From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751996AbaJAUY0 (ORCPT ); Wed, 1 Oct 2014 16:24:26 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:37146 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751165AbaJAUYZ (ORCPT ); Wed, 1 Oct 2014 16:24:25 -0400 Date: Wed, 1 Oct 2014 16:23:53 -0400 From: Konrad Rzeszutek Wilk To: Arianna Avanzini Cc: boris.ostrovsky@oracle.com, david.vrabel@citrix.com, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, hch@infradead.org, bob.liu@oracle.com, felipe.franciosi@citrix.com, axboe@fb.com Subject: Re: [PATCH RFC v2 5/5] xen, blkback: negotiate of the number of block rings with the frontend Message-ID: <20141001202353.GE12581@laptop.dumpdata.com> References: <1410479844-2864-1-git-send-email-avanzini.arianna@gmail.com> <1410479844-2864-6-git-send-email-avanzini.arianna@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1410479844-2864-6-git-send-email-avanzini.arianna@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Source-IP: acsinet22.oracle.com [141.146.126.238] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 12, 2014 at 01:57:24AM +0200, Arianna Avanzini wrote: > This commit lets the backend driver advertise the number of available > hardware queues; it also implements gathering from the frontend driver > the number of rings actually available for mapping. > > Signed-off-by: Arianna Avanzini > --- > drivers/block/xen-blkback/xenbus.c | 44 +++++++++++++++++++++++++++++++++++++- > 1 file changed, 43 insertions(+), 1 deletion(-) > > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c > index a4f13cc..9ff6ced 100644 > --- a/drivers/block/xen-blkback/xenbus.c > +++ b/drivers/block/xen-blkback/xenbus.c > @@ -477,6 +477,34 @@ static void xen_vbd_free(struct xen_vbd *vbd) > vbd->bdev = NULL; > } > > +static int xen_advertise_hw_queues(struct xen_blkif *blkif, > + struct request_queue *q) > +{ > + struct xen_vbd *vbd = &blkif->vbd; > + struct xenbus_transaction xbt; > + int err; > + > + if (q && q->mq_ops) > + vbd->nr_supported_hw_queues = q->nr_hw_queues; > + > + err = xenbus_transaction_start(&xbt); > + if (err) { > + BUG_ON(!blkif->be); > + xenbus_dev_fatal(blkif->be->dev, err, "starting transaction (hw queues)"); > + return err; > + } > + > + err = xenbus_printf(xbt, blkif->be->dev->nodename, "nr_supported_hw_queues", "%u", > + blkif->vbd.nr_supported_hw_queues); I would (as David had mentioned) use the same keys that netfront is using for negotiating this. Plus that means you can copy-n-paste the text from netif.h to blkif.h instead of having to write it :-) > + if (err) > + xenbus_dev_error(blkif->be->dev, err, "writing %s/nr_supported_hw_queues", > + blkif->be->dev->nodename); > + > + xenbus_transaction_end(xbt, 0); > + > + return err; > +} > + > static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, > unsigned major, unsigned minor, int readonly, > int cdrom) > @@ -484,6 +512,7 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, > struct xen_vbd *vbd; > struct block_device *bdev; > struct request_queue *q; > + int err; > > vbd = &blkif->vbd; > vbd->handle = handle; > @@ -522,6 +551,10 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, > if (q && blk_queue_secdiscard(q)) > vbd->discard_secure = true; > > + err = xen_advertise_hw_queues(blkif, q); > + if (err) > + return -ENOENT; > + > DPRINTK("Successful creation of handle=%04x (dom=%u)\n", > handle, blkif->domid); > return 0; > @@ -935,7 +968,16 @@ static int connect_ring(struct backend_info *be) > > DPRINTK("%s", dev->otherend); > > - blkif->nr_rings = 1; > + err = xenbus_gather(XBT_NIL, dev->otherend, "nr_blk_rings", > + "%u", &blkif->nr_rings, NULL); > + if (err) { > + /* > + * Frontend does not support multiqueue; force compatibility > + * mode of the driver. > + */ > + blkif->vbd.nr_supported_hw_queues = 0; > + blkif->nr_rings = 1; I would add also: pr_debug("Advertised %u queues, fronted deaf - using one ring.\n"); To make it easier during debugging/testing to figure out why the frontend does not seem to use it (and having an easy way to figure out why). > + } > > ring_ref = kzalloc(sizeof(unsigned long) * blkif->nr_rings, GFP_KERNEL); > if (!ring_ref) > -- > 2.1.0 >