From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757572AbbAIPvn (ORCPT ); Fri, 9 Jan 2015 10:51:43 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:60493 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752192AbbAIPvl (ORCPT ); Fri, 9 Jan 2015 10:51:41 -0500 X-IronPort-AV: E=Sophos;i="5.07,731,1413244800"; d="scan'208";a="214080532" Message-ID: <54AFF909.3090909@citrix.com> Date: Fri, 9 Jan 2015 16:51:37 +0100 From: =?windows-1252?Q?Roger_Pau_Monn=E9?= User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Bob Liu , CC: , , , Subject: Re: [PATCH] xen/blkfront: restart request queue when there is enough persistent_gnts_c References: <1420550343-14013-1-git-send-email-bob.liu@oracle.com> In-Reply-To: <1420550343-14013-1-git-send-email-bob.liu@oracle.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org El 06/01/15 a les 14.19, Bob Liu ha escrit: > When there is no enough free grants, gnttab_alloc_grant_references() > will fail and block request queue will stop. > If the system is always lack of grants, blkif_restart_queue_callback() can't be > scheduled and block request queue can't be restart(block I/O hang). > > But when there are former requests complete, some grants may free to > persistent_gnts_c, we can give the request queue another chance to restart and > avoid block hang. > > Reported-by: Junxiao Bi > Signed-off-by: Bob Liu > --- > drivers/block/xen-blkfront.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index 2236c6f..dd30f99 100644 > --- a/drivers/block/xen-blkfront.c > +++ b/drivers/block/xen-blkfront.c > @@ -1125,6 +1125,17 @@ static void blkif_completion(struct blk_shadow *s, struct blkfront_info *info, > } > } > } > + > + /* > + * Request queue would be stopped if failed to alloc enough grants and > + * won't be restarted until gnttab_free_count >= info->callback->count. > + * > + * But there is another case, once we have enough persistent grants we > + * can try to restart the request queue instead of continue to wait for > + * 'gnttab_free_count'. > + */ > + if (info->persistent_gnts_c >= info->callback.count) > + schedule_work(&info->work); I guess I'm missing something here, but blkif_completion is called by blkif_interrupt, which in turn calls kick_pending_request_queues when finished, which IMHO should be enough to restart the processing of requests. Roger.