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=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 18A3AC32750 for ; Fri, 2 Aug 2019 09:40:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E1E00206A2 for ; Fri, 2 Aug 2019 09:40:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564738804; bh=1cg3bNt/7VlbgSLvssmd7fmo/GrOc/mO6jNgEkCnfhw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ZO1qNXh9Pxt+gXTXxntOvSYiRYeDVzX5kkrEbhHG19voa5Rm5gwT2+BNgk8MaCuP1 9C8PXC57n20iHufbcvaR+t8jYKuMzOSuosSdDG1PNVS5RX6FG5aLklHRcuuNYC4bq7 fSJk0qEzh7oNUPQWz8WBaOoD+w3C1IE5XqiKfa80= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390428AbfHBJdL (ORCPT ); Fri, 2 Aug 2019 05:33:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:60562 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729065AbfHBJdK (ORCPT ); Fri, 2 Aug 2019 05:33:10 -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 677A0217D4; Fri, 2 Aug 2019 09:33:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564738389; bh=1cg3bNt/7VlbgSLvssmd7fmo/GrOc/mO6jNgEkCnfhw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QYEXX9r4IkZvC09ze3H+kRTbYlD6XrvFPANXFHqORTgkGDW7DhZIWabEjmMIh8h5F W2kOWt0YNv+tzhqgOMlgoN8A0JxKDkV5+BqGcYgW75H/aJ/nq/aSaFSUO/xalk7fjn NWmRVL/B1lUfE5IqYHdxmMaWt4y/Hea8O4B9hCOQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Junxiao Bi , Mike Snitzer Subject: [PATCH 4.4 085/158] dm bufio: fix deadlock with loop device Date: Fri, 2 Aug 2019 11:28:26 +0200 Message-Id: <20190802092221.576013612@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190802092203.671944552@linuxfoundation.org> References: <20190802092203.671944552@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 @@ -1561,9 +1561,7 @@ 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);