From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752589Ab2LSUPv (ORCPT ); Wed, 19 Dec 2012 15:15:51 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:35382 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751342Ab2LSUPo (ORCPT ); Wed, 19 Dec 2012 15:15:44 -0500 Date: Wed, 19 Dec 2012 15:14:48 -0500 From: Konrad Rzeszutek Wilk To: Jan Beulich Cc: Olaf Hering , xen-devel@lists.xen.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] xen/blkback: prevent repeated backend_changed invocations Message-ID: <20121219201448.GH15037@phenom.dumpdata.com> References: <1355259026-16946-1-git-send-email-olaf@aepfle.de> <50C9FC0302000078000B0344@nat28.tlf.novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50C9FC0302000078000B0344@nat28.tlf.novell.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 13, 2012 at 03:02:11PM +0000, Jan Beulich wrote: > >>> On 11.12.12 at 21:50, Olaf Hering wrote: > > backend_changed might be called multiple times, which will leak > > be->mode. Make sure it will be called only once. Remove some unneeded > > checks. Also the be->mode string was leaked, release the memory on > > device shutdown. > > So I decided to make an attempt myself, retaining the current > behavior of allowing multiple calls, yet not having to sprinkle > around multiple kfree()-s for be->mode. Slightly re-structuring > the function made this pretty strait forward. Would it be possible to post a patch? > > Jan > > > Signed-off-by: Olaf Hering > > --- > > > > incorporate all comments from Jan. > > fold the oneline change to xen_blkbk_remove into this change > > now its compile tested. > > > > drivers/block/xen-blkback/xenbus.c | 69 ++++++++++++++++++-------------------- > > 1 file changed, 33 insertions(+), 36 deletions(-) > > > > diff --git a/drivers/block/xen-blkback/xenbus.c > > b/drivers/block/xen-blkback/xenbus.c > > index f58434c..5ca77c3 100644 > > --- a/drivers/block/xen-blkback/xenbus.c > > +++ b/drivers/block/xen-blkback/xenbus.c > > @@ -28,6 +28,7 @@ struct backend_info { > > unsigned major; > > unsigned minor; > > char *mode; > > + unsigned alive; > > }; > > > > static struct kmem_cache *xen_blkif_cachep; > > @@ -366,6 +367,7 @@ static int xen_blkbk_remove(struct xenbus_device *dev) > > be->blkif = NULL; > > } > > > > + kfree(be->mode); > > kfree(be); > > dev_set_drvdata(&dev->dev, NULL); > > return 0; > > @@ -501,10 +503,14 @@ static void backend_changed(struct xenbus_watch *watch, > > = container_of(watch, struct backend_info, backend_watch); > > struct xenbus_device *dev = be->dev; > > int cdrom = 0; > > - char *device_type; > > + char *device_type, *p; > > + long handle; > > > > DPRINTK(""); > > > > + if (be->alive) > > + return; > > + > > err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x", > > &major, &minor); > > if (XENBUS_EXIST_ERR(err)) { > > @@ -520,12 +526,7 @@ static void backend_changed(struct xenbus_watch *watch, > > return; > > } > > > > - if ((be->major || be->minor) && > > - ((be->major != major) || (be->minor != minor))) { > > - pr_warn(DRV_PFX "changing physical device (from %x:%x to %x:%x) not > > supported.\n", > > - be->major, be->minor, major, minor); > > - return; > > - } > > + be->alive = 1; > > > > be->mode = xenbus_read(XBT_NIL, dev->nodename, "mode", NULL); > > if (IS_ERR(be->mode)) { > > @@ -541,39 +542,35 @@ static void backend_changed(struct xenbus_watch *watch, > > kfree(device_type); > > } > > > > - if (be->major == 0 && be->minor == 0) { > > - /* Front end dir is a number, which is used as the handle. */ > > - > > - char *p = strrchr(dev->otherend, '/') + 1; > > - long handle; > > - err = strict_strtoul(p, 0, &handle); > > - if (err) > > - return; > > - > > - be->major = major; > > - be->minor = minor; > > + /* Front end dir is a number, which is used as the handle. */ > > + p = strrchr(dev->otherend, '/') + 1; > > + err = strict_strtoul(p, 0, &handle); > > + if (err) > > + return; > > > > - err = xen_vbd_create(be->blkif, handle, major, minor, > > - (NULL == strchr(be->mode, 'w')), cdrom); > > - if (err) { > > - be->major = 0; > > - be->minor = 0; > > - xenbus_dev_fatal(dev, err, "creating vbd structure"); > > - return; > > - } > > + be->major = major; > > + be->minor = minor; > > > > - err = xenvbd_sysfs_addif(dev); > > - if (err) { > > - xen_vbd_free(&be->blkif->vbd); > > - be->major = 0; > > - be->minor = 0; > > - xenbus_dev_fatal(dev, err, "creating sysfs entries"); > > - return; > > - } > > + err = xen_vbd_create(be->blkif, handle, major, minor, > > + (NULL == strchr(be->mode, 'w')), cdrom); > > + if (err) { > > + be->major = 0; > > + be->minor = 0; > > + xenbus_dev_fatal(dev, err, "creating vbd structure"); > > + return; > > + } > > > > - /* We're potentially connected now */ > > - xen_update_blkif_status(be->blkif); > > + err = xenvbd_sysfs_addif(dev); > > + if (err) { > > + xen_vbd_free(&be->blkif->vbd); > > + be->major = 0; > > + be->minor = 0; > > + xenbus_dev_fatal(dev, err, "creating sysfs entries"); > > + return; > > } > > + > > + /* We're potentially connected now */ > > + xen_update_blkif_status(be->blkif); > > } > > > > > > -- > > 1.8.0.1 > >