From patchwork Wed Mar 2 08:27:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muchun Song X-Patchwork-Id: 12765606 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 425CAC433F5 for ; Wed, 2 Mar 2022 08:30:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240170AbiCBIal (ORCPT ); Wed, 2 Mar 2022 03:30:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47276 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240173AbiCBIaf (ORCPT ); Wed, 2 Mar 2022 03:30:35 -0500 Received: from mail-pj1-x1030.google.com (mail-pj1-x1030.google.com [IPv6:2607:f8b0:4864:20::1030]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ECA6738DA7 for ; Wed, 2 Mar 2022 00:29:46 -0800 (PST) Received: by mail-pj1-x1030.google.com with SMTP id z12-20020a17090ad78c00b001bf022b69d6so22563pju.2 for ; Wed, 02 Mar 2022 00:29:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=FG/K6837zQPVwcpe+tAz7OlRAj17PMacY8wX1oMHrEs=; b=PGIGAurL4qs724ojSh6WoXxqvhMvCZBybFDAP3gGqIW/vXElNJIqLMJ/ek2d2i0/Gj DRVyI03bPjU1MyjcBUJTjfRKlpRh6REUP4Rt0TEw0TdfFlVjGLHr1ts1xWOCoIa7Z7n7 6DAdde+I05MtZqGsiYmzRKyAtq9xB1MsB6FjAP2m+1TtPnQ/DIP34Uyd2JbVYISQp65R nExPxZLC4MOYKdnifRbtN8d5JhZm/XLiy126P2Kzu2fi4yBFh+KKVB0MtSyH0tDfDene hXngnrmCnb/fLZ4hmhGh4D1wKUyfXyi/PmnXMyC3kUQnv8Nc0yCrZnmlAOgBygTB2HZu AAug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=FG/K6837zQPVwcpe+tAz7OlRAj17PMacY8wX1oMHrEs=; b=qC3yZbbr6N9yjMLSB8zfUMdg1UhCgD+qy3Bui4fLzBNr9k0KzxGQCeKqp+8lyWpril rMMH24uocHXq7B+k15aXfshQgZGuqxYYzjXLmptDCWd8D1EgZRFvt6XcjV+keCFVCUac lR4QAPlpiXHrjy/JrY30VOeUYc0cH93oaezB7M/8ole3rPVtVsxNIcb7vNBxUyoF7jy1 p7jkHcYKqNlzKwBtqoM96HFWMaYH1BpiBXeMPR6P/qNIPA4AGAHc+aIux7rg+BkSwe3U 2A20sWYwnMkKu1ihlq7xrURki3E8n6qN6OaMSGPr1NGE+cPDNyMCiC8ASz5Gg4ezZNX9 LGUw== X-Gm-Message-State: AOAM530PTjetgkggUQkhgEdSnMDKNZ08Hm5qbw76vRidiUkKdTKcF+IN pfUDY+9sgnirA1vCsI8d1otobw== X-Google-Smtp-Source: ABdhPJwPYghkWYEC4o+1xoq9Wh92BCG8knxGA3IJCRknHamVSwQdJF2a2sTBIdNnyYfvR3xQbvXLCQ== X-Received: by 2002:a17:902:e5c4:b0:151:9bf6:f47f with SMTP id u4-20020a170902e5c400b001519bf6f47fmr637485plf.110.1646209786386; Wed, 02 Mar 2022 00:29:46 -0800 (PST) Received: from FVFYT0MHHV2J.bytedance.net ([61.120.150.70]) by smtp.gmail.com with ESMTPSA id a20-20020a056a000c9400b004f396b965a9sm20922228pfv.49.2022.03.02.00.29.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Mar 2022 00:29:46 -0800 (PST) From: Muchun Song To: dan.j.williams@intel.com, willy@infradead.org, jack@suse.cz, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, apopple@nvidia.com, shy828301@gmail.com, rcampbell@nvidia.com, hughd@google.com, xiyuyang19@fudan.edu.cn, kirill.shutemov@linux.intel.com, zwisler@kernel.org, hch@infradead.org Cc: linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com, Muchun Song Subject: [PATCH v4 5/6] dax: fix missing writeprotect the pte entry Date: Wed, 2 Mar 2022 16:27:17 +0800 Message-Id: <20220302082718.32268-6-songmuchun@bytedance.com> X-Mailer: git-send-email 2.32.0 (Apple Git-132) In-Reply-To: <20220302082718.32268-1-songmuchun@bytedance.com> References: <20220302082718.32268-1-songmuchun@bytedance.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Currently dax_mapping_entry_mkclean() fails to clean and write protect the pte entry within a DAX PMD entry during an *sync operation. This can result in data loss in the following sequence: 1) process A mmap write to DAX PMD, dirtying PMD radix tree entry and making the pmd entry dirty and writeable. 2) process B mmap with the @offset (e.g. 4K) and @length (e.g. 4K) write to the same file, dirtying PMD radix tree entry (already done in 1)) and making the pte entry dirty and writeable. 3) fsync, flushing out PMD data and cleaning the radix tree entry. We currently fail to mark the pte entry as clean and write protected since the vma of process B is not covered in dax_entry_mkclean(). 