Re: [PATCH v5 14/22] powerpc/mm: Move pte_fragment_alloc() to a common location

From: Aneesh Kumar K.V
Date: Tue Sep 25 2018 - 22:43:50 EST

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In reply to: Christophe Leroy: "[PATCH v5 14/22] powerpc/mm: Move pte_fragment_alloc() to a common location"
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Christophe Leroy <christophe.leroy@xxxxxx> writes:

> In preparation of next patch which generalises the use of
> pte_fragment_alloc() for all, this patch moves the related functions
> in a place that is common to all subarches.
>
> The 8xx will need that for supporting 16k pages, as in that mode
> page tables still have a size of 4k.
>
> Since pte_fragment with only once fragment is not different
> from what is done in the general case, we can easily migrate all
> subarchs to pte fragments.
>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>

> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> ---
> arch/powerpc/include/asm/book3s/64/pgalloc.h | 1 +
> arch/powerpc/mm/Makefile | 4 +-
> arch/powerpc/mm/mmu_context_book3s64.c | 15 ----
> arch/powerpc/mm/pgtable-book3s64.c | 85 --------------------
> arch/powerpc/mm/pgtable-frag.c | 116 +++++++++++++++++++++++++++
> 5 files changed, 120 insertions(+), 101 deletions(-)
> create mode 100644 arch/powerpc/mm/pgtable-frag.c
>
> diff --git a/arch/powerpc/include/asm/book3s/64/pgalloc.h b/arch/powerpc/include/asm/book3s/64/pgalloc.h
> index bfed4cf3b2f3..6c2808c0f052 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgalloc.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgalloc.h
> @@ -39,6 +39,7 @@ extern struct vmemmap_backing *vmemmap_list;
> extern struct kmem_cache *pgtable_cache[];
> #define PGT_CACHE(shift) pgtable_cache[shift]
>
> +void pte_frag_destroy(void *pte_frag);
> extern pte_t *pte_fragment_alloc(struct mm_struct *, unsigned long, int);
> extern pmd_t *pmd_fragment_alloc(struct mm_struct *, unsigned long);
> extern void pte_fragment_free(unsigned long *, int);
> diff --git a/arch/powerpc/mm/Makefile b/arch/powerpc/mm/Makefile
> index d0c1ce1297e3..db2f001183d1 100644
> --- a/arch/powerpc/mm/Makefile
> +++ b/arch/powerpc/mm/Makefile
> @@ -15,7 +15,9 @@ obj-$(CONFIG_PPC_MMU_NOHASH) += mmu_context_nohash.o tlb_nohash.o \
> obj-$(CONFIG_PPC_BOOK3E) += tlb_low_$(BITS)e.o
> hash64-$(CONFIG_PPC_NATIVE) := hash_native_64.o
> obj-$(CONFIG_PPC_BOOK3E_64) += pgtable-book3e.o
> -obj-$(CONFIG_PPC_BOOK3S_64) += pgtable-hash64.o hash_utils_64.o slb.o $(hash64-y) mmu_context_book3s64.o pgtable-book3s64.o
> +obj-$(CONFIG_PPC_BOOK3S_64) += pgtable-hash64.o hash_utils_64.o slb.o \
> + $(hash64-y) mmu_context_book3s64.o \
> + pgtable-book3s64.o pgtable-frag.o
> obj-$(CONFIG_PPC_RADIX_MMU) += pgtable-radix.o tlb-radix.o
> obj-$(CONFIG_PPC_STD_MMU_32) += ppc_mmu_32.o hash_low_32.o mmu_context_hash32.o
> obj-$(CONFIG_PPC_STD_MMU) += tlb_hash$(BITS).o
> diff --git a/arch/powerpc/mm/mmu_context_book3s64.c b/arch/powerpc/mm/mmu_context_book3s64.c
> index 510f103d7813..f720c5cc0b5e 100644
> --- a/arch/powerpc/mm/mmu_context_book3s64.c
> +++ b/arch/powerpc/mm/mmu_context_book3s64.c
> @@ -164,21 +164,6 @@ static void destroy_contexts(mm_context_t *ctx)
> }
