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Fri, 30 Apr 2021 12:52:33 -0700 (PDT) Received: by zeus.lespinasse.org (Postfix, from userid 1000) id 88DF119F524; Fri, 30 Apr 2021 12:52:33 -0700 (PDT) From: Michel Lespinasse To: Linux-MM , Linux-Kernel Cc: Laurent Dufour , Peter Zijlstra , Michal Hocko , Matthew Wilcox , Rik van Riel , Paul McKenney , Andrew Morton , Suren Baghdasaryan , Joel Fernandes , Andy Lutomirski , Michel Lespinasse Subject: [PATCH 21/29] mm: implement speculative handling in wp_page_copy() Date: Fri, 30 Apr 2021 12:52:22 -0700 Message-Id: <20210430195232.30491-22-michel@lespinasse.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20210430195232.30491-1-michel@lespinasse.org> References: <20210430195232.30491-1-michel@lespinasse.org> MIME-Version: 1.0 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F0CA080192F0 Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=lespinasse.org header.s=srv-14-ed header.b=lXBA0+F6; dkim=pass header.d=lespinasse.org header.s=srv-14-rsa header.b=dzV0TyOI; dmarc=pass (policy=none) header.from=lespinasse.org; spf=pass (imf16.hostedemail.com: domain of walken@lespinasse.org designates 63.205.204.226 as permitted sender) smtp.mailfrom=walken@lespinasse.org X-Stat-Signature: huexyae7gj1nrkpno7i1x3mjdkof8en4 Received-SPF: none (lespinasse.org>: No applicable sender policy available) receiver=imf16; identity=mailfrom; envelope-from=""; helo=server.lespinasse.org; client-ip=63.205.204.226 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619812351-821622 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: Change wp_page_copy() to handle the speculative case. This involves aborting speculative faults if they have to allocate an anon_vma, and using pte_map_lock() instead of pte_offset_map_lock() to complete the page fault. Also change call sites to clear vmf->pte after unmapping the page table, in order to satisfy pte_map_lock()'s preconditions. Signed-off-by: Michel Lespinasse --- mm/memory.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 286776b7795b..cb66585f5145 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2928,20 +2928,27 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) pte_t entry; int page_copied = 0; struct mmu_notifier_range range; + vm_fault_t ret = VM_FAULT_OOM; - if (unlikely(anon_vma_prepare(vma))) - goto oom; + if (unlikely(!vma->anon_vma)) { + if (vmf->flags & FAULT_FLAG_SPECULATIVE) { + ret = VM_FAULT_RETRY; + goto out; + } + if (__anon_vma_prepare(vma)) + goto out; + } if (is_zero_pfn(pte_pfn(vmf->orig_pte))) { new_page = alloc_zeroed_user_highpage_movable(vma, vmf->address); if (!new_page) - goto oom; + goto out; } else { new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); if (!new_page) - goto oom; + goto out; if (!cow_user_page(new_page, old_page, vmf)) { /* @@ -2958,7 +2965,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) } if (mem_cgroup_charge(new_page, mm, GFP_KERNEL)) - goto oom_free_new; + goto out_free_new; cgroup_throttle_swaprate(new_page, GFP_KERNEL); __SetPageUptodate(new_page); @@ -2971,7 +2978,11 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) /* * Re-check the pte - we dropped the lock */ - vmf->pte = pte_offset_map_lock(mm, vmf->pmd, vmf->address, &vmf->ptl); + if (!pte_map_lock(vmf)) { + ret = VM_FAULT_RETRY; + /* put_page() will uncharge the page */ + goto out_free_new; + } if (likely(pte_same(*vmf->pte, vmf->orig_pte))) { if (old_page) { if (!PageAnon(old_page)) { @@ -3059,12 +3070,12 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf) put_page(old_page); } return page_copied ? VM_FAULT_WRITE : 0; -oom_free_new: +out_free_new: put_page(new_page); -oom: +out: if (old_page) put_page(old_page); - return VM_FAULT_OOM; + return ret; } /** @@ -3207,6 +3218,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) return wp_pfn_shared(vmf); pte_unmap_unlock(vmf->pte, vmf->ptl); + vmf->pte = NULL; return wp_page_copy(vmf); } @@ -3245,6 +3257,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) get_page(vmf->page); pte_unmap_unlock(vmf->pte, vmf->ptl); + vmf->pte = NULL; return wp_page_copy(vmf); }