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Subject[PATCH] hugetlb: allow to free gigantic pages regardless of the configuration
Date
From: Alexandre Ghiti <alex@ghiti.fr>

On systems without CMA or (MEMORY_ISOLATION && COMPACTION) activated but
that support gigantic pages, boottime reserved gigantic pages can not be
freed at all. This patchs simply enables the possibility to hand back
those pages to memory allocator.

This commit then renames gigantic_page_supported and
ARCH_HAS_GIGANTIC_PAGE to make them more accurate. Indeed, those values
being false does not mean that the system cannot use gigantic pages: it
just means that runtime allocation of gigantic pages is not supported,
one can still allocate boottime gigantic pages if the architecture supports
it.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
---

- Compiled on all architectures
- Tested on riscv architecture

arch/arm64/Kconfig | 2 +-
arch/arm64/include/asm/hugetlb.h | 7 +++--
arch/powerpc/include/asm/book3s/64/hugetlb.h | 4 +--
arch/powerpc/platforms/Kconfig.cputype | 2 +-
arch/s390/Kconfig | 2 +-
arch/s390/include/asm/hugetlb.h | 7 +++--
arch/x86/Kconfig | 2 +-
arch/x86/include/asm/hugetlb.h | 7 +++--
fs/Kconfig | 2 +-
include/linux/gfp.h | 2 +-
mm/hugetlb.c | 43 +++++++++++++++-------------
mm/page_alloc.c | 4 +--
12 files changed, 48 insertions(+), 36 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a4168d366127..18239cbd7fcd 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -18,7 +18,7 @@ config ARM64
select ARCH_HAS_FAST_MULTIPLIER
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
- select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
+ select ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION if (MEMORY_ISOLATION && COMPACTION) || CMA
select ARCH_HAS_KCOV
select ARCH_HAS_MEMBARRIER_SYNC_CORE
select ARCH_HAS_PTE_SPECIAL
diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
index fb6609875455..797fc77eabcd 100644
--- a/arch/arm64/include/asm/hugetlb.h
+++ b/arch/arm64/include/asm/hugetlb.h
@@ -65,8 +65,11 @@ extern void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,

#include <asm-generic/hugetlb.h>

-#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-static inline bool gigantic_page_supported(void) { return true; }
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION
+static inline bool gigantic_page_runtime_allocation_supported(void)
+{
+ return true;
+}
#endif

#endif /* __ASM_HUGETLB_H */
diff --git a/arch/powerpc/include/asm/book3s/64/hugetlb.h b/arch/powerpc/include/asm/book3s/64/hugetlb.h
index 5b0177733994..7711f0e2c7e5 100644
--- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
+++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
@@ -32,8 +32,8 @@ static inline int hstate_get_psize(struct hstate *hstate)
}
}

-#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-static inline bool gigantic_page_supported(void)
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION
+static inline bool gigantic_page_runtime_allocation_supported(void)
{
return true;
}
diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 8c7464c3f27f..779e06bac697 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -319,7 +319,7 @@ config ARCH_ENABLE_SPLIT_PMD_PTLOCK
config PPC_RADIX_MMU
bool "Radix MMU Support"
depends on PPC_BOOK3S_64
- select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
+ select ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION if (MEMORY_ISOLATION && COMPACTION) || CMA
default y
help
Enable support for the Power ISA 3.0 Radix style MMU. Currently this
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index ed554b09eb3f..6776eef6a9ae 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -69,7 +69,7 @@ config S390
select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
- select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
+ select ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION if (MEMORY_ISOLATION && COMPACTION) || CMA
select ARCH_HAS_KCOV
select ARCH_HAS_PTE_SPECIAL
select ARCH_HAS_SET_MEMORY
diff --git a/arch/s390/include/asm/hugetlb.h b/arch/s390/include/asm/hugetlb.h
index 2d1afa58a4b6..57c952f5388e 100644
--- a/arch/s390/include/asm/hugetlb.h
+++ b/arch/s390/include/asm/hugetlb.h
@@ -116,7 +116,10 @@ static inline pte_t huge_pte_modify(pte_t pte, pgprot_t newprot)
return pte_modify(pte, newprot);
}

-#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-static inline bool gigantic_page_supported(void) { return true; }
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION
+static inline bool gigantic_page_runtime_allocation_supported(void)
+{
+ return true;
+}
#endif
#endif /* _ASM_S390_HUGETLB_H */
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6185d4f33296..a88f5a4311c9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -23,7 +23,7 @@ config X86_64
def_bool y
depends on 64BIT
# Options that are inherently 64-bit kernel only:
- select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
+ select ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION if (MEMORY_ISOLATION && COMPACTION) || CMA
select ARCH_SUPPORTS_INT128
select ARCH_USE_CMPXCHG_LOCKREF
select HAVE_ARCH_SOFT_DIRTY
diff --git a/arch/x86/include/asm/hugetlb.h b/arch/x86/include/asm/hugetlb.h
index 7469d321f072..5a5e7119ced4 100644
--- a/arch/x86/include/asm/hugetlb.h
+++ b/arch/x86/include/asm/hugetlb.h
@@ -17,8 +17,11 @@ static inline void arch_clear_hugepage_flags(struct page *page)
{
}

