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=-9.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 3B5DFC34056 for ; Wed, 19 Feb 2020 21:04:23 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B84A0207FD for ; Wed, 19 Feb 2020 21:04:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="F3kXDDpZ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B84A0207FD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48N9Fc5Yr1zDqR3 for ; Thu, 20 Feb 2020 08:04:20 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=infradead.org (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org; envelope-from=willy@infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=bombadil.20170209 header.b=F3kXDDpZ; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48N99y1dYZzDqCR for ; Thu, 20 Feb 2020 08:01:07 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=xVXe2mHxuFlpJauTFAREACgBtskK8JQqv16NulPdwMo=; b=F3kXDDpZ016zj77nzf3xs9HNhB c39hgvEiXMXpDmXJJghRyVbQMd9bQMtSAzeQLHly/ybPqD2ydVSEI4rkiaB9n4MrV5lJMO5TAOHpT LsA4+sqAh3sjH6idXLPtUndMdxvuT67kL2DMo4IotYTvlEvyNqU15dBP/gmtAHMJiYi1zlhefB+pQ okljimRMCao3QCzBUAxBJQKIRfcethiQohvU/9XCsH/VS+Vpp+HAgX2+R1ONMyFmghwTrN6Tmau8B beKkIxg+LolJhz+78XZwS7VZsuxlQ7gLLHa+AyMl78a/LXsGBf7EVWA8feUeASUtSsf4m1jAST6h0 JPdvTb6Q==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j4WSv-0008Ve-Kf; Wed, 19 Feb 2020 21:01:05 +0000 From: Matthew Wilcox To: linux-fsdevel@vger.kernel.org Subject: [PATCH v7 24/24] mm: Use memalloc_nofs_save in readahead path Date: Wed, 19 Feb 2020 13:01:03 -0800 Message-Id: <20200219210103.32400-25-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200219210103.32400-1-willy@infradead.org> References: <20200219210103.32400-1-willy@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-xfs@vger.kernel.org, Michal Hocko , linux-kernel@vger.kernel.org, "Matthew Wilcox \(Oracle\)" , 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 Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" 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 bbe7208fcc2d..9fb5f77dcf69 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -22,6 +22,7 @@ #include #include #include +#include #include "internal.h" @@ -186,6 +187,18 @@ 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. */ @@ -230,6 +243,7 @@ void page_cache_readahead_unbounded(struct address_space *mapping, * will then handle the error. */ read_pages(&rac, &page_pool); + memalloc_nofs_restore(nofs); } EXPORT_SYMBOL_GPL(page_cache_readahead_unbounded); -- 2.25.0