From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7F7B5C433E1 for ; Mon, 6 Jul 2020 20:26:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4FBDE20BED for ; Mon, 6 Jul 2020 20:26:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="CCHQ/GCk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727116AbgGFU0m (ORCPT ); Mon, 6 Jul 2020 16:26:42 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:56838 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726591AbgGFU0l (ORCPT ); Mon, 6 Jul 2020 16:26:41 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 066KMV1L067944; Mon, 6 Jul 2020 20:26:25 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id : in-reply-to : references : mime-version : content-transfer-encoding; s=corp-2020-01-29; bh=7JsQApN0BMGpz+aVHeK67BKjZn8HFGP3784iAYJAa+s=; b=CCHQ/GCk3RbyK+kRfSJez25eXRWAixwDsWqZPd7anwhLc9S4NhWtAV2DWOHVrq/DKEJi yjtJJwTeQt0dVPvSDXtzw4aci1eVKg1f9P2Z1X/nx8ttJZwD6blBkspDsbyn2WZmDVWI LCNG6ByKRAhhKIu1er3int3mXm/YdbSXsGK55w9wiEK/A4NBnILg9yEIf/O7kCcPx8g/ w7DX5k6oXxRtG2M2pnbKMr5fjMfLWCyLrCCefHRrUQNJ5/MFx7uRU+lw84ZUNG9Ezwao O3j3DzgmFk8coN8NTPJFnKK8gbjMFD2HeKypjVIyYeXWG5u9l1sxQ2mFTCUDdEyNu3pj lg== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by aserp2120.oracle.com with ESMTP id 322kv68gvy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 06 Jul 2020 20:26:25 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 066KN5TV108646; Mon, 6 Jul 2020 20:26:25 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 3233p0sw4t-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 06 Jul 2020 20:26:25 +0000 Received: from abhmp0001.oracle.com (abhmp0001.oracle.com [141.146.116.7]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 066KQLgj013157; Mon, 6 Jul 2020 20:26:21 GMT Received: from monkey.oracle.com (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 06 Jul 2020 13:26:21 -0700 From: Mike Kravetz To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Michal Hocko , Hugh Dickins , Naoya Horiguchi , "Aneesh Kumar K . V" , Andrea Arcangeli , "Kirill A . Shutemov" , Davidlohr Bueso , Prakash Sangappa , Andrew Morton , Linus Torvalds , Mike Kravetz , kernel test robot Subject: [RFC PATCH 1/3] Revert: "hugetlbfs: Use i_mmap_rwsem to address page fault/truncate race" Date: Mon, 6 Jul 2020 13:26:13 -0700 Message-Id: <20200706202615.32111-2-mike.kravetz@oracle.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: <20200706202615.32111-1-mike.kravetz@oracle.com> References: <20200622005551.GK5535@shao2-debian> <20200706202615.32111-1-mike.kravetz@oracle.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9674 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 mlxlogscore=999 mlxscore=0 spamscore=0 bulkscore=0 malwarescore=0 phishscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007060138 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9674 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 bulkscore=0 malwarescore=0 suspectscore=0 mlxlogscore=999 phishscore=0 spamscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 mlxscore=0 adultscore=0 cotscore=-2147483648 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2007060138 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This reverts 87bf91d39bb52b688fb411d668fbe7df278b29ae Commit 87bf91d39bb5 depends on i_mmap_rwsem being taken during hugetlb fault processing. Commit c0d0381ade79 added code to take i_mmap_rwsem in read mode during fault processing. However, this was observed to increase fault processing time by aprox 33%. To address this, i_mmap_rwsem will only be taken during fault processing when necessary. As a result, i_mmap_rwsem can not be used to synchronize fault and truncate. In a subsequent commit, code will be added to detect the race and back out operations. Reported-by: kernel test robot Signed-off-by: Mike Kravetz --- fs/hugetlbfs/inode.c | 28 ++++++++-------------------- mm/hugetlb.c | 23 ++++++++++++----------- 2 files changed, 20 insertions(+), 31 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index ef5313f9c78f..b4bb82815dd4 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -444,9 +444,10 