4) process B writes to the pte. These don't cause any page faults since the pte entry is dirty and writeable. The radix tree entry remains clean. 5) fsync, which fails to flush the dirty PMD data because the radix tree entry was clean. 6) crash - dirty data that should have been fsync'd as part of 5) could still have been in the processor cache, and is lost. Just to use pfn_mkclean_range() to clean the pfns to fix this issue. Fixes: 4b4bb46d00b3 ("dax: clear dirty entry tags on cache flush") Signed-off-by: Muchun Song --- fs/dax.c | 83 ++++++---------------------------------------------------------- 1 file changed, 7 insertions(+), 76 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index a372304c9695..7fd4a16769f9 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #define CREATE_TRACE_POINTS @@ -789,87 +790,17 @@ static void *dax_insert_entry(struct xa_state *xas, return entry; } -static inline -unsigned long pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma) -{ - unsigned long address; - - address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); - VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma); - return address; -} - /* Walk all mappings of a given index of a file and writeprotect them */ -static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index, - unsigned long pfn) +static void dax_entry_mkclean(struct address_space *mapping, unsigned long pfn, + unsigned long npfn, pgoff_t start) { struct vm_area_struct *vma; - pte_t pte, *ptep = NULL; - pmd_t *pmdp = NULL; - spinlock_t *ptl; + pgoff_t end = start + npfn - 1; i_mmap_lock_read(mapping); - vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) { - struct mmu_notifier_range range; - unsigned long address; - + vma_interval_tree_foreach(vma, &mapping->i_mmap, start, end) { + pfn_mkclean_range(pfn, npfn, start, vma); cond_resched(); - - if (!(vma->vm_flags & VM_SHARED)) - continue; - - address = pgoff_address(index, vma); - - /* - * follow_invalidate_pte() will use the range to call - * mmu_notifier_invalidate_range_start() on our behalf before - * taking any lock. - */ - if (follow_invalidate_pte(vma->vm_mm, address, &range, &ptep, - &pmdp, &ptl)) - continue; - - /* - * No need to call mmu_notifier_invalidate_range() as we are - * downgrading page table protection not changing it to point - * to a new page. - * - * See Documentation/vm/mmu_notifier.rst - */ - if (pmdp) { -#ifdef CONFIG_FS_DAX_PMD - pmd_t pmd; - - if (pfn != pmd_pfn(*pmdp)) - goto unlock_pmd; - if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp)) - goto unlock_pmd; - - flush_cache_range(vma, address, - address + HPAGE_PMD_SIZE); - pmd = pmdp_invalidate(vma, address, pmdp); - pmd = pmd_wrprotect(pmd); - pmd = pmd_mkclean(pmd); - set_pmd_at(vma->vm_mm, address, pmdp, pmd); -unlock_pmd: -#endif - spin_unlock(ptl); - } else { - if (pfn != pte_pfn(*ptep)) - goto unlock_pte; - if (!pte_dirty(*ptep) && !pte_write(*ptep)) - goto unlock_pte; - - flush_cache_page(vma, address, pfn); - pte = ptep_clear_flush(vma, address, ptep); - pte = pte_wrprotect(pte); - pte = pte_mkclean(pte); - set_pte_at(vma->vm_mm, address, ptep, pte); -unlock_pte: - pte_unmap_unlock(ptep, ptl); - } - - mmu_notifier_invalidate_range_end(&range); } i_mmap_unlock_read(mapping); } @@ -937,7 +868,7 @@ static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev, count = 1UL << dax_entry_order(entry); index = xas->xa_index & ~(count - 1); - dax_entry_mkclean(mapping, index, pfn); + dax_entry_mkclean(mapping, pfn, count, index); dax_flush(dax_dev, page_address(pfn_to_page(pfn)), count * PAGE_SIZE); /* * After we have flushed the cache, we can clear the dirty tag. There