> }
>
> -static void pte_frag_destroy(void *pte_frag)
> -{
> - int count;
> - struct page *page;
> -
> - page = virt_to_page(pte_frag);
> - /* drop all the pending references */
> - count = ((unsigned long)pte_frag & ~PAGE_MASK) >> PTE_FRAG_SIZE_SHIFT;
> - /* We allow PTE_FRAG_NR fragments from a PTE page */
> - if (atomic_sub_and_test(PTE_FRAG_NR - count, &page->pt_frag_refcount)) {
> - pgtable_page_dtor(page);
> - __free_page(page);
> - }
> -}
> -
> static void pmd_frag_destroy(void *pmd_frag)
> {
> int count;
> diff --git a/arch/powerpc/mm/pgtable-book3s64.c b/arch/powerpc/mm/pgtable-book3s64.c
> index 01d7c0f7c4f0..723cd324fa34 100644
> --- a/arch/powerpc/mm/pgtable-book3s64.c
> +++ b/arch/powerpc/mm/pgtable-book3s64.c
> @@ -317,91 +317,6 @@ void pmd_fragment_free(unsigned long *pmd)
> }
> }
>
> -static pte_t *get_pte_from_cache(struct mm_struct *mm)
> -{
> - void *pte_frag, *ret;
> -
> - spin_lock(&mm->page_table_lock);
> - ret = mm->context.pte_frag;
> - if (ret) {
> - pte_frag = ret + PTE_FRAG_SIZE;
> - /*
> - * If we have taken up all the fragments mark PTE page NULL
> - */
> - if (((unsigned long)pte_frag & ~PAGE_MASK) == 0)
> - pte_frag = NULL;
> - mm->context.pte_frag = pte_frag;
> - }
> - spin_unlock(&mm->page_table_lock);
> - return (pte_t *)ret;
> -}
> -
> -static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel)
> -{
> - void *ret = NULL;
> - struct page *page;
> -
> - if (!kernel) {
> - page = alloc_page(PGALLOC_GFP | __GFP_ACCOUNT);
> - if (!page)
> - return NULL;
> - if (!pgtable_page_ctor(page)) {
> - __free_page(page);
> - return NULL;
> - }
> - } else {
> - page = alloc_page(PGALLOC_GFP);
> - if (!page)
> - return NULL;
> - }
> -
> - atomic_set(&page->pt_frag_refcount, 1);
> -
> - ret = page_address(page);
> - /*
> - * if we support only one fragment just return the
> - * allocated page.
> - */
> - if (PTE_FRAG_NR == 1)
> - return ret;
> - spin_lock(&mm->page_table_lock);
> - /*
> - * If we find pgtable_page set, we return
> - * the allocated page with single fragement
> - * count.
> - */
> - if (likely(!mm->context.pte_frag)) {
> - atomic_set(&page->pt_frag_refcount, PTE_FRAG_NR);
> - mm->context.pte_frag = ret + PTE_FRAG_SIZE;
> - }
> - spin_unlock(&mm->page_table_lock);
> -
> - return (pte_t *)ret;
> -}
> -
> -pte_t *pte_fragment_alloc(struct mm_struct *mm, unsigned long vmaddr, int kernel)
> -{
> - pte_t *pte;
> -
> - pte = get_pte_from_cache(mm);
> - if (pte)
> - return pte;
> -
> - return __alloc_for_ptecache(mm, kernel);
> -}
> -
> -void pte_fragment_free(unsigned long *table, int kernel)
> -{
> - struct page *page = virt_to_page(table);
> -
> - BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0);
> - if (atomic_dec_and_test(&page->pt_frag_refcount)) {
> - if (!kernel)
> - pgtable_page_dtor(page);
> - __free_page(page);
> - }
> -}
> -
> static inline void pgtable_free(void *table, int index)
> {
> switch (index) {
> diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
> new file mode 100644
> index 000000000000..d61e7c2a9a79
> --- /dev/null
> +++ b/arch/powerpc/mm/pgtable-frag.c
> @@ -0,0 +1,116 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Handling Page Tables through page fragments
