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Subject: Re: [PATCH] hugetlb: allow to free gigantic pages regardless of the
 configuration
To:     akpm@linux-foundation.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H . Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Cc:     linux-riscv@lists.infradead.org, hch@infradead.org
References: <20190117183953.5990-1-aghiti@upmem.com>
From:   Alex Ghiti <alex@ghiti.fr>
Message-ID: <65c8ebc7-fc77-bd19-616d-e950ff6b080d@ghiti.fr>
Date:   Sun, 3 Feb 2019 13:17:56 -0500
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On 1/17/19 1:39 PM, Alexandre Ghiti wrote:
> 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
>   /*


Hi Andrew,

Can you consider this patch for inclusion in mm tree ? It lacks reviews 
from some
arch maintainers and has been reviewed by Mike Kravetz.
Tell me if I can do something to help,

Thanks,

Alex