From patchwork Sun Apr 3 05:39:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muchun Song X-Patchwork-Id: 12799477 Received: from mail-pl1-f181.google.com (mail-pl1-f181.google.com [209.85.214.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4F3331FBD for ; Sun, 3 Apr 2022 05:41:46 +0000 (UTC) Received: by mail-pl1-f181.google.com with SMTP id p17so5685950plo.9 for ; Sat, 02 Apr 2022 22:41:46 -0700 (PDT) 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=ij9Ou9wostYj6EGhx1lGIRtlvYKIpDSow4S1vsu6OkU=; b=XeDR2vJSmU7Ivd3WN7rCTrbkf25VSpqOphH+Y0b8v30A2+sw5zqGls9Infj7s8yVlP svWNwaO1p/aGhXjj7Zupj5x3tuNFjanAQWQWM6u7liBIOurPY1rHvAScK/VCuZ7iFAfg pFi84i3m4JempmgKh34P9NIz6wJ875JOw+0Aqg1U6aRUn/Xtf4315rOLnph7LcPVNo/o bCkdnwqsmM4WrVRAFJEPnNeFpXgXWQf43xph7Siue3ttUD6DaIe9v5c5W0aQH8CZed+l DJeXFlvu8ihwu8DuH0KCvDNYmwo5uFWXXWrAhMpb9CnbUIRuHIanH9teTlUUk6AjPz45 B+cw== 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=ij9Ou9wostYj6EGhx1lGIRtlvYKIpDSow4S1vsu6OkU=; b=0+qjfFarey+rOrwYGAl7uNEyHPOx76+MWi9ZHLIYbVy4Os2gOTVfM6y5vxLguxLnXY Sq2cpwoCoRDWUgf+7aJ1PbiWk/gtyFDQPr2zQD3GsPF+fFUBmvo5riW3hySFKh7rCvDr jv2/60rff+J0/KWivKmfwdrVgTrUg2wAE93n8LJ2D37YtY2hoeF3rDZReeQNZ3EnrGtN b6qAOddMljlLy7dbUlKKv5OjWk9P9PHL8arZE+r/f0MEaHlDDfHelIdvboqNjk7dreBU gshqWBHpQri6EjlkQprD4ik7FVTMsUVSXTHF/td1GkBG/jQCmnF1WIvVvKyxeV9iT0uP BJ9w== X-Gm-Message-State: AOAM5334qpaU6jzxGV23zdRHVgM1JnCrukimDI4z1Aw2nQbSHpBl9Gbd k4iiutL7HiwxV+ugkzlEn1+O8w== X-Google-Smtp-Source: ABdhPJxCMZdeA2cMPE4dzvOrFTBRiMQzhbgxuHDpUKbgulRM1aIbxvU3i75LzfHUzm2CYnokBq58DQ== X-Received: by 2002:a17:902:dad0:b0:154:740a:9094 with SMTP id q16-20020a170902dad000b00154740a9094mr17337374plx.107.1648964505726; Sat, 02 Apr 2022 22:41:45 -0700 (PDT) Received: from FVFYT0MHHV2J.bytedance.net ([139.177.225.245]) by smtp.gmail.com with ESMTPSA id a38-20020a056a001d2600b004f70d5e92basm8262479pfx.34.2022.04.02.22.41.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 02 Apr 2022 22:41:45 -0700 (PDT) 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 , Christoph Hellwig Subject: [PATCH v7 5/6] dax: fix missing writeprotect the pte entry Date: Sun, 3 Apr 2022 13:39:56 +0800 Message-Id: <20220403053957.10770-6-songmuchun@bytedance.com> X-Mailer: git-send-email 2.32.0 (Apple Git-132) In-Reply-To: <20220403053957.10770-1-songmuchun@bytedance.com> References: <20220403053957.10770-1-songmuchun@bytedance.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 Reviewed-by: Christoph Hellwig --- fs/dax.c | 99 ++++++++-------------------------------------------------------- 1 file changed, 12 insertions(+), 87 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index a372304c9695..1ac12e877f4f 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #define CREATE_TRACE_POINTS @@ -789,96 +790,12 @@ 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) -{ - struct vm_area_struct *vma; - pte_t pte, *ptep = NULL; - pmd_t *pmdp = NULL; - spinlock_t *ptl; - - i_mmap_lock_read(mapping); - vma_interval_tree_foreach(vma, &mapping->i_mmap, index, index) { - struct mmu_notifier_range range; - unsigned long address; - - 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); -} - static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev, struct address_space *mapping, void *entry) { - unsigned long pfn, index, count; + unsigned long pfn, index, count, end; long ret = 0; + struct vm_area_struct *vma; /* * A page got tagged dirty in DAX mapping? Something is seriously @@ -936,8 +853,16 @@ static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev, pfn = dax_to_pfn(entry); count = 1UL << dax_entry_order(entry); index = xas->xa_index & ~(count - 1); + end = index + count - 1; + + /* Walk all mappings of a given index of a file and writeprotect them */ + i_mmap_lock_read(mapping); + vma_interval_tree_foreach(vma, &mapping->i_mmap, index, end) { + pfn_mkclean_range(pfn, count, index, vma); + cond_resched(); + } + i_mmap_unlock_read(mapping); - dax_entry_mkclean(mapping, index, pfn); 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