From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933692AbdEVNg6 (ORCPT ); Mon, 22 May 2017 09:36:58 -0400 Received: from foss.arm.com ([217.140.101.70]:37296 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759855AbdEVNgy (ORCPT ); Mon, 22 May 2017 09:36:54 -0400 From: Punit Agrawal To: akpm@linux-foundation.org Cc: Punit Agrawal , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, n-horiguchi@ah.jp.nec.com, kirill.shutemov@linux.intel.com, mike.kravetz@oracle.com, steve.capper@arm.com, mark.rutland@arm.com, hillf.zj@alibaba-inc.com, linux-arch@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com, Michal Hocko Subject: [PATCH v3 2/6] mm, gup: Ensure real head page is ref-counted when using hugepages Date: Mon, 22 May 2017 14:36:00 +0100 Message-Id: <20170522133604.11392-3-punit.agrawal@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170522133604.11392-1-punit.agrawal@arm.com> References: <20170522133604.11392-1-punit.agrawal@arm.com> X-ARM-No-Footer: FoSSMail Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When speculatively taking references to a hugepage using page_cache_add_speculative() in gup_huge_pmd(), it is assumed that the page returned by pmd_page() is the head page. Although normally true, this assumption doesn't hold when the hugepage comprises of successive page table entries such as when using contiguous bit on arm64 at PTE or PMD levels. This can be addressed by ensuring that the page passed to page_cache_add_speculative() is the real head or by de-referencing the head page within the function. We take the first approach to keep the usage pattern aligned with page_cache_get_speculative() where users already pass the appropriate page, i.e., the de-referenced head. Apply the same logic to fix gup_huge_[pud|pgd]() as well. Signed-off-by: Punit Agrawal Acked-by: Steve Capper Cc: Michal Hocko Cc: "Kirill A. Shutemov" Cc: Aneesh Kumar K.V --- mm/gup.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index ccf8cb38234f..be67996513be 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1358,8 +1358,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, return __gup_device_huge_pmd(orig, addr, end, pages, nr); refs = 0; - head = pmd_page(orig); - page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1367,6 +1366,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1396,8 +1396,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, return __gup_device_huge_pud(orig, addr, end, pages, nr); refs = 0; - head = pud_page(orig); - page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1405,6 +1404,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1433,8 +1433,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, BUILD_BUG_ON(pgd_devmap(orig)); refs = 0; - head = pgd_page(orig); - page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); + page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1442,6 +1441,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; -- 2.11.0 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Punit Agrawal Subject: [PATCH v3 2/6] mm, gup: Ensure real head page is ref-counted when using hugepages Date: Mon, 22 May 2017 14:36:00 +0100 Message-ID: <20170522133604.11392-3-punit.agrawal@arm.com> References: <20170522133604.11392-1-punit.agrawal@arm.com> Return-path: In-Reply-To: <20170522133604.11392-1-punit.agrawal@arm.com> Sender: owner-linux-mm@kvack.org To: akpm@linux-foundation.org Cc: Punit Agrawal , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, n-horiguchi@ah.jp.nec.com, kirill.shutemov@linux.intel.com, mike.kravetz@oracle.com, steve.capper@arm.com, mark.rutland@arm.com, hillf.zj@alibaba-inc.com, linux-arch@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com, Michal Hocko List-Id: linux-arch.vger.kernel.org When speculatively taking references to a hugepage using page_cache_add_speculative() in gup_huge_pmd(), it is assumed that the page returned by pmd_page() is the head page. Although normally true, this assumption doesn't hold when the hugepage comprises of successive page table entries such as when using contiguous bit on arm64 at PTE or PMD levels. This can be addressed by ensuring that the page passed to page_cache_add_speculative() is the real head or by de-referencing the head page within the function. We take the first approach to keep the usage pattern aligned with page_cache_get_speculative() where users already pass the appropriate page, i.e., the de-referenced head. Apply the same logic to fix gup_huge_[pud|pgd]() as well. Signed-off-by: Punit Agrawal Acked-by: Steve Capper Cc: Michal Hocko Cc: "Kirill A. Shutemov" Cc: Aneesh Kumar K.V --- mm/gup.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index ccf8cb38234f..be67996513be 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1358,8 +1358,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, return __gup_device_huge_pmd(orig, addr, end, pages, nr); refs = 0; - head = pmd_page(orig); - page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1367,6 +1366,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1396,8 +1396,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, return __gup_device_huge_pud(orig, addr, end, pages, nr); refs = 0; - head = pud_page(orig); - page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1405,6 +1404,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1433,8 +1433,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, BUILD_BUG_ON(pgd_devmap(orig)); refs = 0; - head = pgd_page(orig); - page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); + page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1442,6 +1441,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 From: punit.agrawal@arm.com (Punit Agrawal) Date: Mon, 22 May 2017 14:36:00 +0100 Subject: [PATCH v3 2/6] mm, gup: Ensure real head page is ref-counted when using hugepages In-Reply-To: <20170522133604.11392-1-punit.agrawal@arm.com> References: <20170522133604.11392-1-punit.agrawal@arm.com> Message-ID: <20170522133604.11392-3-punit.agrawal@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org When speculatively taking references to a hugepage using page_cache_add_speculative() in gup_huge_pmd(), it is assumed that the page returned by pmd_page() is the head page. Although normally true, this assumption doesn't hold when the hugepage comprises of successive page table entries such as when using contiguous bit on arm64 at PTE or PMD levels. This can be addressed by ensuring that the page passed to page_cache_add_speculative() is the real head or by de-referencing the head page within the function. We take the first approach to keep the usage pattern aligned with page_cache_get_speculative() where users already pass the appropriate page, i.e., the de-referenced head. Apply the same logic to fix gup_huge_[pud|pgd]() as well. Signed-off-by: Punit Agrawal Acked-by: Steve Capper Cc: Michal Hocko Cc: "Kirill A. Shutemov" Cc: Aneesh Kumar K.V --- mm/gup.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index ccf8cb38234f..be67996513be 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1358,8 +1358,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, return __gup_device_huge_pmd(orig, addr, end, pages, nr); refs = 0; - head = pmd_page(orig); - page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT); + page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1367,6 +1366,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1396,8 +1396,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, return __gup_device_huge_pud(orig, addr, end, pages, nr); refs = 0; - head = pud_page(orig); - page = head + ((addr & ~PUD_MASK) >> PAGE_SHIFT); + page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1405,6 +1404,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; @@ -1433,8 +1433,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, BUILD_BUG_ON(pgd_devmap(orig)); refs = 0; - head = pgd_page(orig); - page = head + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); + page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); do { pages[*nr] = page; (*nr)++; @@ -1442,6 +1441,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, refs++; } while (addr += PAGE_SIZE, addr != end); + head = compound_head(page); if (!page_cache_add_speculative(head, refs)) { *nr -= refs; return 0; -- 2.11.0