From patchwork Fri Sep 20 02:21:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jia He X-Patchwork-Id: 11153713 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 93CAD195A for ; Fri, 20 Sep 2019 02:21:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6177321929 for ; Fri, 20 Sep 2019 02:21:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6177321929 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8474F8E000C; Thu, 19 Sep 2019 22:21:54 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 81D888E0003; Thu, 19 Sep 2019 22:21:54 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 70E368E000C; Thu, 19 Sep 2019 22:21:54 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0165.hostedemail.com [216.40.44.165]) by kanga.kvack.org (Postfix) with ESMTP id 4A43C8E0003 for ; Thu, 19 Sep 2019 22:21:54 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id D734F181AC9B4 for ; Fri, 20 Sep 2019 02:21:53 +0000 (UTC) X-FDA: 75953698506.17.apple46_103a8fca59459 X-Spam-Summary: 10,1,0,7e33cfe9679976f7,d41d8cd98f00b204,justin.he@arm.com,:catalin.marinas@arm.com:will@kernel.org:mark.rutland@arm.com:james.morse@arm.com:maz@kernel.org:willy@infradead.org:kirill.shutemov@linux.intel.com:linux-arm-kernel@lists.infradead.org:linux-kernel@vger.kernel.org::suzuki.poulose@arm.com:punitagrawal@gmail.com:anshuman.khandual@arm.com:yaojun8558363@gmail.com:avanbrunt@nvidia.com:robin.murphy@arm.com:tglx@linutronix.de:akpm@linux-foundation.org:jglisse@redhat.com:rcampbell@nvidia.com:hejianet@gmail.com:kaly.xin@arm.com:justin.he@arm.com,RULES_HIT:41:355:379:541:800:960:973:988:989:1260:1261:1345:1359:1437:1534:1541:1711:1730:1747:1777:1792:2393:2559:2562:3138:3139:3140:3141:3142:3352:3865:3866:3867:3868:3872:4250:5007:6119:6261:6737:6742:7903:8634:10004:11026:11473:11657:11658:11914:12043:12048:12296:12297:12438:12555:12895:13069:13221:13229:13311:13357:13523:13524:14096:14181:14384:14394:14721:21080:21451:21627:30054:30064:30090,0,RBL:217.140.110.172 :@arm.co X-HE-Tag: apple46_103a8fca59459 X-Filterd-Recvd-Size: 2915 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf03.hostedemail.com (Postfix) with ESMTP for ; Fri, 20 Sep 2019 02:21:51 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7FCAD1570; Thu, 19 Sep 2019 19:21:50 -0700 (PDT) Received: from localhost.localdomain (entos-thunderx2-02.shanghai.arm.com [10.169.40.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 0AD113F67D; Thu, 19 Sep 2019 19:21:45 -0700 (PDT) From: Jia He To: Catalin Marinas , Will Deacon , Mark Rutland , James Morse , Marc Zyngier , Matthew Wilcox , "Kirill A. Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Suzuki Poulose Cc: Punit Agrawal , Anshuman Khandual , Jun Yao , Alex Van Brunt , Robin Murphy , Thomas Gleixner , Andrew Morton , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Ralph Campbell , hejianet@gmail.com, Kaly Xin , Jia He Subject: [PATCH v6 1/3] arm64: cpufeature: introduce helper cpu_has_hw_af() Date: Fri, 20 Sep 2019 10:21:30 +0800 Message-Id: <20190920022132.149467-2-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190920022132.149467-1-justin.he@arm.com> References: <20190920022132.149467-1-justin.he@arm.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: We unconditionally set the HW_AFDBM capability and only enable it on CPUs which really have the feature. But sometimes we need to know whether this cpu has the capability of HW AF. So decouple AF from DBM by new helper cpu_has_hw_af(). Reported-by: kbuild test robot Suggested-by: Suzuki Poulose Signed-off-by: Jia He --- arch/arm64/include/asm/cpufeature.