From: Catalin Marinas <catalin.marinas@xxxxxxx>
Commit 4beba9486abd ("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@xxxxxxx>
Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
---
arch/arm64/Kconfig | 1 +
fs/proc/page.c | 2 +-
include/linux/page-flags.h | 2 +-
include/trace/events/mmflags.h | 8 ++++----
mm/Kconfig | 8 ++++++++
mm/huge_memory.c | 2 +-
6 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index f6737d2f37b2..f2435b62e0ba 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1948,6 +1948,7 @@ 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
diff --git a/fs/proc/page.c b/fs/proc/page.c
index a2873a617ae8..6f4b4bcb9b0d 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -218,7 +218,7 @@ 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
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 0b0ae5084e60..5dc7977edf9d 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -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
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index 11524cda4a95..4673e58a7626 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -90,10 +90,10 @@
#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
@@ -129,7 +129,7 @@ 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) \
diff --git a/mm/Kconfig b/mm/Kconfig
index ceec438c0741..a976cbb07bd6 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -999,6 +999,14 @@ 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
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1cc4a5f4791e..24974a4ce28f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -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) |
--
2.37.3.968.ga6b4b080e4-goog
