----
>  9 files changed, 39 insertions(+), 80 deletions(-)
>
>
> Regards
> Adrian

Applied for next, thanks!

Kind regards
Uffe