Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752734AbaJ1Klm (ORCPT ); Tue, 28 Oct 2014 06:41:42 -0400 Received: from mail-wg0-f43.google.com ([74.125.82.43]:37388 "EHLO mail-wg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751406AbaJ1Kli (ORCPT ); Tue, 28 Oct 2014 06:41:38 -0400 Date: Tue, 28 Oct 2014 10:41:31 +0000 From: Steve Capper To: "Aneesh Kumar K.V" Cc: akpm@linux-foundation.org, Andrea Arcangeli , benh@kernel.crashing.org, mpe@ellerman.id.au, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org Subject: Re: [PATCH V3 1/2] mm: Update generic gup implementation to handle hugepage directory Message-ID: <20141028104129.GA4187@linaro.org> References: <1414233860-7683-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1414233860-7683-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Oct 25, 2014 at 04:14:19PM +0530, Aneesh Kumar K.V wrote: > Update generic gup implementation with powerpc specific details. > On powerpc at pmd level we can have hugepte, normal pmd pointer > or a pointer to the hugepage directory. > > Signed-off-by: Aneesh Kumar K.V > --- Hi, Apologies for not getting to this yesterday. I have some comments below: > Changes from V3: > * Explain pgd_huge, also move the definition to linux/hugetlb.h. > Both pgd_huge and is_hugepd are related to hugepages and hugetlb.h > is the right header > > arch/arm/include/asm/pgtable.h | 2 + > arch/arm64/include/asm/pgtable.h | 2 + > arch/powerpc/include/asm/page.h | 1 + > include/linux/hugetlb.h | 30 +++++++++++ > include/linux/mm.h | 7 +++ > mm/gup.c | 113 +++++++++++++++++++-------------------- > 6 files changed, 96 insertions(+), 59 deletions(-) > > diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h > index 3b30062..c52d261 100644 > --- a/arch/arm/include/asm/pgtable.h > +++ b/arch/arm/include/asm/pgtable.h > @@ -181,6 +181,8 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD]; > /* to find an entry in a kernel page-table-directory */ > #define pgd_offset_k(addr) pgd_offset(&init_mm, addr) > > +#define pgd_huge(pgd) (0) > + Please remove this from the patch as it is no longer needed due to some changes below. > #define pmd_none(pmd) (!pmd_val(pmd)) > #define pmd_present(pmd) (pmd_val(pmd)) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 41a43bf..f532a14 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -464,6 +464,8 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot) > extern pgd_t swapper_pg_dir[PTRS_PER_PGD]; > extern pgd_t idmap_pg_dir[PTRS_PER_PGD]; > > +#define pgd_huge(pgd) (0) > + This too can be removed (see below)... > /* > * Encode and decode a swap entry: > * bits 0-1: present (must be zero) > diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h > index 26fe1ae..f973fce 100644 > --- a/arch/powerpc/include/asm/page.h > +++ b/arch/powerpc/include/asm/page.h > @@ -380,6 +380,7 @@ static inline int hugepd_ok(hugepd_t hpd) > #endif > > #define is_hugepd(pdep) (hugepd_ok(*((hugepd_t *)(pdep)))) > +#define pgd_huge pgd_huge > int pgd_huge(pgd_t pgd); > #else /* CONFIG_HUGETLB_PAGE */ > #define is_hugepd(pdep) 0 > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 6e6d338..de63dbc 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -175,6 +175,36 @@ static inline void __unmap_hugepage_range(struct mmu_gather *tlb, > } > > #endif /* !CONFIG_HUGETLB_PAGE */ > +/* > + * hugepages at page global directory. If arch support > + * hugepages at pgd level, they need to define this. > + */ > +#ifndef pgd_huge > +#define pgd_huge(x) 0 > +#endif This sequence now means we no longer need per-arch non-trivial definitions of pgd_huge. i.e. it makes the arch/arm and arch/arm64 changes above superfluous. > + > +#ifndef is_hugepd > +/* > + * Some architectures requires a hugepage directory format that is > + * required to support multiple hugepage sizes. For example > + * a4fe3ce7699bfe1bd88f816b55d42d8fe1dac655 introduced the same > + * on powerpc. This allows for a more flexible hugepage pagetable > + * layout. > + */ > +typedef struct { unsigned long pd; } hugepd_t; > +#define is_hugepd(hugepd) (0) > +#define __hugepd(x) ((hugepd_t) { (x) }) > +static inline int gup_huge_pd(hugepd_t hugepd, unsigned long addr, > + unsigned pdshift, unsigned long end, > + int write, struct page **pages, int *nr) > +{ > + return 0; > +} > +#else > +extern int gup_huge_pd(hugepd_t hugepd, unsigned long addr, > + unsigned pdshift, unsigned long end, > + int write, struct page **pages, int *nr); > +#endif > > #define HUGETLB_ANON_FILE "anon_hugepage" > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 02d11ee..31d7fac 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1219,6 +1219,13 @@ long get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > struct vm_area_struct **vmas); > int get_user_pages_fast(unsigned long start, int nr_pages, int write, > struct page **pages); > + > +#ifdef CONFIG_HAVE_GENERIC_RCU_GUP > +extern int gup_huge_pte(pte_t orig, pte_t *ptep, unsigned long addr, > + unsigned long sz, unsigned long end, int write, > + struct page **pages, int *nr); > +#endif > + > struct kvec; > int get_kernel_pages(const struct kvec *iov, int nr_pages, int write, > struct page **pages); > diff --git a/mm/gup.c b/mm/gup.c > index cd62c8c..30773f3 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -786,65 +786,31 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, > } > #endif /* __HAVE_ARCH_PTE_SPECIAL */ > > -static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, > - unsigned long end, int write, struct page **pages, int *nr) > +int gup_huge_pte(pte_t orig, pte_t *ptep, unsigned long addr, > + unsigned long sz, unsigned long end, int write, > + struct page **pages, int *nr) > { > - struct page *head, *page, *tail; > int refs; > + unsigned long pte_end; > + struct page *head, *page, *tail; > > - if (write && !pmd_write(orig)) > - return 0; > - > - refs = 0; > - head = pmd_page(orig); > - page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); > - tail = page; > - do { > - VM_BUG_ON_PAGE(compound_head(page) != head, page); > - pages[*nr] = page; > - (*nr)++; > - page++; > - refs++; > - } while (addr += PAGE_SIZE, addr != end); > > - if (!page_cache_add_speculative(head, refs)) { > - *nr -= refs; > + if (write && !pte_write(orig)) > return 0; > - } > > - if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { > - *nr -= refs; > - while (refs--) > - put_page(head); > + if (!pte_present(orig)) > return 0; > - } > > - /* > - * Any tail pages need their mapcount reference taken before we > - * return. (This allows the THP code to bump their ref count when > - * they are split into base pages). > - */ > - while (refs--) { > - if (PageTail(tail)) > - get_huge_page_tail(tail); > - tail++; > - } > - > - return 1; > -} > - > -static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > - unsigned long end, int write, struct page **pages, int *nr) > -{ > - struct page *head, *page, *tail; > - int refs; > + pte_end = (addr + sz) & ~(sz-1); > + if (pte_end < end) > + end = pte_end; > > - if (write && !pud_write(orig)) > - return 0; > + /* hugepages are never "special" */ > + VM_BUG_ON(!pfn_valid(pte_pfn(orig))); > > refs = 0; > - head = pud_page(orig); > - page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); > + head = pte_page(orig); > + page = head + ((addr & (sz-1)) >> PAGE_SHIFT); > tail = page; > do { > VM_BUG_ON_PAGE(compound_head(page) != head, page); > @@ -859,13 +825,18 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, > return 0; > } > > - if (unlikely(pud_val(orig) != pud_val(*pudp))) { > + if (unlikely(pte_val(orig) != pte_val(*ptep))) { > *nr -= refs; > while (refs--) > put_page(head); > return 