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index c96ffa4722d3..46caf934ba4e 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -667,6 +667,16 @@ static inline u32 id_aa64mmfr0_parange_to_phys_shift(int parange) default: return CONFIG_ARM64_PA_BITS; } } + +/* Decouple AF from AFDBM. */ +static inline bool cpu_has_hw_af(void) +{ + if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM)) + return read_cpuid(ID_AA64MMFR1_EL1) & 0xf; + + return false; +} + #endif /* __ASSEMBLY__ */ #endif From patchwork Fri Sep 20 02:21:31 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jia He X-Patchwork-Id: 11153715 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C030A112B for ; Fri, 20 Sep 2019 02:21:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 97EC921924 for ; Fri, 20 Sep 2019 02:21:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97EC921924 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 75C618E000D; Thu, 19 Sep 2019 22:21:57 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 7355A8E0003; Thu, 19 Sep 2019 22:21:57 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 64A498E000D; Thu, 19 Sep 2019 22:21:57 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0139.hostedemail.com [216.40.44.139]) by kanga.kvack.org (Postfix) with ESMTP id 3EFED8E0003 for ; Thu, 19 Sep 2019 22:21:57 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id E2C57181AC9B4 for ; Fri, 20 Sep 2019 02:21:56 +0000 (UTC) X-FDA: 75953698632.05.team21_10ec9caf1b307 X-Spam-Summary: 2,0,0,c636c6e16beea3d1,d41d8cd98f00b204,justin.he@arm.com,:catalin.marinas@arm.com:will@kernel.org:mark.rutland@arm.com:james.morse@arm.com:maz@kernel.org:willy@infradead.org:kirill.shutemov@linux.intel.com:linux-arm-kernel@lists.infradead.org:linux-kernel@vger.kernel.org::suzuki.poulose@arm.com:punitagrawal@gmail.com:anshuman.khandual@arm.com:yaojun8558363@gmail.com:avanbrunt@nvidia.com:robin.murphy@arm.com:tglx@linutronix.de:akpm@linux-foundation.org:jglisse@redhat.com:rcampbell@nvidia.com:hejianet@gmail.com:kaly.xin@arm.com:justin.he@arm.com,RULES_HIT:41:355:379:541:800:960:973:988:989:1260:1261:1345:1359:1437:1534:1541:1711:1730:1747:1777:1792:2393:2559:2562:2693:2901:3138:3139:3140:3141:3142:3352:3865:3867:3868:3871:3872:3874:4321:5007:6119:6261:6737:6742:7903:8634:10004:11026:11657:11658:11914:12043:12048:12114:12297:12438:12555:12895:13069:13161:13229:13311:13357:14096:14181:14384:14394:14721:21080:21451:21627:30054:30090,0,RBL:217.140.110.172:@arm.com: .lbl8.ma X-HE-Tag: team21_10ec9caf1b307 X-Filterd-Recvd-Size: 3190 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Fri, 20 Sep 2019 02:21:56 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4E37B1597; Thu, 19 Sep 2019 19:21:55 -0700 (PDT) Received: from localhost.localdomain (entos-thunderx2-02.shanghai.arm.com [10.169.40.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D6E083F67D; Thu, 19 Sep 2019 19:21:50 -0700 (PDT) From: Jia He To: Catalin Marinas , Will Deacon , Mark Rutland , James Morse , Marc Zyngier , Matthew Wilcox , "Kirill A. Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Suzuki Poulose Cc: Punit Agrawal , Anshuman Khandual , Jun Yao , Alex Van Brunt , Robin Murphy , Thomas Gleixner , Andrew Morton , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Ralph Campbell , hejianet@gmail.com, Kaly Xin , Jia He Subject: [PATCH v6 2/3] arm64: mm: implement arch_faults_on_old_pte() on arm64 Date: Fri, 20 Sep 2019 10:21:31 +0800 Message-Id: <20190920022132.149467-3-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190920022132.149467-1-justin.he@arm.com> References: <20190920022132.149467-1-justin.he@arm.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On arm64 without hardware Access Flag, copying fromuser will fail because the pte is old and cannot be marked young. So we always end up with zeroed page after fork() + CoW for pfn mappings. we don't always have a hardware-managed access flag on arm64. Hence implement arch_faults_on_old_pte on arm64 to indicate that it might cause page fault when accessing old pte. Signed-off-by: Jia He --- arch/arm64/include/asm/pgtable.