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/gfp.h>
> +#include <linux/mm.h>
> +#include <linux/percpu.h>
> +#include <linux/hardirq.h>
> +#include <linux/hugetlb.h>
> +#include <asm/pgalloc.h>
> +#include <asm/tlbflush.h>
> +#include <asm/tlb.h>
> +
> +void pte_frag_destroy(void *pte_frag)
> +{
> + int count;
> + struct page *page;
> +
> + page = virt_to_page(pte_frag);
> + /* drop all the pending references */
> + count = ((unsigned long)pte_frag & ~PAGE_MASK) >> PTE_FRAG_SIZE_SHIFT;
> + /* We allow PTE_FRAG_NR fragments from a PTE page */
> + if (atomic_sub_and_test(PTE_FRAG_NR - count, &page->pt_frag_refcount)) {
> + pgtable_page_dtor(page);
> + __free_page(page);
> + }
> +}
> +
> +static pte_t *get_pte_from_cache(struct mm_struct *mm)
> +{
> + void *pte_frag, *ret;
> +
> + spin_lock(&mm->page_table_lock);
> + ret = mm->context.pte_frag;
> + if (ret) {
> + pte_frag = ret + PTE_FRAG_SIZE;
> + /*
> + * If we have taken up all the fragments mark PTE page NULL
> + */
> + if (((unsigned long)pte_frag & ~PAGE_MASK) == 0)
> + pte_frag = NULL;
> + mm->context.pte_frag = pte_frag;
> + }
> + spin_unlock(&mm->page_table_lock);
> + return (pte_t *)ret;
> +}
> +
> +static pte_t *__alloc_for_ptecache(struct mm_struct *mm, int kernel)
> +{
> + void *ret = NULL;
> + struct page *page;
> +
> + if (!kernel) {
> + page = alloc_page(PGALLOC_GFP | __GFP_ACCOUNT);
> + if (!page)
> + return NULL;
> + if (!pgtable_page_ctor(page)) {
> + __free_page(page);
> + return NULL;
> + }
> + } else {
> + page = alloc_page(PGALLOC_GFP);
> + if (!page)
> + return NULL;
> + }
> +
> + atomic_set(&page->pt_frag_refcount, 1);
> +
> + ret = page_address(page);
> + /*
> + * if we support only one fragment just return the
> + * allocated page.
> + */
> + if (PTE_FRAG_NR == 1)
> + return ret;
> + spin_lock(&mm->page_table_lock);
> + /*
> + * If we find pgtable_page set, we return
> + * the allocated page with single fragement
> + * count.
> + */
> + if (likely(!mm->context.pte_frag)) {
> + atomic_set(&page->pt_frag_refcount, PTE_FRAG_NR);
> + mm->context.pte_frag = ret + PTE_FRAG_SIZE;
> + }
> + spin_unlock(&mm->page_table_lock);
> +
> + return (pte_t *)ret;
> +}
> +
> +pte_t *pte_fragment_alloc(struct mm_struct *mm, unsigned long vmaddr, int kernel)
> +{
> + pte_t *pte;
> +
> + pte = get_pte_from_cache(mm);
> + if (pte)
> + return pte;
> +
> + return __alloc_for_ptecache(mm, kernel);
> +}
> +
> +void pte_fragment_free(unsigned long *table, int kernel)
> +{
> + struct page *page = virt_to_page(table);
> +
> + BUG_ON(atomic_read(&page->pt_frag_refcount) <= 0);
> + if (atomic_dec_and_test(&page->pt_frag_refcount)) {
> + if (!kernel)
> + pgtable_page_dtor(page);
> + __free_page(page);
> + }
> +}
> --
> 2.13.3

Next message: Aneesh Kumar K.V: "Re: [PATCH v5 15/22] powerpc/mm: Avoid useless lock with single page fragments"
Previous message: Zong Li: "Re: [PATCH 3/5] lib: Add umoddi3 and udivmoddi4 of GCC library routines"
In reply to: Christophe Leroy: "[PATCH v5 14/22] powerpc/mm: Move pte_fragment_alloc() to a common location"
Next in thread: Christophe Leroy: "[PATCH v5 09/22] powerpc/8xx: don't use r12/SPRN_SPRG_SCRATCH2 in TLB Miss handlers"
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