Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754301Ab1DKQ7c (ORCPT ); Mon, 11 Apr 2011 12:59:32 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:56713 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754158Ab1DKQ71 (ORCPT ); Mon, 11 Apr 2011 12:59:27 -0400 Date: Mon, 11 Apr 2011 12:59:23 -0400 From: "hch@infradead.org" To: NeilBrown Cc: Mike Snitzer , Jens Axboe , "linux-kernel@vger.kernel.org" , "hch@infradead.org" , dm-devel@redhat.com, linux-raid@vger.kernel.org Subject: Re: [PATCH 05/10] block: remove per-queue plugging Message-ID: <20110411165923.GA15442@infradead.org> References: <1295659049-2688-6-git-send-email-jaxboe@fusionio.com> <20110303221353.GA10366@redhat.com> <4D761E0D.8050200@fusionio.com> <20110308202100.GA31744@redhat.com> <4D76912C.9040705@fusionio.com> <20110308220526.GA393@redhat.com> <20110310005810.GA17911@redhat.com> <20110405130541.6c2b5f86@notabene.brown> <20110411145022.710c30e9@notabene.brown> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110411145022.710c30e9@notabene.brown> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1337 Lines: 38 On Mon, Apr 11, 2011 at 02:50:22PM +1000, NeilBrown wrote: > diff --git a/block/blk-core.c b/block/blk-core.c > index 273d60b..903ce8d 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -2674,19 +2674,23 @@ static void flush_plug_list(struct blk_plug *plug) > struct request_queue *q; > unsigned long flags; > struct request *rq; > + struct list_head head; > > BUG_ON(plug->magic != PLUG_MAGIC); > > if (list_empty(&plug->list)) > return; > + list_add(&head, &plug->list); > + list_del_init(&plug->list); > > if (plug->should_sort) > - list_sort(NULL, &plug->list, plug_rq_cmp); > + list_sort(NULL, &head, plug_rq_cmp); > + plug->should_sort = 0; As Jens mentioned this should be list_splice_init. But looking over flush_plug_list the code there seems strange to me. What does the local_irq_save in flush_plug_list protect? Why don't we need it over the list_sort? And do we still need it when first splicing the list to a local one? It's one of these cases where I'd really like to see more comments explaining why the code is doing what it's doing. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/