Re: [PATCH v5 00/18] mm: Some cleanups for page allocator APIs

[Vlastimil Babka (SUSE)]

On 7/3/26 14:31, Brendan Jackman wrote:
> Based on mm-new.

Seems ready for mm-new to me. I suspect most further non-trivial page
allocator work will conflict, so better have it in mm to be based upon.

I was worried about Johannes' defrag fixes [1] that were supposed to be
stable bacported and thus would be better to add (the next revision) to
mm-new first. But seems like if I apply this series on mm-new, and then [1]
on top, nothing conflicts, so the ordering shouldn't matter.

[1] https://lore.kernel.org/all/20260626182215.1107966-1-hannes@xxxxxxxxxxx/

> This depends on moving alloc_tag to mm/:
> https://lore.kernel.org/all/aj5QBtJcphPElczI@lucifer/
> 
> Some tweaks and cleanups for page allocator entrypoint and flags. This
> is motivated by preparation for __GFP_UNMAPPED [1] (which will probably
> become ALLOC_UNMAPPED in its next iteration), but all this is supposed
> to be an improvement to the codebase in its own right: unifying code
> paths, reducing API surface, and removing GFP flags.
> 
> [1] https://lore.kernel.org/all/20260320-page_alloc-unmapped-v2-0-28bf1bd54f41@xxxxxxxxxx/
> 
> This started with unifying  __alloc_frozen_pages[_nolock]_noprof() and
> expanded from there.
> 
> Unifying the nolock allocator entrypoint with the normal allocator
> entrypoint means adding an alloc_flags argument to the later (only
> exposed within mm/). This presents an opportunity to take advantage of
> that arg to remove some GFP flags, if we add that alloc_flags arg a bit
> more broadly to allocator entrypoints.
> 
> To distinguish between mm-internal and "public" allocator entrypoints,
> it makes sense to use the __ prefix. There are already some public APIs
> with that prefix. For *alloc_pages*, just removing those variants seems
> like a nice cleanup anyway, so do that. For get_free_pages, the "__"
> variant is the _only_ variant and it's very widely used, so it doesn't
> seem worthwhile to modify that. Therefore, scope this "__" change
> specifically to the *alloc_pages* API, which means we leave the
> *folio_alloc* API untouched too, even though that could probably be
> cleaned up if so desired.
> 
> Tested:
> 
> - KVM, mm, and BPF selftests in a QEMU VM
> 
> - kunit.py on x86_64
> 
> - For the ALLOC_NO_CODETAG bits I just booted a VM and read
>   /proc/allocinfo. I confirmed that if I remove ALLOC_NO_CODETAG, the
>   kernel crashes in early boot, so I was at least booting code that
>   depends on this logic.
> 
> I used Google's internal version of Antigravity (AI coding harness) to
> do the repetitive bits, those commits are marked with Assisted-by, the
> rest is manual.
> 
> Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
> ---
> Changes in v5:
> - Just trivial non-functional fixes.
> - Link to v4: https://patch.msgid.link/20260702-alloc-trylock-v4-0-0af8ff387e80@xxxxxxxxxx
> 
> Changes in v4:
> - Fixed some (harmless) missing applications of ac->alloc_flags (local
>   Sashiko)
> - Fixed various build issues.
>    - Note that Sashiko pointed out a KMSAN build issue [0], I have
>      fixed it but KMSAN builds are currently broken by objtool [1]. At least
>      mm/kmsan/init.c compiles.
>      [2] https://lore.kernel.org/all/20260629141642.628271F00A3D@xxxxxxxxxxxxxxx/
>      [3] https://lore.kernel.org/all/20260630104434.GC751831@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/t/#u
> - Avoided setting ALLOC_NOFRAGMENT under ALLOC_NOLOCK (Sashiko, Harry)
> - Added patch to tweak alloc_flags_cma() interface (Vlastimil)
> - More commit messages fixups (various)
> - Added patch to create can_spin_trylock() (Harry)
> - Link to v3: https://patch.msgid.link/20260629-alloc-trylock-v3-0-57bef0eadbc2@xxxxxxxxxx
> 
> Changes in v3:
> - Created mm/page_alloc.h
> - Fixed EXPORT_SYMBOL() issues
> - Reworded commit messages per Sashiko's pointers
> - Dropped rename of alloc_flags arg in prepare_alloc_pages() (Suren)
> - Renamed gfp_to_alloc_flags_nonblocking() too after rebasing onto:
>   https://lore.kernel.org/all/20260623004600.113347-1-jp.kobryn@xxxxxxxxx/
> - Link to v2: https://patch.msgid.link/20260622-alloc-trylock-v2-0-31f31367d420@xxxxxxxxxx
> 
> Changes in v2:
> - Fixed up whitespace in nolock unification patch
> - Introduced ALLOC_DEFAULT to replace literal 0 for alloc_flags
> - All other patches are new
> - Link to v1: https://patch.msgid.link/20260617-alloc-trylock-v1-1-83fd7858832e@xxxxxxxxxx
> 
> ---
> Brendan Jackman (17):
>       mm/page_alloc: rename ALLOC_TRYLOCK -> ALLOC_NOLOCK
>       mm/page_alloc: some renames to clarify alloc_flags scopes
>       mm: name some args in a function declaration
>       mm: Split out internal page_alloc.h
>       mm/page_alloc: unify __alloc_frozen_pages[_nolock]_noprof()
>       mm/page_alloc: relax GFP WARN in nolock allocs
>       mm: move some stuff to mm/page_alloc.h
>       perf/x86/intel: Use higher-level allocator API
>       KVM: VMX: Use higher-level allocator API
>       x86/virt: Use higher-level allocator API
>       sgi-xp: Use higher-level allocator API
>       net/funeth: Switch to higher-level allocator API
>       mm: Remove __alloc_pages_node()
>       mm: Move __alloc_pages() to mm/page_alloc.h
>       mm: replace __GFP_NO_CODETAG with ALLOC_NO_CODETAG
>       mm/page_alloc: drop alloc_flags arg from alloc_flags_cma()
>       mm: factor out can_spin_trylock()
> 
> Vlastimil Babka (SUSE) (1):
>       mm: remove the __GFP_NO_OBJ_EXT flag
> 
>  Documentation/admin-guide/cgroup-v1/cpusets.rst  |   2 +-
>  Documentation/admin-guide/mm/transhuge.rst       |   2 +-
>  MAINTAINERS                                      |   1 +
>  arch/x86/events/intel/ds.c                       |   6 +-
>  arch/x86/kvm/vmx/vmx.c                           |   2 +-
>  arch/x86/virt/hw.c                               |   2 +-
>  drivers/misc/sgi-xp/xpc_uv.c                     |   5 +-
>  drivers/net/ethernet/fungible/funeth/funeth_rx.c |   2 +-
>  include/linux/alloc_tag.h                        |   4 +-
>  include/linux/gfp.h                              |  54 +---
>  include/linux/gfp_types.h                        |   7 -
>  include/linux/skbuff.h                           |   2 +-
>  include/trace/events/mmflags.h                   |  10 +-
>  mm/alloc_tag.c                                   |  23 +-
>  mm/compaction.c                                  |   5 +-
>  mm/hugetlb.c                                     |   4 +-
>  mm/internal.h                                    | 275 ++------------------
>  mm/khugepaged.c                                  |   1 +
>  mm/kmsan/init.c                                  |   2 +-
>  mm/memory-failure.c                              |   1 +
>  mm/memory_hotplug.c                              |   1 +
>  mm/mempolicy.c                                   |  11 +-
>  mm/migrate.c                                     |   1 +
>  mm/mm_init.c                                     |   1 +
>  mm/page_alloc.c                                  | 269 ++++++++++---------
>  mm/page_alloc.h                                  | 312 +++++++++++++++++++++++
>  mm/page_frag_cache.c                             |   6 +-
>  mm/page_isolation.c                              |   1 +
>  mm/page_owner.c                                  |   2 +-
>  mm/page_reporting.c                              |   1 +
>  mm/show_mem.c                                    |   1 +
>  mm/shuffle.c                                     |   1 +
>  mm/slub.c                                        |  17 +-
>  mm/swap.c                                        |   1 +
>  mm/vmscan.c                                      |   1 +
>  mm/vmstat.c                                      |   1 +
>  tools/include/linux/gfp_types.h                  |   7 -
>  37 files changed, 536 insertions(+), 508 deletions(-)
> ---
> base-commit: 32af3ff0925368eff29b2fed62f154150eb5dc10
> change-id: 20260617-alloc-trylock-14ad37dab337
> 
> Best regards,
> --  
> Brendan Jackman <jackmanb@xxxxxxxxxx>
>