0; > } > > + /* > + * Any tail pages need their mapcount reference taken before we > + * return. (This allows the THP code to bump their ref count when > + * they are split into base pages). > + */ > while (refs--) { > if (PageTail(tail)) > get_huge_page_tail(tail); > @@ -898,10 +869,19 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, > if (pmd_numa(pmd)) > return 0; > > - if (!gup_huge_pmd(pmd, pmdp, addr, next, write, > - pages, nr)) > + if (!gup_huge_pte(__pte(pmd_val(pmd)), (pte_t *)pmdp, > + addr, PMD_SIZE, next, > + write, pages, nr)) > return 0; > > + } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) { > + /* > + * architecture have different format for hugetlbfs > + * pmd format and THP pmd format > + */ > + if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr, > + PMD_SHIFT, next, write, pages, nr)) > + return 0; > } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) > return 0; > } while (pmdp++, addr = next, addr != end); > @@ -909,22 +889,27 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, > return 1; > } The new definition of gup_huge_pte does get rid of a lot of code duplication, but it also introduces the assumption that HugeTLB pages and THPs can have their attributes referenced by pte_ accessors (rather than something like pmd_write for instance). Please add this assumption to the list in the file above. This will probably be important for pte_pfn and pte_page in case an architecture packs more attribute bits into what would normally be the lower address bits of a pte. (for arm and arm64 these bits are currently unused and expected to be zero so this code works). > > -static int gup_pud_range(pgd_t *pgdp, unsigned long addr, unsigned long end, > +static int gup_pud_range(pgd_t pgd, unsigned long addr, unsigned long end, > int write, struct page **pages, int *nr) > { > unsigned long next; > pud_t *pudp; > > - pudp = pud_offset(pgdp, addr); > + pudp = pud_offset(&pgd, addr); > do { > pud_t pud = ACCESS_ONCE(*pudp); > > next = pud_addr_end(addr, end); > if (pud_none(pud)) > return 0; > - if (pud_huge(pud)) { > - if (!gup_huge_pud(pud, pudp, addr, next, write, > - pages, nr)) > + if (unlikely(pud_huge(pud))) { > + if (!gup_huge_pte(__pte(pud_val(pud)), (pte_t *)pudp, > + addr, PUD_SIZE, next, > + write, pages, nr)) > + return 0; > + } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) { > + if (!gup_huge_pd(__hugepd(pud_val(pud)), addr, > + PUD_SHIFT, next, write, pages, nr)) > return 0; > } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) > return 0; > @@ -970,10 +955,21 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, > local_irq_save(flags); > pgdp = pgd_offset(mm, addr); > do { > + pgd_t pgd = ACCESS_ONCE(*pgdp); > + > next = pgd_addr_end(addr, end); > - if (pgd_none(*pgdp)) > + if (pgd_none(pgd)) > break; > - else if (!gup_pud_range(pgdp, addr, next, write, pages, &nr)) > + if (unlikely(pgd_huge(pgd))) { > + if (!gup_huge_pte(__pte(pgd_val(pgd)), (pte_t *)pgdp, > + addr, PGDIR_SIZE, next, > + write, pages, &nr)) > + break; > + } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) { > + if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr, > + PGDIR_SHIFT, next, write, pages, &nr)) > + break; > + } else if (!gup_pud_range(pgd, addr, next, write, pages, &nr)) > break; > } while (pgdp++, addr = next, addr != end); > local_irq_restore(flags); > @@ -1028,5 +1024,4 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write, > > return ret; > } > - > #endif /* CONFIG_HAVE_GENERIC_RCU_GUP */ > -- With the above changes (remove the arch/arm and arch/arm64 changes and add an extra assumption to the list for gup_huge_pte): Acked-by: Steve Capper Also, I've tested this on an Arndale board (arm) and a Juno board (arm64); running a custom futex on THP tail test. Cheers, -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/