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mm: Do not enable PG_arch_2 for all 64-bit architectures 

Commit 4beba9486a ("mm: Add PG_arch_2 page flag") introduced a new
page flag for all 64-bit architectures. However, even if an architecture
is 64-bit, it may still have limited spare bits in the 'flags' member of
'struct page'. This may happen if an architecture enables SPARSEMEM
without SPARSEMEM_VMEMMAP as is the case with the newly added loongarch.
This architecture port needs 19 more bits for the sparsemem section
information and, while it is currently fine with PG_arch_2, adding any
more PG_arch_* flags will trigger build-time warnings.

Add a new CONFIG_ARCH_USES_PG_ARCH_X option which can be selected by
architectures that need more PG_arch_* flags beyond PG_arch_1. Select it
on arm64.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[pcc@google.com: fix build with CONFIG_ARM64_MTE disabled]
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Steven Price <steven.price@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221104011041.290951-2-pcc@google.com
This commit is contained in:
Catalin Marinas 2022-11-03 18:10:34 -07:00 committed by Marc Zyngier
parent 30a0b95b13
commit b0284cd29a
6 changed files with 16 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm64/Kconfig
View File

@ -1965,6 +1965,7 @@ config ARM64_MTE
depends on ARM64_PAN
select ARCH_HAS_SUBPAGE_FAULTS
select ARCH_USES_HIGH_VMA_FLAGS
select ARCH_USES_PG_ARCH_X
help
Memory Tagging (part of the ARMv8.5 Extensions) provides
architectural support for run-time, always-on detection of

2
fs/proc/page.c
View File

@ -219,7 +219,7 @@ u64 stable_page_flags(struct page *page)
u |= kpf_copy_bit(k, KPF_PRIVATE_2, PG_private_2);
u |= kpf_copy_bit(k, KPF_OWNER_PRIVATE, PG_owner_priv_1);
u |= kpf_copy_bit(k, KPF_ARCH, PG_arch_1);
#ifdef CONFIG_64BIT
#ifdef CONFIG_ARCH_USES_PG_ARCH_X
u |= kpf_copy_bit(k, KPF_ARCH_2, PG_arch_2);
#endif

2
include/linux/page-flags.h
View File

@ -132,7 +132,7 @@ enum pageflags {
PG_young,
PG_idle,
#endif
#ifdef CONFIG_64BIT
#ifdef CONFIG_ARCH_USES_PG_ARCH_X
PG_arch_2,
#endif
#ifdef CONFIG_KASAN_HW_TAGS

8
include/trace/events/mmflags.h
View File

@ -91,10 +91,10 @@
#define IF_HAVE_PG_IDLE(flag,string)
#endif
#ifdef CONFIG_64BIT
#define IF_HAVE_PG_ARCH_2(flag,string) ,{1UL << flag, string}
#ifdef CONFIG_ARCH_USES_PG_ARCH_X
#define IF_HAVE_PG_ARCH_X(flag,string) ,{1UL << flag, string}
#else
#define IF_HAVE_PG_ARCH_2(flag,string)
#define IF_HAVE_PG_ARCH_X(flag,string)
#endif
#ifdef CONFIG_KASAN_HW_TAGS
@ -130,7 +130,7 @@ IF_HAVE_PG_UNCACHED(PG_uncached, "uncached" ) \
IF_HAVE_PG_HWPOISON(PG_hwpoison, "hwpoison" ) \
IF_HAVE_PG_IDLE(PG_young, "young" ) \
IF_HAVE_PG_IDLE(PG_idle, "idle" ) \
IF_HAVE_PG_ARCH_2(PG_arch_2, "arch_2" ) \
IF_HAVE_PG_ARCH_X(PG_arch_2, "arch_2" ) \
IF_HAVE_PG_SKIP_KASAN_POISON(PG_skip_kasan_poison, "skip_kasan_poison")
#define show_page_flags(flags) \

8
mm/Kconfig
View File

@ -1005,6 +1005,14 @@ config ARCH_USES_HIGH_VMA_FLAGS
config ARCH_HAS_PKEYS
bool
config ARCH_USES_PG_ARCH_X
bool
help
Enable the definition of PG_arch_x page flags with x > 1. Only
suitable for 64-bit architectures with CONFIG_FLATMEM or
CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
enough room for additional bits in page->flags.
config VM_EVENT_COUNTERS
default y
bool "Enable VM event counters for /proc/vmstat" if EXPERT

2
mm/huge_memory.c
View File

@ -2444,7 +2444,7 @@ static void __split_huge_page_tail(struct page *head, int tail,
(1L << PG_workingset) |
(1L << PG_locked) |
(1L << PG_unevictable) |
#ifdef CONFIG_64BIT
#ifdef CONFIG_ARCH_USES_PG_ARCH_X
(1L << PG_arch_2) |
#endif
(1L << PG_dirty) |