From patchwork Wed Feb 2 14:33:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Muchun Song X-Patchwork-Id: 12733084 Received: from mail-pl1-f170.google.com (mail-pl1-f170.google.com [209.85.214.170]) (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 048CC2F29 for ; Wed, 2 Feb 2022 14:34:54 +0000 (UTC) Received: by mail-pl1-f170.google.com with SMTP id l13so9772629plg.9 for ; Wed, 02 Feb 2022 06:34:53 -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=uplRDMf9P3k9aUR6OrL9VGZsCccO7/3RG36fBhJFyME=; b=kSLOTeQhvBFw7fsL96na0cRlWcVjElWVvAoseaINB/pZHqA7KWxP3av/18pkL1aF+0 MKOQJZSHRAd5a5PwAiR1h2yWe05lQOOjIoyguZQ6FRdfPhWOhYS2Q2cmjxo/HRQGt/Jy BLny0ZANjrtCry2BJhLKzk1uwsIbJqH7I0w5IgRmX7/Xh8uBWszfMynYBEc3fqos21Qu CxFcpkYtSGBHbUPVu/D5nyQUIrxpb/JUykO56+48bAqzUjS16agFbbk3P3Z3QbATWhrM WyboLCUgxUOu26c9aIeOzVgtlweBJ8PzLJ1+xwkL63Hi5ucGoWjq0bEicpnPVjxdUrpG lkKw== 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=uplRDMf9P3k9aUR6OrL9VGZsCccO7/3RG36fBhJFyME=; b=SeySM7jEQhhBDlOCIHTKLPrpufoLyZmzu9Uh6u6yCJxO6RyQTC43Ou+sa3DfvDdEHn nIDUfg/qnsT45srcmCsMYuR5AQBZ3tiJHvbBUx49FwBAZMCNf9O5MYhpG0o/FDmN6qMe vgu+mo08Xia+VesCY85XZ8n95IeryaMIirVgamWos6Lmknw8u12jobpEdAtJSO1NCGAU w1QPl+RKHNubGChQHopn/RSN+mKoDyo8h8feiCHOE4dke2wUo1fN61gUtXtvWZibRhhl ukuFJCI5JQvbrxEjWem69a3EfKOWBLp8VoURSdA6263A+5926aVjmaHqn+Ww/DfYgwFZ MuTA== X-Gm-Message-State: AOAM5315+JMFgura7OSyTQqIgbcWqg2LYR3a3Ut4pxq89M5prQj08//B amKtcrfRSkHNBSyPwyO+3T8Hvg== X-Google-Smtp-Source: ABdhPJxYVhkrB3EfA0Rf/jBLdL6J+MWAJGy/3N8zt0fObDKgb6hfYJaRk8Ro75dji+V85rbzZGD4sA== X-Received: by 2002:a17:902:e851:: with SMTP id t17mr30063915plg.102.1643812493488; Wed, 02 Feb 2022 06:34:53 -0800 (PST) Received: from FVFYT0MHHV2J.tiktokcdn.com ([139.177.225.241]) by smtp.gmail.com with ESMTPSA id s9sm29079268pgm.76.2022.02.02.06.34.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Feb 2022 06:34:53 -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, Muchun Song Subject: [PATCH v2 5/6] dax: fix missing writeprotect the pte entry Date: Wed, 2 Feb 2022 22:33:06 +0800 Message-Id: <20220202143307.96282-6-songmuchun@bytedance.com> X-Mailer: git-send-email 2.32.0 (Apple Git-132) In-Reply-To: <20220202143307.96282-1-songmuchun@bytedance.com> References: <20220202143307.96282-1-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 --- fs/dax.c | 83 ++++++---------------------------------------------------------- 1 file changed, 7 insertions(+), 76 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index e031e4b6c13c..b64ac02d55d7 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #define CREATE_TRACE_POINTS @@ -801,87 +802,17 @@ 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); } @@ -949,7 +880,7 @@ 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