From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?windows-1252?Q?Roger_Pau_Monn=E9?= Subject: Re: [PATCH] xen/blkfront: restart request queue when there is enough persistent_gnts_c Date: Fri, 9 Jan 2015 16:51:37 +0100 Message-ID: <54AFF909.3090909__14780.6184985258$1420818872$gmane$org@citrix.com> References: <1420550343-14013-1-git-send-email-bob.liu@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1420550343-14013-1-git-send-email-bob.liu@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Bob Liu , xen-devel@lists.xen.org Cc: david.vrabel@citrix.com, linux-kernel@vger.kernel.org, junxiao.bi@oracle.com List-Id: xen-devel@lists.xenproject.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.