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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 24F99C76186 for ; Mon, 29 Jul 2019 19:32:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E55B1217D7 for ; Mon, 29 Jul 2019 19:32:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564428768; bh=QbL9JCURI8IT0HneOsq6UcX7QVgG1PIUGLeYwf0lED4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=n27HW4lKQJB5ScjhtmLXd9CVW7TV/GIWC45bkA7gONa82lTBw026zEXfjeI/2g3rF U2R43rIXig8bfbMxCcWG6VSkpE8J3fl/lZenbA0d9nNfo6zjXKuuDOfQSBUi9AITVf SDluK0/4SMcobpPsugEhU3fDMa/9WRfQLPbQHxuQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730277AbfG2Tcq (ORCPT ); Mon, 29 Jul 2019 15:32:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:46348 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729647AbfG2Tcn (ORCPT ); Mon, 29 Jul 2019 15:32:43 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4A4DE217D6; Mon, 29 Jul 2019 19:32:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564428761; bh=QbL9JCURI8IT0HneOsq6UcX7QVgG1PIUGLeYwf0lED4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2lhmOhKpm0i6WptHkgAFHP223C4/1iwi5Fs7VkFPgnKyhtcwGOGFjEb5JsTK7zSc/ DJU/oZCDfgD/ejwTwTmvvydJEI/MvRWf7oXjujl/+3SgQ2ibKmwA0q9CZAsNFBDizt AiKdjkR3gxQesmp4vRTDs6EorxPHhdAxznwDWvF0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Junxiao Bi , Mike Snitzer Subject: [PATCH 4.14 177/293] dm bufio: fix deadlock with loop device Date: Mon, 29 Jul 2019 21:21:08 +0200 Message-Id: <20190729190838.077796168@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190729190820.321094988@linuxfoundation.org> References: <20190729190820.321094988@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Junxiao Bi commit bd293d071ffe65e645b4d8104f9d8fe15ea13862 upstream. When thin-volume is built on loop device, if available memory is low, the following deadlock can be triggered: One process P1 allocates memory with GFP_FS flag, direct alloc fails, memory reclaim invokes memory shrinker in dm_bufio, dm_bufio_shrink_scan() runs, mutex dm_bufio_client->lock is acquired, then P1 waits for dm_buffer IO to complete in __try_evict_buffer(). But this IO may never complete if issued to an underlying loop device that forwards it using direct-IO, which allocates memory using GFP_KERNEL (see: do_blockdev_direct_IO()). If allocation fails, memory reclaim will invoke memory shrinker in dm_bufio, dm_bufio_shrink_scan() will be invoked, and since the mutex is already held by P1 the loop thread will hang, and IO will never complete. Resulting in ABBA deadlock. Cc: stable@vger.kernel.org Signed-off-by: Junxiao Bi Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-bufio.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -1630,9 +1630,7 @@ dm_bufio_shrink_scan(struct shrinker *sh unsigned long freed; c = container_of(shrink, struct dm_bufio_client, shrinker); - if (sc->gfp_mask & __GFP_FS) - dm_bufio_lock(c); - else if (!dm_bufio_trylock(c)) + if (!dm_bufio_trylock(c)) return SHRINK_STOP; freed = __scan(c, sc->nr_to_scan, sc->gfp_mask);