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[198.145.29.99]) by mx.google.com with ESMTPS id n3si9814164pgh.53.2019.06.01.06.22.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 01 Jun 2019 06:22:35 -0700 (PDT) Received-SPF: pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=wHZUqz32; spf=pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sashal@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id BF97126E87; Sat, 1 Jun 2019 13:22:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559395354; bh=gOZxUIYQsBEQRv9bk+M8JatOYaVu6PBPjijotTiPsns=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wHZUqz32iMTPY1jA7ax4RY3fenLrXNAdaQmzNdANUaF0MH+Fi4Wbf/8ckv3ikjlzu +dIh+cdEP31vBOn84qlvACNtF+M1OInnwSmhPHsvChVfKw9Cw5UdERLv5Vc4lchfq9 Iuw1+lrUeqVnQd3Dk8m3pMCZgbFaqveG6y9Glk/4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Aneesh Kumar K.V" , Andrew Morton , Dan Williams , Andrea Arcangeli , Linus Torvalds , Sasha Levin , linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-mm@kvack.org Subject: [PATCH AUTOSEL 4.19 013/141] mm: page_mkclean vs MADV_DONTNEED race Date: Sat, 1 Jun 2019 09:19:49 -0400 Message-Id: <20190601132158.25821-13-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190601132158.25821-1-sashal@kernel.org> References: <20190601132158.25821-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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: From: "Aneesh Kumar K.V" [ Upstream commit 024eee0e83f0df52317be607ca521e0fc572aa07 ] MADV_DONTNEED is handled with mmap_sem taken in read mode. We call page_mkclean without holding mmap_sem. MADV_DONTNEED implies that pages in the region are unmapped and subsequent access to the pages in that range is handled as a new page fault. This implies that if we don't have parallel access to the region when MADV_DONTNEED is run we expect those range to be unallocated. w.r.t page_mkclean() we need to make sure that we don't break the MADV_DONTNEED semantics. MADV_DONTNEED check for pmd_none without holding pmd_lock. This implies we skip the pmd if we temporarily mark pmd none. Avoid doing that while marking the page clean. Keep the sequence same for dax too even though we don't support MADV_DONTNEED for dax mapping The bug was noticed by code review and I didn't observe any failures w.r.t test run. This is similar to commit 58ceeb6bec86d9140f9d91d71a710e963523d063 Author: Kirill A. Shutemov Date: Thu Apr 13 14:56:26 2017 -0700 thp: fix MADV_DONTNEED vs. MADV_FREE race commit ced108037c2aa542b3ed8b7afd1576064ad1362a Author: Kirill A. Shutemov Date: Thu Apr 13 14:56:20 2017 -0700 thp: fix MADV_DONTNEED vs. numa balancing race Link: http://lkml.kernel.org/r/20190321040610.14226-1-aneesh.kumar@linux.ibm.com Signed-off-by: Aneesh Kumar K.V Reviewed-by: Andrew Morton Cc: Dan Williams Cc:"Kirill A . Shutemov" Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- fs/dax.c | 2 +- mm/rmap.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 004c8ac1117c4..75a289c31c7e5 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -908,7 +908,7 @@ static void dax_mapping_entry_mkclean(struct address_space *mapping, goto unlock_pmd; flush_cache_page(vma, address, pfn); - pmd = pmdp_huge_clear_flush(vma, address, pmdp); + pmd = pmdp_invalidate(vma, address, pmdp); pmd = pmd_wrprotect(pmd); pmd = pmd_mkclean(pmd); set_pmd_at(vma->vm_mm, address, pmdp, pmd); diff --git a/mm/rmap.c b/mm/rmap.c index 85b7f94233526..f048c2651954b 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -926,7 +926,7 @@ static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma, continue; flush_cache_page(vma, address, page_to_pfn(page)); - entry = pmdp_huge_clear_flush(vma, address, pmd); + entry = pmdp_invalidate(vma, address, pmd); entry = pmd_wrprotect(entry); entry = pmd_mkclean(entry); set_pmd_at(vma->vm_mm, address, pmd, entry); -- 2.20.1