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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A3CEEB64DD for ; Sun, 16 Jul 2023 20:57:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233071AbjGPU5K (ORCPT ); Sun, 16 Jul 2023 16:57:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233092AbjGPU5I (ORCPT ); Sun, 16 Jul 2023 16:57:08 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 41351109 for ; Sun, 16 Jul 2023 13:57:06 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4D6B760EBF for ; Sun, 16 Jul 2023 20:57:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 591DAC433C7; Sun, 16 Jul 2023 20:57:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689541024; bh=rIXNJXXCl8aqtP36IEA9qVnA270LaBs0WMxvif0/MHY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ii9GE1r6FPor25Xz5nirU8Iwnm+VQ8tIkY1+VObEIqSp5bLo0duL4yJ8CMP745IfU nDtJl0LJ4mKVw9GM21bngf42swbb8JnOKajJA+9/E+TQUQHeT1hYwgRWzmiamogcX+ NAkAxfHpazlNQw0UGZ1sDDb+EL0Q88xCCg1/YxRg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Darrick J. Wong" , Dave Chinner , Dave Chinner , Amir Goldstein Subject: [PATCH 6.1 572/591] xfs: explicitly specify cpu when forcing inodegc delayed work to run immediately Date: Sun, 16 Jul 2023 21:51:51 +0200 Message-ID: <20230716194938.654695582@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230716194923.861634455@linuxfoundation.org> References: <20230716194923.861634455@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: "Darrick J. Wong" commit 03e0add80f4cf3f7393edb574eeb3a89a1db7758 upstream. I've been noticing odd racing behavior in the inodegc code that could only be explained by one cpu adding an inode to its inactivation llist at the same time that another cpu is processing that cpu's llist. Preemption is disabled between get/put_cpu_ptr, so the only explanation is scheduler mayhem. I inserted the following debug code into xfs_inodegc_worker (see the next patch): ASSERT(gc->cpu == smp_processor_id()); This assertion tripped during overnight tests on the arm64 machines, but curiously not on x86_64. I think we haven't observed any resource leaks here because the lockfree list code can handle simultaneous llist_add and llist_del_all functions operating on the same list. However, the whole point of having percpu inodegc lists is to take advantage of warm memory caches by inactivating inodes on the last processor to touch the inode. The incorrect scheduling seems to occur after an inodegc worker is subjected to mod_delayed_work(). This wraps mod_delayed_work_on with WORK_CPU_UNBOUND specified as the cpu number. Unbound allows for scheduling on any cpu, not necessarily the same one that scheduled the work. Because preemption is disabled for as long as we have the gc pointer, I think it's safe to use current_cpu() (aka smp_processor_id) to queue the delayed work item on the correct cpu. Fixes: 7cf2b0f9611b ("xfs: bound maximum wait time for inodegc work") Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner Signed-off-by: Amir Goldstein Acked-by: Darrick J. Wong Signed-off-by: Greg Kroah-Hartman --- fs/xfs/xfs_icache.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/fs/xfs/xfs_icache.c +++ b/fs/xfs/xfs_icache.c @@ -2052,7 +2052,8 @@ xfs_inodegc_queue( queue_delay = 0; trace_xfs_inodegc_queue(mp, __return_address); - mod_delayed_work(mp->m_inodegc_wq, &gc->work, queue_delay); + mod_delayed_work_on(current_cpu(), mp->m_inodegc_wq, &gc->work, + queue_delay); put_cpu_ptr(gc); if (xfs_inodegc_want_flush_work(ip, items, shrinker_hits)) { @@ -2096,7 +2097,8 @@ xfs_inodegc_cpu_dead( if (xfs_is_inodegc_enabled(mp)) { trace_xfs_inodegc_queue(mp, __return_address); - mod_delayed_work(mp->m_inodegc_wq, &gc->work, 0); + mod_delayed_work_on(current_cpu(), mp->m_inodegc_wq, &gc->work, + 0); } put_cpu_ptr(gc); }