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=-10.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED 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 E7A8DC07E9C for ; Tue, 6 Jul 2021 15:14:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CFA3B61A0F for ; Tue, 6 Jul 2021 15:14:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232319AbhGFPRd (ORCPT ); Tue, 6 Jul 2021 11:17:33 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:33802 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231460AbhGFPR3 (ORCPT ); Tue, 6 Jul 2021 11:17:29 -0400 Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id E269F1FF77; Tue, 6 Jul 2021 13:52:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1625579563; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=cYuycIVYFqYGVzwo4RAZKWUEItNnBZQJ9IdSrK0ChLQ=; b=dr7bpW8S/qggHPipymiGhlkxMJxr6zmTUUbjcR4BeydH6XRuOQloHaw+MMvxMv7UaMW1rU ThJih7nK0sgpu1/tIP8uDFYW4cxVs3fpcu7NOSkKDIql2zz7m8DYK3BC6Z7PYOgvHGvXoc /Fnk1US2Tautf73WsfateZyyx86/NDc= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1625579563; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=cYuycIVYFqYGVzwo4RAZKWUEItNnBZQJ9IdSrK0ChLQ=; b=DfrcY1WXr8zkHR6AD1g3FDm4eTZBfkNbdoblYxQtC3Yj1aCX1TSwS/ictOo6VevgLCgRKa cBTEIWplvkEfDeAQ== Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap1.suse-dmz.suse.de (Postfix) with ESMTPS id 786D1133D0; Tue, 6 Jul 2021 13:52:43 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id UFlvGStg5GCPKAAAGKfGzw (envelope-from ); Tue, 06 Jul 2021 13:52:43 +0000 Received: from localhost (brahms [local]) by brahms (OpenSMTPD) with ESMTPA id 2e94826e; Tue, 6 Jul 2021 13:52:42 +0000 (UTC) From: Luis Henriques To: Jeff Layton , Ilya Dryomov Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org, Luis Henriques Subject: [PATCH v3 0/2] ceph_check_delayed_caps() softlockup Date: Tue, 6 Jul 2021 14:52:40 +0100 Message-Id: <20210706135242.9978-1-lhenriques@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * changes since v3: - always round the delay with round_jiffies_relative() in function schedule_delayed() (patch 0001) This is an attempt to fix the softlock on the delayed_work workqueue. As stated in 0002 patch: Function ceph_check_delayed_caps() is called from the mdsc->delayed_work workqueue and it can be kept looping for quite some time if caps keep being added back to the mdsc->cap_delay_list. This may result in the watchdog tainting the kernel with the softlockup flag. v2 of this fix modifies the approach by time-bounding the loop in this function, so that any caps added to the list *after* the loop starts will be postponed to the next wq run. An extra change in 0001 (suggested by Jeff) allows scheduling runs for periods smaller than the default (5 secs) period. This way, delayed_work() can have the next run scheduled for the next list element ci->i_hold_caps_max instead of 5 secs. This patchset should fix the issue reported here [1], although a quick search for "ceph_check_delayed_caps" in the tracker returns a few more bugs, possibly duplicates. [1] https://tracker.ceph.com/issues/46284 Luis Henriques (2): ceph: allow schedule_delayed() callers to set delay for workqueue ceph: reduce contention in ceph_check_delayed_caps() fs/ceph/caps.c | 17 ++++++++++++++++- fs/ceph/mds_client.c | 25 ++++++++++++++++--------- fs/ceph/super.h | 2 +- 3 files changed, 33 insertions(+), 11 deletions(-)