-#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-static inline bool gigantic_page_supported(void) { return true; }
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION
+static inline bool gigantic_page_runtime_allocation_supported(void)
+{
+ return true;
+}
#endif

#endif /* _ASM_X86_HUGETLB_H */
diff --git a/fs/Kconfig b/fs/Kconfig
index ac474a61be37..4192d1fde0f0 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -207,7 +207,7 @@ config HUGETLB_PAGE
config MEMFD_CREATE
def_bool TMPFS || HUGETLBFS

-config ARCH_HAS_GIGANTIC_PAGE
+config ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION
bool

source "fs/configfs/Kconfig"
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 5f5e25fd6149..79ff86fabd42 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -589,8 +589,8 @@ static inline bool pm_suspended_storage(void)
/* The below functions must be run on a range from a single zone. */
extern int alloc_contig_range(unsigned long start, unsigned long end,
unsigned migratetype, gfp_t gfp_mask);
-extern void free_contig_range(unsigned long pfn, unsigned nr_pages);
#endif
+extern void free_contig_range(unsigned long pfn, unsigned int nr_pages);

#ifdef CONFIG_CMA
/* CMA stuff */
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 745088810965..9893ba26b3b8 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1035,7 +1035,6 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
((node = hstate_next_node_to_free(hs, mask)) || 1); \
nr_nodes--)

-#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
static void destroy_compound_gigantic_page(struct page *page,
unsigned int order)
{
@@ -1058,6 +1057,7 @@ static void free_gigantic_page(struct page *page, unsigned int order)
free_contig_range(page_to_pfn(page), 1 << order);
}

+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION
static int __alloc_gigantic_page(unsigned long start_pfn,
unsigned long nr_pages, gfp_t gfp_mask)
{
@@ -1143,22 +1143,19 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
static void prep_compound_gigantic_page(struct page *page, unsigned int order);

-#else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
-static inline bool gigantic_page_supported(void) { return false; }
+#else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE_RUNTIME_ALLOCATION */
+static inline bool gigantic_page_runtime_allocation_supported(void)
+{
+ return false;
+}
static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
int nid, nodemask_t *nodemask) { return NULL; }
-static inline void free_gigantic_page(struct page *page, unsigned int order) { }
-static inline void destroy_compound_gigantic_page(struct page *page,
- unsigned int order) { }
#endif

static void update_and_free_page(struct hstate *h, struct page *page)
{
int i;

- if (hstate_is_gigantic(h) && !gigantic_page_supported())
- return;
-
h->nr_huge_pages--;
h->nr_huge_pages_node[page_to_nid(page)]--;
for (i = 0; i < pages_per_huge_page(h); i++) {
@@ -2276,13 +2273,20 @@ static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
}

#define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
-static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
+static int set_max_huge_pages(struct hstate *h, unsigned long count,
nodemask_t *nodes_allowed)
{
unsigned long min_count, ret;

- if (hstate_is_gigantic(h) && !gigantic_page_supported())
- return h->max_huge_pages;
+ if (hstate_is_gigantic(h) &&
+ !gigantic_page_runtime_allocation_supported()) {
+ spin_lock(&hugetlb_lock);
+ if (count > persistent_huge_pages(h)) {
+ spin_unlock(&hugetlb_lock);
+ return -EINVAL;
+ }
+ goto decrease_pool;
+ }

/*
* Increase the pool size
@@ -2322,6 +2326,7 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
goto out;
}

+decrease_pool:
/*
* Decrease the pool size
* First return free pages to the buddy allocator (being careful
@@ -2350,9 +2355,10 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
break;
}
out:
- ret = persistent_huge_pages(h);
+ h->max_huge_pages = persistent_huge_pages(h);
spin_unlock(&hugetlb_lock);
- return ret;
+
+ return 0;
}

#define HSTATE_ATTR_RO(_name) \
@@ -2404,11 +2410,6 @@ static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
int err;
NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);

- if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
- err = -EINVAL;
- goto out;
- }
-
if (nid == NUMA_NO_NODE) {
/*
* global hstate attribute
@@ -2428,7 +2429,9 @@ static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
} else
nodes_allowed = &node_states[N_MEMORY];

- h->max_huge_pages = set_max_huge_pages(h, count, nodes_allowed);
+ err = set_max_huge_pages(h, count, nodes_allowed);
+ if (err)
+ goto out;

if (nodes_allowed != &node_states[N_MEMORY])
NODEMASK_FREE(nodes_allowed);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cde5dac6229a..81b931db85a1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8241,8 +8241,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
pfn_max_align_up(end), migratetype);
return ret;
}
+#endif

-void free_contig_range(unsigned long pfn, unsigned nr_pages)
+void free_contig_range(unsigned long pfn, unsigned int nr_pages)
{
unsigned int count = 0;

@@ -8254,7 +8255,6 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
}
WARN(count != 0, "%d pages are still in use!\n", count);
}
-#endif

#ifdef CONFIG_MEMORY_HOTPLUG
/*
--
2.16.2
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