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Subject[PATCH v5 4/4] hugetlb: allow to free gigantic pages regardless of the configuration
Date
On systems without CONTIG_ALLOC activated but that support gigantic pages,
boottime reserved gigantic pages can not be freed at all. This patch
simply enables the possibility to hand back those pages to memory
allocator.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
---
arch/arm64/Kconfig | 2 +-
arch/arm64/include/asm/hugetlb.h | 4 --
arch/powerpc/include/asm/book3s/64/hugetlb.h | 7 ---
arch/powerpc/platforms/Kconfig.cputype | 2 +-
arch/s390/Kconfig | 2 +-
arch/s390/include/asm/hugetlb.h | 3 --
arch/sh/Kconfig | 2 +-
arch/sparc/Kconfig | 2 +-
arch/x86/Kconfig | 2 +-
arch/x86/include/asm/hugetlb.h | 4 --
include/linux/gfp.h | 2 +-
mm/hugetlb.c | 54 ++++++++++++--------
mm/page_alloc.c | 4 +-
13 files changed, 42 insertions(+), 48 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 091a513b93e9..af687eff884a 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 CONTIG_ALLOC
+ select ARCH_HAS_GIGANTIC_PAGE
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..59893e766824 100644
--- a/arch/arm64/include/asm/hugetlb.h
+++ b/arch/arm64/include/asm/hugetlb.h
@@ -65,8 +65,4 @@ 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; }
-#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..d04a0bcc2f1c 100644
--- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
+++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
@@ -32,13 +32,6 @@ static inline int hstate_get_psize(struct hstate *hstate)
}
}

-#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
-static inline bool gigantic_page_supported(void)
-{
- return true;
-}
-#endif
-
/* hugepd entry valid bit */
#define HUGEPD_VAL_BITS (0x8000000000000000UL)

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index f677c8974212..dc0328de20cd 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 CONTIG_ALLOC
+ select ARCH_HAS_GIGANTIC_PAGE
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 1c57b83c76f5..d84e536796b1 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 CONTIG_ALLOC
+ select ARCH_HAS_GIGANTIC_PAGE
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..bd191560efcf 100644
--- a/arch/s390/include/asm/hugetlb.h
+++ b/arch/s390/include/asm/hugetlb.h
@@ -116,7 +116,4 @@ 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; }
-#endif
#endif /* _ASM_S390_HUGETLB_H */
diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index c7266302691c..404b12a0d871 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig
@@ -53,7 +53,7 @@ config SUPERH
select HAVE_FUTEX_CMPXCHG if FUTEX
select HAVE_NMI
select NEED_SG_DMA_LENGTH
- select ARCH_HAS_GIGANTIC_PAGE if CONTIG_ALLOC
+ select ARCH_HAS_GIGANTIC_PAGE

help
The SuperH is a RISC processor targeted for use in embedded systems
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index ca33c80870e2..234a6bd46e89 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -90,7 +90,7 @@ config SPARC64
select ARCH_CLOCKSOURCE_DATA
select ARCH_HAS_PTE_SPECIAL
select PCI_DOMAINS if PCI
- select ARCH_HAS_GIGANTIC_PAGE if CONTIG_ALLOC
+ select ARCH_HAS_GIGANTIC_PAGE

config ARCH_DEFCONFIG
string
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8ba90f3e0038..ff24eaeef211 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 CONTIG_ALLOC
+ select ARCH_HAS_GIGANTIC_PAGE
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..f65cfb48cfdd 100644
--- a/arch/x86/include/asm/hugetlb.h
+++ b/arch/x86/include/asm/hugetlb.h
@@ -17,8 +17,4 @@ 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; }
-#endif
-
#endif /* _ASM_X86_HUGETLB_H */
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 1f1ad9aeebb9..58ea44bf75de 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 afef61656c1e..7c57d58051ec 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1058,6 +1058,7 @@ static void free_gigantic_page(struct page *page, unsigned int order)
free_contig_range(page_to_pfn(page), 1 << order);
}

+#ifdef CONFIG_CONTIG_ALLOC
static int __alloc_gigantic_page(unsigned long start_pfn,
unsigned long nr_pages, gfp_t gfp_mask)
{
@@ -1142,11 +1143,20 @@ 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_CONTIG_ALLOC */
+static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
+ int nid, nodemask_t *nodemask)
+{
+ return NULL;
+}
+#endif /* CONFIG_CONTIG_ALLOC */

#else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
-static inline bool gigantic_page_supported(void) { return false; }
static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
- int nid, nodemask_t *nodemask) { return NULL; }
+ 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) { }
@@ -1156,9 +1166,6 @@ 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 +2283,24 @@ 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,
- nodemask_t *nodes_allowed)
+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;
+ /*
+ * Gigantic pages allocation depends on the capability for large page
+ * range allocation. If the system cannot provide alloc_contig_range,
+ * allow users to free gigantic pages.
+ */
+ if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
+ 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 +2340,7 @@ 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 +2369,10 @@ 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 +2424,6 @@ 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
@@ -2428,15 +2443,12 @@ 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 (nodes_allowed != &node_states[N_MEMORY])
NODEMASK_FREE(nodes_allowed);

- return len;
-out:
- NODEMASK_FREE(nodes_allowed);
- return err;
+ return err ? err : len;
}

static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ac9c45ffb344..a4547d90fa7a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8234,8 +8234,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
pfn_max_align_up(end), migratetype);
return ret;
}
+#endif /* CONFIG_CONTIG_ALLOC */

-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;

@@ -8247,7 +8248,6 @@ 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
/*
--
2.20.1
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