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end) * In this case, we first scan the range and release found pages. * After releasing pages, hugetlb_unreserve_pages cleans up region/reserv * maps and global counts. Page faults can not race with truncation - * in this routine. hugetlb_no_page() holds i_mmap_rwsem and prevents - * page faults in the truncated range by checking i_size. i_size is - * modified while holding i_mmap_rwsem. + * in this routine. hugetlb_no_page() prevents page faults in the + * truncated range. It checks i_size before allocation, and again after + * with the page table lock for the page held. The same lock must be + * acquired to unmap a page. * hole punch is indicated if end is not LLONG_MAX * In the hole punch case we scan the range and release found pages. * Only when releasing a page is the associated region/reserv map @@ -486,15 +487,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart, index = page->index; hash = hugetlb_fault_mutex_hash(mapping, index); - if (!truncate_op) { - /* - * Only need to hold the fault mutex in the - * hole punch case. This prevents races with - * page faults. Races are not possible in the - * case of truncation. - */ - mutex_lock(&hugetlb_fault_mutex_table[hash]); - } + mutex_lock(&hugetlb_fault_mutex_table[hash]); /* * If page is mapped, it was faulted in after being @@ -537,8 +530,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart, } unlock_page(page); - if (!truncate_op) - mutex_unlock(&hugetlb_fault_mutex_table[hash]); + mutex_unlock(&hugetlb_fault_mutex_table[hash]); } huge_pagevec_release(&pvec); cond_resched(); @@ -576,8 +568,8 @@ static int hugetlb_vmtruncate(struct inode *inode, loff_t offset) BUG_ON(offset & ~huge_page_mask(h)); pgoff = offset >> PAGE_SHIFT; - i_mmap_lock_write(mapping); i_size_write(inode, offset); + i_mmap_lock_write(mapping); if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)) hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0); i_mmap_unlock_write(mapping); @@ -699,11 +691,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset, /* addr is the offset within the file (zero based) */ addr = index * hpage_size; - /* - * fault mutex taken here, protects against fault path - * and hole punch. inode_lock previously taken protects - * against truncation. - */ + /* mutex taken here, fault path and hole punch */ hash = hugetlb_fault_mutex_hash(mapping, index); mutex_lock(&hugetlb_fault_mutex_table[hash]); diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 57ece74e3aae..5349beda3658 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4322,17 +4322,16 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, } /* - * We can not race with truncation due to holding i_mmap_rwsem. - * i_size is modified when holding i_mmap_rwsem, so check here - * once for faults beyond end of file. + * Use page lock to guard against racing truncation + * before we get page_table_lock. */ - size = i_size_read(mapping->host) >> huge_page_shift(h); - if (idx >= size) - goto out; - retry: page = find_lock_page(mapping, idx); if (!page) { + size = i_size_read(mapping->host) >> huge_page_shift(h); + if (idx >= size) + goto out; + /* * Check for page in userfault range */ @@ -4438,6 +4437,10 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm, } ptl = huge_pte_lock(h, mm, ptep); + size = i_size_read(mapping->host) >> huge_page_shift(h); + if (idx >= size) + goto backout; + ret = 0; if (!huge_pte_none(huge_ptep_get(ptep))) goto backout; @@ -4541,10 +4544,8 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, /* * Acquire i_mmap_rwsem before calling huge_pte_alloc and hold - * until finished with ptep. This serves two purposes: - * 1) It prevents huge_pmd_unshare from being called elsewhere - * and making the ptep no longer valid. - * 2) It synchronizes us with i_size modifications during truncation. + * until finished with ptep. This prevents huge_pmd_unshare from + * being called elsewhere and making the ptep no longer valid. * * ptep could have already be assigned via huge_pte_offset. That * is OK, as huge_pte_alloc will return the same value unless -- 2.25.4