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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,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 DEF26C433E0 for ; Mon, 10 Aug 2020 19:20:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD3D522BF3 for ; Mon, 10 Aug 2020 19:20:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597087233; bh=4yLMnPaJzotJ8TahdzZXIXI6kUMopCupuwA2zHxLxVc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Gjf+7QJtijuxeoHTl3QMz5TWw85P/laDYGKH64bn4YghbMgSB3ajNTXwpQiqcesNy 95/uZiZCVYqNrmRUzJw3UyOpDdugoUiZmlsMmL72Rfzw+12lX7nMizjVbfEUEIcgo3 AuxT+3eXgJJFVNR1ZcbfAwj7IkRwzME/+i4vpbSM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730314AbgHJTUc (ORCPT ); Mon, 10 Aug 2020 15:20:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:45226 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729864AbgHJTNu (ORCPT ); Mon, 10 Aug 2020 15:13:50 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D75A822B47; Mon, 10 Aug 2020 19:13:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597086829; bh=4yLMnPaJzotJ8TahdzZXIXI6kUMopCupuwA2zHxLxVc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EVV3y+IwRT73zwMt4R4ZeI6NE2+CAwS8vxgKm+6aRZXT9nHgiSn5uV81TasYqpl+c OoQP3/Jepw4/nCdJ/hx6HN+fkqvxNByn+JLYzlwB4eyIX1hUX8cXxsPtOXLOq6KQC6 Bn/WhtLeeArrKZGDLzF8wXFovHIv/31UqvXYDD3M= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paul E. McKenney" , Sasha Levin , linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 03/22] fs/btrfs: Add cond_resched() for try_release_extent_mapping() stalls Date: Mon, 10 Aug 2020 15:13:25 -0400 Message-Id: <20200810191345.3795166-3-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200810191345.3795166-1-sashal@kernel.org> References: <20200810191345.3795166-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" [ Upstream commit 9f47eb5461aaeb6cb8696f9d11503ae90e4d5cb0 ] Very large I/Os can cause the following RCU CPU stall warning: RIP: 0010:rb_prev+0x8/0x50 Code: 49 89 c0 49 89 d1 48 89 c2 48 89 f8 e9 e5 fd ff ff 4c 89 48 10 c3 4c = 89 06 c3 4c 89 40 10 c3 0f 1f 00 48 8b 0f 48 39 cf 74 38 <48> 8b 47 10 48 85 c0 74 22 48 8b 50 08 48 85 d2 74 0c 48 89 d0 48 RSP: 0018:ffffc9002212bab0 EFLAGS: 00000287 ORIG_RAX: ffffffffffffff13 RAX: ffff888821f93630 RBX: ffff888821f93630 RCX: ffff888821f937e0 RDX: 0000000000000000 RSI: 0000000000102000 RDI: ffff888821f93630 RBP: 0000000000103000 R08: 000000000006c000 R09: 0000000000000238 R10: 0000000000102fff R11: ffffc9002212bac8 R12: 0000000000000001 R13: ffffffffffffffff R14: 0000000000102000 R15: ffff888821f937e0 __lookup_extent_mapping+0xa0/0x110 try_release_extent_mapping+0xdc/0x220 btrfs_releasepage+0x45/0x70 shrink_page_list+0xa39/0xb30 shrink_inactive_list+0x18f/0x3b0 shrink_lruvec+0x38e/0x6b0 shrink_node+0x14d/0x690 do_try_to_free_pages+0xc6/0x3e0 try_to_free_mem_cgroup_pages+0xe6/0x1e0 reclaim_high.constprop.73+0x87/0xc0 mem_cgroup_handle_over_high+0x66/0x150 exit_to_usermode_loop+0x82/0xd0 do_syscall_64+0xd4/0x100 entry_SYSCALL_64_after_hwframe+0x44/0xa9 On a PREEMPT=n kernel, the try_release_extent_mapping() function's "while" loop might run for a very long time on a large I/O. This commit therefore adds a cond_resched() to this loop, providing RCU any needed quiescent states. Signed-off-by: Paul E. McKenney Signed-off-by: Sasha Levin --- fs/btrfs/extent_io.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 6d2bfbb63d9ba..ef1fd6a09d8e5 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4323,6 +4323,8 @@ int try_release_extent_mapping(struct extent_map_tree *map, /* once for us */ free_extent_map(em); + + cond_resched(); /* Allow large-extent preemption. */ } } return try_release_extent_state(map, tree, page, mask); -- 2.25.1