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index e09760ece844..4a9939615e41 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -868,6 +868,18 @@ static inline void update_mmu_cache(struct vm_area_struct *vma, #define phys_to_ttbr(addr) (addr) #endif +/* + * On arm64 without hardware Access Flag, copying fromuser will fail because + * the pte is old and cannot be marked young. So we always end up with zeroed + * page after fork() + CoW for pfn mappings. we don't always have a + * hardware-managed access flag on arm64. + */ +static inline bool arch_faults_on_old_pte(void) +{ + return !cpu_has_hw_af(); +} +#define arch_faults_on_old_pte arch_faults_on_old_pte + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_PGTABLE_H */ From patchwork Fri Sep 20 02:21:32 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jia He X-Patchwork-Id: 11153719 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5CE8B195A for ; Fri, 20 Sep 2019 02:22:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0E14421928 for ; Fri, 20 Sep 2019 02:22:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E14421928 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 206398E000E; Thu, 19 Sep 2019 22:22:03 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id 1DD438E0003; Thu, 19 Sep 2019 22:22:03 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0F1CC8E000E; Thu, 19 Sep 2019 22:22:03 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0198.hostedemail.com [216.40.44.198]) by kanga.kvack.org (Postfix) with ESMTP id DBAD78E0003 for ; Thu, 19 Sep 2019 22:22:02 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with SMTP id 463BC181AC9B4 for ; Fri, 20 Sep 2019 02:22:02 +0000 (UTC) X-FDA: 75953698884.18.shelf86_11bc1e535392f X-Spam-Summary: 2,0,0,a2d92de918e63dba,d41d8cd98f00b204,justin.he@arm.com,:catalin.marinas@arm.com:will@kernel.org:mark.rutland@arm.com:james.morse@arm.com:maz@kernel.org:willy@infradead.org:kirill.shutemov@linux.intel.com:linux-arm-kernel@lists.infradead.org:linux-kernel@vger.kernel.org::suzuki.poulose@arm.com:punitagrawal@gmail.com:anshuman.khandual@arm.com:yaojun8558363@gmail.com:avanbrunt@nvidia.com:robin.murphy@arm.com:tglx@linutronix.de:akpm@linux-foundation.org:jglisse@redhat.com:rcampbell@nvidia.com:hejianet@gmail.com:kaly.xin@arm.com:justin.he@arm.com,RULES_HIT:2:41:355:379:541:800:960:966:967:973:988:989:1042:1260:1261:1345:1359:1437:1535:1605:1606:1730:1747:1777:1792:2196:2199:2393:2525:2559:2563:2682:2685:2693:2859:2901:2918:2933:2937:2939:2942:2945:2947:2951:2954:3022:3138:3139:3140:3141:3142:3865:3866:3867:3868:3870:3871:3872:3934:3936:3938:3941:3944:3947:3950:3953:3956:3959:4118:4321:4385:5007:6117:6119:6261:6671:6737:6742:7208:7903:8634:8660:9025:10004:11026:1 1473:116 X-HE-Tag: shelf86_11bc1e535392f X-Filterd-Recvd-Size: 7011 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Fri, 20 Sep 2019 02:22:01 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 215021570; Thu, 19 Sep 2019 19:22:00 -0700 (PDT) Received: from localhost.localdomain (entos-thunderx2-02.shanghai.arm.com [10.169.40.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id A51293F67D; Thu, 19 Sep 2019 19:21:55 -0700 (PDT) From: Jia He To: Catalin Marinas , Will Deacon , Mark Rutland , James Morse , Marc Zyngier , Matthew Wilcox , "Kirill A. Shutemov" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Suzuki Poulose Cc: Punit Agrawal , Anshuman Khandual , Jun Yao , Alex Van Brunt , Robin Murphy , Thomas Gleixner , Andrew Morton , =?utf-8?b?SsOpcsO0bWUgR2xpc3Nl?= , Ralph Campbell , hejianet@gmail.com, Kaly Xin , Jia He Subject: [PATCH v6 3/3] mm: fix double page fault on arm64 if PTE_AF is cleared Date: Fri, 20 Sep 2019 10:21:32 +0800 Message-Id: <20190920022132.149467-4-justin.he@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190920022132.149467-1-justin.he@arm.com> References: <20190920022132.149467-1-justin.he@arm.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: When we tested pmdk unit test [1] vmmalloc_fork TEST1 in arm64 guest, there will be a double page fault in __copy_from_user_inatomic of cow_user_page. Below call trace is from arm64 do_page_fault for debugging purpose [ 110.016195] Call trace: [ 110.016826] do_page_fault+0x5a4/0x690 [ 110.017812] do_mem_abort+0x50/0xb0 [ 110.018726] el1_da+0x20/0xc4 [ 110.019492] __arch_copy_from_user+0x180/0x280 [ 110.020646] do_wp_page+0xb0/0x860 [ 110.021517] __handle_mm_fault+0x994/0x1338 [ 110.022606] handle_mm_fault+0xe8/0x180 [ 110.023584] do_page_fault+0x240/0x690 [ 110.024535] do_mem_abort+0x50/0xb0 [ 110.025423] el0_da+0x20/0x24 The pte info before __copy_from_user_inatomic is (PTE_AF is cleared): [ffff9b007000] pgd=000000023d4f8003, pud=000000023da9b003, pmd=000000023d4b3003, pte=360000298607bd3 As told by Catalin: "On arm64 without hardware Access Flag, copying from user will fail because the pte is old and cannot be marked young. So we always end up with zeroed page after fork() + CoW for pfn mappings. we don't always have a hardware-managed access flag on arm64." This patch fix it by calling pte_mkyoung. Also, the parameter is changed because vmf should be passed to cow_user_page() Add a WARN_ON_ONCE when __copy_from_user_inatomic() returns error in case there can be some obscure use-case.(by Kirill) [1] https://github.com/pmem/pmdk/tree/master/src/test/vmmalloc_fork Reported-by: Yibo Cai Signed-off-by: Jia He --- mm/memory.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 59 insertions(+), 6 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index e2bb51b6242e..7c38c1ce5440 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -118,6 +118,13 @@ int randomize_va_space __read_mostly = 2; #endif +#ifndef arch_faults_on_old_pte +static inline bool arch_faults_on_old_pte(void) +{ + return false; +} +#endif + static int __init disable_randmaps(char *s) { randomize_va_space = 0; @@ -2140,8 +2147,12 @@ static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd, return same; } -static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma) +static inline int cow_user_page(struct page *dst, struct page *src, + struct vm_fault *vmf) { + struct vm_area_struct *vma = vmf->vma; + unsigned long addr = vmf->address; + debug_dma_assert_idle(src); /* @@ -2151,21 +2162,52 @@ static inline void cow_user_page(struct page *dst, struct page *src, unsigned lo * fails, we just zero-fill it. Live with it. */ if (unlikely(!src)) { - void *kaddr = kmap_atomic(dst); - void __user *uaddr = (void __user *)(va & PAGE_MASK); + void *kaddr; + void __user *uaddr = (void __user *)(addr & PAGE_MASK); + pte_t entry; + + /* On architectures with software "accessed" bits, we would + * take a double page fault, so mark it accessed here. + */ + if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) { + spin_lock(vmf->ptl); + if (likely(pte_same(*vmf->pte, vmf->orig_pte))) { + entry = pte_mkyoung(vmf->orig_pte); + if (ptep_set_access_flags(vma, addr, + vmf->pte, entry, 0)) + update_mmu_cache(vma, addr, vmf->pte); + } else { + /* Other thread has already handled the fault + * and we don't need to do anything. If it's + * not the case, the fault will be triggered + * again on the same address. + */ + spin_unlock(vmf->ptl); + return -1; + } + spin_unlock(vmf->ptl); + } + kaddr = kmap_atomic(dst); /* * This really shouldn't fail, because the page is there * in the page tables. But it might just be unreadable, * in which case we just give up and fill the result with * zeroes. */ - if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) + if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) { + /* Give a warn in case there can be some obscure + * use-case + */ + WARN_ON_ONCE(1); clear_page(kaddr); + } kunmap_atomic(kaddr); flush_dcache_page(dst); } else - copy_user_highpage(dst, src, va, vma); + copy_user_highpage(dst, src, addr, vma); + + return 0; } static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma) @@ -2318,7 +2360,16 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) vmf->address); if (!new_page) goto oom; - cow_user_page(new_page, old_page, vmf->address, vma); + + if (cow_user_page(new_page, old_page, vmf)) { + /* COW failed, if the fault was solved by other, + * it's fine. If not, userspace would re-fault on + * the same address and we will handle the fault + * from the second attempt. + */ + put_page(new_page); + goto normal; + } } if (mem_cgroup_try_charge_delay(new_page, mm, GFP_KERNEL, &memcg, false)) @@ -2420,6 +2471,8 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) } put_page(old_page); } + +normal: return page_copied ? VM_FAULT_WRITE : 0; oom_free_new: put_page(new_page);