Re: [PATCH 0/5] mm: Switch gfp_t to unsigned long

[Zi Yan]

On 19 Mar 2026, at 12:03, Brendan Jackman wrote:

> As pointed out by Vlastimil in [0], my proposal for __GFP_UNMAPPED is
> probably not needed for 32-bit. This offers a way out of the GFP flag
> scarcity so in preparation for this, flip gfp_t to be 64-bit on 64-bit
> machines, while leaving it 32-bit on 32-bit machines.
>
> For mm-internal code that prints raw GFP flags as hex, this just updates
> the format specifier to %lx. Presumably developers have a reason for
> wanting to see the whole flags word as a number in the log. For printks
> outside of mm/, I assume they are only using %x because the authors
> didn't know about %pGg, so they are converted to the latter as prep
> patches.

I think these %lx -> %pGg patches can be merged. They are nice cleanups.
Thank you for doing that.

Feel free to add Reviewed-by: Zi Yan <ziy@xxxxxxxxxx> to the first 4 patches.
(I did not put the tag in a newline, so that b4 will not mistakenly
take it for the whole series)

For patch 5, I will wait until you address the feedback from Vlastimil
and Matthew.

>
> Stuff I've done to try and find issues with this:
>
> - Built x86 allmodconfig and arm64 defconfig. Hopefully the 0-day bot
>   will alert me to the important builds I'm missing (I briefly tried to
>   build s390 and sparc64 but ran into tooling issues and gave up).
>
> - Ran some selftests on a x86 VM.
>
> - Poked around at stuff that refers to ___GFP_LAST_BIT to see if
>   anything looks wrong.
>
> - Ran this Coccinelle script to look for explicit casts to plain int:
>
> ---
> virtual report
>
> @r@
> gfp_t x;
> position p;
> @@
>
> (
>   (unsigned int)x@p
> |
>   (int)x@p
> )
>
> @script:python depends on report@
> p << r.p;
> @@
> msg = "WARNING: Explicit integer cast of gfp_t"
> coccilib.report.print_report(p[0], msg)
> ---
>
> Obviously this series doesn't "do anything" so maybe it doesn't make
> sense to merge it unless it goes in alongside __GFP_UNMAPPED, but it
> does seem to make sense to review it independently so I'm posting it as
> a separate series.
>
> [0] https://lore.kernel.org/all/6206d021-e6c2-4899-b426-cacd71ebd5ef@xxxxxxxxxx/
>
> To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> To: Michal Hocko <mhocko@xxxxxxxx>
> To: David Rientjes <rientjes@xxxxxxxxxx>
> To: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> To: Vlastimil Babka <vbabka@xxxxxxxxxx>
> To: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> To: Brendan Jackman <jackmanb@xxxxxxxxxx>
> To: Johannes Weiner <hannes@xxxxxxxxxxx>
> To: Zi Yan <ziy@xxxxxxxxxx>
> To: Harry Yoo <harry.yoo@xxxxxxxxxx>
> To: Hao Li <hao.li@xxxxxxxxx>
> To: Christoph Lameter <cl@xxxxxxxxxx>
> To: Roman Gushchin <roman.gushchin@xxxxxxxxx>
> To: Uladzislau Rezki <urezki@xxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
>
> Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
>
> ---
> Brendan Jackman (5):
>       drm/managed: Use special gfp_t format specifier
>       iwlegacy: 3945-mac: Use special gfp_t format specifier
>       mm/kfence: Use special gfp_t format specifier
>       net/rds: Use special gfp_t format specifier
>       mm: Change gfp_t to unsigned long
>
>  drivers/gpu/drm/drm_managed.c                  | 4 ++--
>  drivers/net/wireless/intel/iwlegacy/3945-mac.c | 4 ++--
>  include/linux/types.h                          | 2 +-
>  lib/test_lockup.c                              | 2 +-
>  mm/kfence/kfence_test.c                        | 2 +-
>  mm/oom_kill.c                                  | 2 +-
>  mm/page_alloc.c                                | 5 ++++-
>  mm/page_owner.c                                | 4 ++--
>  mm/slab_common.c                               | 2 +-
>  mm/slub.c                                      | 2 +-
>  mm/vmalloc.c                                   | 2 +-
>  net/rds/tcp_recv.c                             | 2 +-
>  12 files changed, 18 insertions(+), 15 deletions(-)
> ---
> base-commit: 8a30aeb0d1b4e4aaf7f7bae72f20f2ae75385ccb
> change-id: 20260319-gfp64-7a970a80ba4e
>
> Best regards,
> -- 
> Brendan Jackman <jackmanb@xxxxxxxxxx>


Best Regards,
Yan, Zi