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Tue, 25 Feb 2020 21:48:56 GMT Received: from userp2040.oracle.com (userp2040.oracle.com [156.151.31.90]) by aserp3020.oracle.com with ESMTP id 2yd0vvs5tj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Tue, 25 Feb 2020 21:48:54 +0000 Received: from pps.filterd (userp2040.oracle.com [127.0.0.1]) by userp2040.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 01PLXUgh011068 for ; Tue, 25 Feb 2020 21:48:53 GMT Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by userp2040.oracle.com with ESMTP id 2yd6df630p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Tue, 25 Feb 2020 21:48:52 +0000 Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j6i4H-0007qB-Dl; Tue, 25 Feb 2020 21:48:41 +0000 From: Matthew Wilcox To: linux-fsdevel@vger.kernel.org Date: Tue, 25 Feb 2020 13:48:28 -0800 Message-Id: <20200225214838.30017-16-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200225214838.30017-1-willy@infradead.org> References: <20200225214838.30017-1-willy@infradead.org> MIME-Version: 1.0 X-PDR: PASS X-Source-IP: 198.137.202.133 X-ServerName: bombadil.infradead.org X-Proofpoint-SPF-Result: None X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9542 signatures=668685 X-Proofpoint-Spam-Details: rule=tap_spam_policies_notspam policy=tap_spam_policies score=0 lowpriorityscore=0 adultscore=0 bulkscore=0 impostorscore=0 mlxlogscore=562 mlxscore=0 phishscore=0 priorityscore=30 suspectscore=1 spamscore=0 malwarescore=0 clxscore=212 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002250151 X-Spam: Clean X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 phishscore=0 bulkscore=0 suspectscore=1 spamscore=0 malwarescore=0 adultscore=0 mlxlogscore=768 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002250151 Cc: linux-xfs@vger.kernel.org, Michal Hocko , linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-mm@kvack.org, ocfs2-devel@oss.oracle.com, Cong Wang , linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Subject: [Ocfs2-devel] [PATCH v8 15/25] mm: Use memalloc_nofs_save in readahead path X-BeenThere: ocfs2-devel@oss.oracle.com X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9542 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 bulkscore=0 mlxlogscore=999 malwarescore=0 adultscore=0 phishscore=0 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002250151 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9542 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 lowpriorityscore=0 malwarescore=0 impostorscore=0 suspectscore=0 priorityscore=1501 phishscore=0 clxscore=1034 mlxlogscore=999 spamscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002250151 From: "Matthew Wilcox (Oracle)" Ensure that memory allocations in the readahead path do not attempt to reclaim file-backed pages, which could lead to a deadlock. It is possible, though unlikely this is the root cause of a problem observed by Cong Wang. Signed-off-by: Matthew Wilcox (Oracle) Reported-by: Cong Wang Suggested-by: Michal Hocko --- mm/readahead.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/mm/readahead.c b/mm/readahead.c index 0afb55a49909..7f2d54fb1691 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -22,6 +22,7 @@ #include #include #include +#include #include "internal.h" @@ -185,6 +186,18 @@ void page_cache_readahead_unbounded(struct address_space *mapping, }; unsigned long i; + /* + * Partway through the readahead operation, we will have added + * locked pages to the page cache, but will not yet have submitted + * them for I/O. Adding another page may need to allocate memory, + * which can trigger memory reclaim. Telling the VM we're in + * the middle of a filesystem operation will cause it to not + * touch file-backed pages, preventing a deadlock. Most (all?) + * filesystems already specify __GFP_NOFS in their mapping's + * gfp_mask, but let's be explicit here. + */ + unsigned int nofs = memalloc_nofs_save(); + /* * Preallocate as many pages as we will need. */ @@ -229,6 +242,7 @@ void page_cache_readahead_unbounded(struct address_space *mapping, * will then handle the error. */ read_pages(&rac, &page_pool, false); + memalloc_nofs_restore(nofs); } EXPORT_SYMBOL_GPL(page_cache_readahead_unbounded);