From mboxrd@z Thu Jan 1 00:00:00 1970 From: Asias He Subject: Re: [PATCH] virtio-blk: Don't free ida when disk is in use Date: Fri, 21 Dec 2012 09:58:43 +0800 Message-ID: <50D3C253.70607@redhat.com> References: <1355946015-25879-1-git-send-email-agraf@suse.de> <20121220105417.GA3789@redhat.com> <62D6A704-CB88-4A8C-A5F3-6BD3C267895F@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <62D6A704-CB88-4A8C-A5F3-6BD3C267895F@suse.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Alexander Graf Cc: virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, "Michael S. Tsirkin" List-Id: virtualization@lists.linuxfoundation.org On 12/20/2012 07:27 PM, Alexander Graf wrote: > > On 20.12.2012, at 11:54, Michael S. Tsirkin wrote: > >> On Wed, Dec 19, 2012 at 08:40:15PM +0100, Alexander Graf wrote: >>> When a file system is mounted on a virtio-blk disk, we then remove it >>> and then reattach it, the reattached disk gets the same disk name and >>> ids as the hot removed one. >>> >>> This leads to very nasty effects - mostly rendering the newly attached >>> device completely unusable. >>> >>> Trying what happens when I do the same thing with a USB device, I saw >>> that the sd node simply doesn't get free'd when a device gets forcefully >>> removed. >>> >>> Imitate the same behavior for vd devices. This way broken vd devices >>> simply are never free'd and newly attached ones keep working just fine. >>> >>> Signed-off-by: Alexander Graf >>> --- >>> drivers/block/virtio_blk.c | 7 ++++++- >>> 1 file changed, 6 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c >>> index 0bdde8f..07a18e2 100644 >>> --- a/drivers/block/virtio_blk.c >>> +++ b/drivers/block/virtio_blk.c >>> @@ -889,6 +889,7 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) >>> { >>> struct virtio_blk *vblk = vdev->priv; >>> int index = vblk->index; >>> + int refc; >>> >>> /* Prevent config work handler from accessing the device. */ >>> mutex_lock(&vblk->config_lock); >>> @@ -903,11 +904,15 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) >>> >>> flush_work(&vblk->config_work); >>> >>> + refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount); >>> put_disk(vblk->disk); >>> mempool_destroy(vblk->pool); >>> vdev->config->del_vqs(vdev); >>> kfree(vblk); >>> - ida_simple_remove(&vd_index_ida, index); >>> + >>> + /* Only free device id if we don't have any users */ >>> + if (refc == 1) >>> + ida_simple_remove(&vd_index_ida, index); >>> } >>> >>> #ifdef CONFIG_PM >> >> Network devices take the approach of retrying every second. >> Donnu if it makes sense here. > > I would rather think the 100% right approach would be a recursive unrolling of all users bottom to top. Force unmount. Force close all fd's. I'm not sure why that doesn't happen today, but it doesn't :). Yes ;-) > > Alex > > _______________________________________________ > Virtualization mailing list > Virtualization@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/virtualization > -- Asias