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Thadeu Lima de Souza Cascardo 6a204d4b14 mm/page_alloc: only set ALLOC_HIGHATOMIC for __GPF_HIGH allocations 
Commit 524c48072e ("mm/page_alloc: rename ALLOC_HIGH to
ALLOC_MIN_RESERVE") is the start of a series that explains how __GFP_HIGH,
which implies ALLOC_MIN_RESERVE, is going to be used instead of
__GFP_ATOMIC for high atomic reserves.

Commit eb2e2b425c ("mm/page_alloc: explicitly record high-order atomic
allocations in alloc_flags") introduced ALLOC_HIGHATOMIC for such
allocations of order higher than 0.  It still used __GFP_ATOMIC, though.

Then, commit 1ebbb21811 ("mm/page_alloc: explicitly define how
__GFP_HIGH non-blocking allocations accesses reserves") just turned that
check for !__GFP_DIRECT_RECLAIM, ignoring that high atomic reserves were
expected to test for __GFP_HIGH.

This leads to high atomic reserves being added for high-order GFP_NOWAIT
allocations and others that clear __GFP_DIRECT_RECLAIM, which is
unexpected.  Later, those reserves lead to 0-order allocations going to
the slow path and starting reclaim.

From /proc/pagetypeinfo, without the patch:

Node    0, zone      DMA, type   HighAtomic      0      0      0      0      0      0      0      0      0      0      0
Node    0, zone    DMA32, type   HighAtomic      1      8     10      9      7      3      0      0      0      0      0
Node    0, zone   Normal, type   HighAtomic     64     20     12      5      0      0      0      0      0      0      0

With the patch:

Node    0, zone      DMA, type   HighAtomic      0      0      0      0      0      0      0      0      0      0      0
Node    0, zone    DMA32, type   HighAtomic      0      0      0      0      0      0      0      0      0      0      0
Node    0, zone   Normal, type   HighAtomic      0      0      0      0      0      0      0      0      0      0      0

Link: https://lkml.kernel.org/r/20250814172245.1259625-1-cascardo@igalia.com
Fixes: 1ebbb21811 ("mm/page_alloc: explicitly define how __GFP_HIGH non-blocking allocations accesses reserves")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Tested-by: Helen Koike <koike@igalia.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-09-13 16:55:01 -07:00
arch riscv: use an atomic xchg in pudp_huge_get_and_clear() 2025-09-13 16:55:01 -07:00
block block: use largest_zero_folio in __blkdev_issue_zero_pages() 2025-09-13 16:54:54 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
Documentation docs/mm/damon/design: fix typo: s/sz_trtied/sz_tried/ 2025-09-13 16:54:49 -07:00
drivers mm: rename vm_ops->find_special_page() to vm_ops->find_normal_page() 2025-09-13 16:54:53 -07:00
fs mm: convert remaining users to mm_flags_*() accessors 2025-09-13 16:54:58 -07:00
include memcg: optimize exit to user space 2025-09-13 16:55:01 -07:00
init hardening: Require clang 20.1.0 for __counted_by 2025-08-29 12:04:53 -07:00
io_uring io_uring/kbuf: always use READ_ONCE() to read ring provided buffer lengths 2025-08-28 05:48:34 -06:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel mm: convert remaining users to mm_flags_*() accessors 2025-09-13 16:54:58 -07:00
lib lib/test_maple_tree.c: remove redundant semicolons 2025-09-13 16:55:01 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/page_alloc: only set ALLOC_HIGHATOMIC for __GPF_HIGH allocations 2025-09-13 16:55:01 -07:00
net net: ipv4: fix regression in local-broadcast routes 2025-08-28 10:52:30 +02:00
rust rust: allocator: add KUnit tests for alignment guarantees 2025-09-13 16:55:00 -07:00
samples Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
scripts kasan: fix GCC mem-intrinsic prefix with sw tags 2025-08-27 22:45:43 -07:00
security + Features 2025-08-04 08:17:28 -07:00
sound ALSA: hda/hdmi: Add pin fix for another HP EliteDesk 800 G4 model 2025-09-01 13:51:57 +02:00
tools selftests/damon: fix damon selftests by installing _common.sh 2025-09-13 16:54:59 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap .mailmap: add entry for Easwar Hariharan 2025-08-19 16:35:55 -07:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS gpio fixes for v6.17-rc4 2025-08-31 08:49:55 -07:00
Makefile Linux 6.17-rc4 2025-08-31 15:33:07 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.