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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 2958EC433E4 for ; Mon, 17 Aug 2020 15:23:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F014C20855 for ; Mon, 17 Aug 2020 15:22:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597677780; bh=nYm3RprnuRVhwg3iVyxfrb0xM+3RXe/tSRGDEgoHWNw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PjFZzED5xACtzluCUyi1/yirqan797jJMbwPDOUGDL8MdMIQ/aiFIuTw5o9d30el0 y3YY1c7c1m6slxP3ceL5lYMV2wnIQAOWYl9SX5gGEOcRJdqlApN/bOChG2exS1ZEzH cRiBQlrG+c9jZelukbX5/YJHWRLxbhs1kf7o/rP4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729504AbgHQPW6 (ORCPT ); Mon, 17 Aug 2020 11:22:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:45372 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729414AbgHQPWF (ORCPT ); Mon, 17 Aug 2020 11:22:05 -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 0D4C822D3E; Mon, 17 Aug 2020 15:22:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597677724; bh=nYm3RprnuRVhwg3iVyxfrb0xM+3RXe/tSRGDEgoHWNw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=w6669myVyKHEkm06SYxbHGmbCY6i2QamJjKv/EUbpPy78VhEClXV39bD5i8MZSu8y 0tjLvShWIrgwv7/Tws7ikdaPvzEMnavXlUDTLGCl0DJm3qFDxBH1zRTIDaYEsyUrWu Kg+a2oTyuqzqMRS1qskZapNdyETa/ORJ94FCLkkw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Paul E. McKenney" , Sasha Levin Subject: [PATCH 5.8 084/464] fs/btrfs: Add cond_resched() for try_release_extent_mapping() stalls Date: Mon, 17 Aug 2020 17:10:37 +0200 Message-Id: <20200817143837.809469765@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200817143833.737102804@linuxfoundation.org> References: <20200817143833.737102804@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: 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 60278e52c37ab..eeaee346f5a95 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4516,6 +4516,8 @@ int try_release_extent_mapping(struct page *page, gfp_t mask) /* once for us */ free_extent_map(em); + + cond_resched(); /* Allow large-extent preemption. */ } } return try_release_extent_state(tree, page, mask); -- 2.25.1