mm: Some cleanups for page allocator APIs

This is based on mm-new, it depends on moving alloc_tag to mm/ [0].

[0] 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-...

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@google.com>
---
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.ko...
- Link to v2: https://patch.msgid.link/20260622-alloc-trylock-v2-0-31f3...

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-v1-1-83fd...

---
Brendan Jackman (16):
      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: 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                     |   2 +-
 drivers/net/ethernet/fungible/funeth/funeth_rx.c |   2 +-
 include/linux/gfp.h                              |  54 +---
 mm/alloc_tag.c                                   |  22 +-
 mm/compaction.c                                  |   5 +-
 mm/hugetlb.c                                     |   4 +-
 mm/internal.h                                    | 253 ------------------
 mm/khugepaged.c                                  |   1 +
 mm/memory-failure.c                              |   1 +
 mm/memory_hotplug.c                              |   1 +
 mm/mempolicy.c                                   |  11 +-
 mm/mm_init.c                                     |   1 +
 mm/page_alloc.c                                  | 259 ++++++++++---------
 mm/page_alloc.h                                  | 316 +++++++++++++++++++++++
 mm/page_frag_cache.c                             |   6 +-
 mm/page_isolation.c                              |   1 +
 mm/page_owner.c                                  |   2 +-
 mm/show_mem.c                                    |   1 +
 mm/slub.c                                        |   7 +-
 mm/swap.c                                        |   1 +
 mm/vmscan.c                                      |   1 +
 mm/vmstat.c                                      |   1 +
 tools/include/linux/gfp_types.h                  |   7 -
 29 files changed, 506 insertions(+), 468 deletions(-)
---
base-commit: ec005628e9dbcef26b761fa860f264fe6e5fd690
change-id: 20260617-alloc-trylock-14ad37dab337

Best regards,
--  
Brendan Jackman <jackmanb@google.com>