| Message ID | 151043109938.2842.14834662818213616199.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sat, 11 Nov 2017, Dan Williams wrote: > Currently only get_user_pages_fast() can safely handle the writable gup > case due to its use of pud_access_permitted() to check whether the pud > entry is writable. In the gup slow path pud_write() is used instead of > pud_access_permitted() and to date it has been unimplemented, just calls > BUG_ON(). > > kernel BUG at ./include/linux/hugetlb.h:244! > [..] > RIP: 0010:follow_devmap_pud+0x482/0x490 > [..] > Call Trace: > follow_page_mask+0x28c/0x6e0 > __get_user_pages+0xe4/0x6c0 > get_user_pages_unlocked+0x130/0x1b0 > get_user_pages_fast+0x89/0xb0 > iov_iter_get_pages_alloc+0x114/0x4a0 > nfs_direct_read_schedule_iovec+0xd2/0x350 > ? nfs_start_io_direct+0x63/0x70 > nfs_file_direct_read+0x1e0/0x250 > nfs_file_read+0x90/0xc0 > > For now this just implements a simple check for the _PAGE_RW bit similar > to pmd_write. However, this implies that the gup-slow-path check is > missing the extra checks that the gup-fast-path performs with > pud_access_permitted. Later patches will align all checks to use the > 'access_permitted' helper if the architecture provides it. Note that the > generic 'access_permitted' helper fallback is the simple _PAGE_RW check > on architectures that do not define the 'access_permitted' helper(s). > > Fixes: a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent hugepages") > Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Dave Hansen <dave.hansen@intel.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: <stable@vger.kernel.org> > Cc: <x86@kernel.org> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > --- > arch/arm64/include/asm/pgtable.h | 1 + > arch/sparc/include/asm/pgtable_64.h | 1 + > arch/x86/include/asm/pgtable.h | 6 ++++++ For the x86 part: Acked-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index b46e54c2399b..9a943792a823 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -340,6 +340,7 @@ static inline int pmd_protnone(pmd_t pmd) #define pfn_pmd(pfn,prot) (__pmd(((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))) #define mk_pmd(page,prot) pfn_pmd(page_to_pfn(page),prot) +#define __HAVE_ARCH_PUD_WRITE #define pud_write(pud) pte_write(pud_pte(pud)) #define pud_pfn(pud) (((pud_val(pud) & PUD_MASK) & PHYS_MASK) >> PAGE_SHIFT) diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h index fd9d9bac7cfa..bcf54a9cf6c5 100644 --- a/arch/sparc/include/asm/pgtable_64.h +++ b/arch/sparc/include/asm/pgtable_64.h @@ -693,6 +693,7 @@ static inline unsigned long pmd_write(pmd_t pmd) return pte_write(pte); } +#define __HAVE_ARCH_PUD_WRITE #define pud_write(pud) pte_write(__pte(pud_val(pud))) #ifdef CONFIG_TRANSPARENT_HUGEPAGE diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index f735c3016325..5c396724fd0d 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1093,6 +1093,12 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, clear_bit(_PAGE_BIT_RW, (unsigned long *)pmdp); } +#define __HAVE_ARCH_PUD_WRITE +static inline int pud_write(pud_t pud) +{ + return pud_flags(pud) & _PAGE_RW; +} + /* * clone_pgd_range(pgd_t *dst, pgd_t *src, int count); * diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 757dc6ffc7ba..bd738624bd16 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -812,6 +812,15 @@ static inline int pmd_write(pmd_t pmd) return 0; } #endif /* __HAVE_ARCH_PMD_WRITE */ + +#ifndef __HAVE_ARCH_PUD_WRITE +static inline int pud_write(pud_t pud) +{ + BUG(); + return 0; +} +#endif /* __HAVE_ARCH_PUD_WRITE */ + #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #if !defined(CONFIG_TRANSPARENT_HUGEPAGE) || \ diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index fbf5b31d47ee..82a25880714a 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -239,14 +239,6 @@ static inline int pgd_write(pgd_t pgd) } #endif -#ifndef pud_write -static inline int pud_write(pud_t pud) -{ - BUG(); - return 0; -} -#endif - #define HUGETLB_ANON_FILE "anon_hugepage" enum {
Currently only get_user_pages_fast() can safely handle the writable gup case due to its use of pud_access_permitted() to check whether the pud entry is writable. In the gup slow path pud_write() is used instead of pud_access_permitted() and to date it has been unimplemented, just calls BUG_ON(). kernel BUG at ./include/linux/hugetlb.h:244! [..] RIP: 0010:follow_devmap_pud+0x482/0x490 [..] Call Trace: follow_page_mask+0x28c/0x6e0 __get_user_pages+0xe4/0x6c0 get_user_pages_unlocked+0x130/0x1b0 get_user_pages_fast+0x89/0xb0 iov_iter_get_pages_alloc+0x114/0x4a0 nfs_direct_read_schedule_iovec+0xd2/0x350 ? nfs_start_io_direct+0x63/0x70 nfs_file_direct_read+0x1e0/0x250 nfs_file_read+0x90/0xc0 For now this just implements a simple check for the _PAGE_RW bit similar to pmd_write. However, this implies that the gup-slow-path check is missing the extra checks that the gup-fast-path performs with pud_access_permitted. Later patches will align all checks to use the 'access_permitted' helper if the architecture provides it. Note that the generic 'access_permitted' helper fallback is the simple _PAGE_RW check on architectures that do not define the 'access_permitted' helper(s). Fixes: a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent hugepages") Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Will Deacon <will.deacon@arm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: <stable@vger.kernel.org> Cc: <x86@kernel.org> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- arch/arm64/include/asm/pgtable.h | 1 + arch/sparc/include/asm/pgtable_64.h | 1 + arch/x86/include/asm/pgtable.h | 6 ++++++ include/asm-generic/pgtable.h | 9 +++++++++ include/linux/hugetlb.h | 8 -------- 5 files changed, 17 insertions(+), 8 deletions(-)