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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 C794FC2B9F4 for ; Tue, 22 Jun 2021 12:40:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A62B160FF2 for ; Tue, 22 Jun 2021 12:40:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231644AbhFVMm5 (ORCPT ); Tue, 22 Jun 2021 08:42:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:52413 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229999AbhFVMl2 (ORCPT ); Tue, 22 Jun 2021 08:41:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1624365552; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ya5yyWfTX8+CsAsj4fkti9KQ8++ZtmpTifiRu8lZnfE=; b=NKrgjaVTzWr61i7afM3UTZiElTyd4qRxJEXvMqQVhQTOkC6cXre9buZxa/hm58MPCGzMH1 kcpywcjGQQyyO06OsNutP8ERD/OwtHD7qVg51nocsyojAWkCl0DexSZEQ8ge5l9cU6B6cw JizDISD1Vb0gdij9jNjLgPlAt1zhmmQ= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-115-RiMWcvy6MP-wRRYXXaPnDQ-1; Tue, 22 Jun 2021 08:39:10 -0400 X-MC-Unique: RiMWcvy6MP-wRRYXXaPnDQ-1 Received: by mail-qk1-f197.google.com with SMTP id t131-20020a37aa890000b02903a9f6c1e8bfso17812973qke.10 for ; Tue, 22 Jun 2021 05:39:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=ya5yyWfTX8+CsAsj4fkti9KQ8++ZtmpTifiRu8lZnfE=; b=EyC7gPaWbmjUKqTtuebT237+qZiEOLmW0bUP14lhSBn/Zxbn80JJZ/OXF4UgvCXIOV KIDrzLocgWkDtIgCCB8AbQ9boR5AA160zo6UMN2gZ5Db/VZCm1qhCnbWTTrg6aKiXj/x T4yZApK+vLUGz9F7qy4MlUmEDzxIj8tj1LE67N+h/FfVxCwqRf9UWajGlbDkIVJCTFS1 1UUHjy8V6EyTKhMl3vZk6ZMWkh9miY7/QI77mSHNT62LNa5DijCGKaVs5G8CK2zyIxxl 0wOWS8x0FWSuOy2/Adkr6WvfDNlocwdQuBAADud9/WpS73rz/EPHU1EjTHivTNrmFlL3 iobw== X-Gm-Message-State: AOAM533NBDavmGCA6QeDQFSntV+Bialuigqiel96K4+5nnRLPvZZqjxq ZQ6op5w7FcJGsVLjy4oLgWjr2OKZGNqgKJYc9Oa3xasWR4NxmpO9IvNgVaop/992oqeqlK6oq+o 1wISuIRcr14cjNsfOb9sR X-Received: by 2002:ac8:43cc:: with SMTP id w12mr3228317qtn.137.1624365549882; Tue, 22 Jun 2021 05:39:09 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzbfEJNz+1oPlQuu/rRkZ3CB9fowsJdmNZrqGeKU87mHAh2skfneeyNrC3ESv+A50O1p8ov8g== X-Received: by 2002:ac8:43cc:: with SMTP id w12mr3228298qtn.137.1624365549696; Tue, 22 Jun 2021 05:39:09 -0700 (PDT) Received: from bfoster ([98.216.211.229]) by smtp.gmail.com with ESMTPSA id m11sm1543418qtn.81.2021.06.22.05.39.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Jun 2021 05:39:09 -0700 (PDT) Date: Tue, 22 Jun 2021 08:39:07 -0400 From: Brian Foster To: Dave Chinner Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 2/4] xfs: remove callback dequeue loop from xlog_state_do_iclog_callbacks Message-ID: References: <20210622040604.1290539-1-david@fromorbit.com> <20210622040604.1290539-3-david@fromorbit.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210622040604.1290539-3-david@fromorbit.com> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Tue, Jun 22, 2021 at 02:06:02PM +1000, Dave Chinner wrote: > From: Dave Chinner > > If we are processing callbacks on an iclog, nothing can be > concurrently adding callbacks to the loop. We only add callbacks to > the iclog when they are in ACTIVE or WANT_SYNC state, and we > explicitly do not add callbacks if the iclog is already in IOERROR > state. > > The only way to have a dequeue racing with an enqueue is to be > processing a shutdown without a direct reference to an iclog in > ACTIVE or WANT_SYNC state. As the enqueue avoids this race > condition, we only ever need a single dequeue operation in > xlog_state_do_iclog_callbacks(). Hence we can remove the loop. > This sort of relates to my question on the previous patch.. > Signed-off-by: Dave Chinner > --- Reviewed-by: Brian Foster > fs/xfs/xfs_log.c | 16 ++++++---------- > 1 file changed, 6 insertions(+), 10 deletions(-) > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > index bb4390942275..05b00fa4d661 100644 > --- a/fs/xfs/xfs_log.c > +++ b/fs/xfs/xfs_log.c > @@ -2774,19 +2774,15 @@ xlog_state_do_iclog_callbacks( > struct xlog *log, > struct xlog_in_core *iclog) > { > - trace_xlog_iclog_callbacks_start(iclog, _RET_IP_); > - spin_lock(&iclog->ic_callback_lock); > - while (!list_empty(&iclog->ic_callbacks)) { > - LIST_HEAD(tmp); > + LIST_HEAD(tmp); > > - list_splice_init(&iclog->ic_callbacks, &tmp); > - > - spin_unlock(&iclog->ic_callback_lock); > - xlog_cil_process_committed(&tmp); > - spin_lock(&iclog->ic_callback_lock); > - } > + trace_xlog_iclog_callbacks_start(iclog, _RET_IP_); > > + spin_lock(&iclog->ic_callback_lock); > + list_splice_init(&iclog->ic_callbacks, &tmp); > spin_unlock(&iclog->ic_callback_lock); > + > + xlog_cil_process_committed(&tmp); > trace_xlog_iclog_callbacks_done(iclog, _RET_IP_); > } > > -- > 2.31.1 >