From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752207AbcGSAh0 (ORCPT ); Mon, 18 Jul 2016 20:37:26 -0400 Received: from mail-pa0-f68.google.com ([209.85.220.68]:33878 "EHLO mail-pa0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751930AbcGSAhY (ORCPT ); Mon, 18 Jul 2016 20:37:24 -0400 From: Minfei Huang X-Google-Original-From: Minfei Huang Date: Tue, 19 Jul 2016 08:37:15 +0800 To: Cornelia Huck Cc: Minfei Huang , mst@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, fanc.fnst@cn.fujitsu.com, Minfei Huang Subject: Re: [PATCH v2] virtio_blk: Fix a slient kernel panic Message-ID: <20160719003715.GA41853@MinfeideMacBook-Pro.local> References: <1468850489-40157-1-git-send-email-mnghuan@gmail.com> <20160718172128.5b8c10b1.cornelia.huck@de.ibm.com> <20160718160421.GA20047@huangminfeis-MacBook-Pro.local> <20160718182534.7b0bdfe9.cornelia.huck@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160718182534.7b0bdfe9.cornelia.huck@de.ibm.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/18/16 at 06:25P, Cornelia Huck wrote: > On Tue, 19 Jul 2016 00:18:32 +0800 > Minfei Huang wrote: > > > On 07/18/16 at 05:21P, Cornelia Huck wrote: > > > On Mon, 18 Jul 2016 22:01:29 +0800 > > > Minfei Huang wrote: > > > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > > > index 42758b5..d920512 100644 > > > > --- a/drivers/block/virtio_blk.c > > > > +++ b/drivers/block/virtio_blk.c > > > > @@ -381,9 +381,9 @@ static int init_vq(struct virtio_blk *vblk) > > > > { > > > > int err = 0; > > > > int i; > > > > - vq_callback_t **callbacks; > > > > - const char **names; > > > > - struct virtqueue **vqs; > > > > + vq_callback_t **callbacks = NULL; > > > > + const char **names = NULL; > > > > + struct virtqueue **vqs = NULL; > > > > > > If you init the variables to NULL anyway... > > > > Hi, Cornelia. > > > > Thanks for reviewing this patch. > > > > Seems there is no need to init these variables to NULL. I will remove > > them laster. > > Fine with me. > > > > > > > > > > unsigned short num_vqs; > > > > struct virtio_device *vdev = vblk->vdev; > > > > > > > > @@ -394,22 +394,16 @@ static int init_vq(struct virtio_blk *vblk) > > > > num_vqs = 1; > > > > > > > > > > ...just do > > > > > > err = -ENOMEM; > > > > > > here and... > > > > > > > vblk->vqs = kmalloc(sizeof(*vblk->vqs) * num_vqs, GFP_KERNEL); > > > > - if (!vblk->vqs) { > > > > - err = -ENOMEM; > > > > - goto out; > > > > - } > > > > + if (!vblk->vqs) > > > > + return -ENOMEM; > > > > > > > > names = kmalloc(sizeof(*names) * num_vqs, GFP_KERNEL); > > > > - if (!names) > > > > - goto err_names; > > > > - > > > > callbacks = kmalloc(sizeof(*callbacks) * num_vqs, GFP_KERNEL); > > > > - if (!callbacks) > > > > - goto err_callbacks; > > > > - > > > > vqs = kmalloc(sizeof(*vqs) * num_vqs, GFP_KERNEL); > > > > - if (!vqs) > > > > - goto err_vqs; > > > > + if (!names || !callbacks || !vqs) { > > > > + err = -ENOMEM; > > > > + goto out; > > > > + } > > > > > > ...you could use the > > > > > > foo = kmalloc(...); > > > if (!foo) > > > goto out; > > > > > > sequence in any case. This avoids trying again and again if e.g. the > > > names allocation already failed. > > > > For this implementation, I have referred others which calls > > vdev->config->find_vqs as well. Yes, this continues trying to allocate > > memory, although memory allocation failed before. > > It might not be the best idea, though; although it should hopefully be > a not-so-common occurrence. Yep, for that memont, there is enough memory to be allocated. > > > > > > > > > Alternatively, you should be fine if you don't init the variables to > > > NULL: The code is now either taking an early exit or setting all of the > > > variables anyway. > > > > > > > It's a big change if we refactor the helper ->find_vqs, since other > > devices also call it. > > Actually, I was referring to not initializing the variables to NULL in > this function and keeping the rest of your changes: IOW, just what you > suggested above :) Ok. I will repost an update to fix it. Thanks Minfei >