From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757053Ab1FIKlN (ORCPT ); Thu, 9 Jun 2011 06:41:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64153 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753591Ab1FIKlL (ORCPT ); Thu, 9 Jun 2011 06:41:11 -0400 Message-ID: <4DF0A374.6090504@redhat.com> Date: Thu, 09 Jun 2011 06:41:56 -0400 From: Mark Wu User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110419 Red Hat/3.1.10-1.el6_0 Lightning/1.0b2 Thunderbird/3.1.10 MIME-Version: 1.0 To: Rusty Russell CC: Tejun Heo , "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Jens Axboe , Greg Kroah-Hartman Subject: Re: [PATCH 1/1] [virt] virtio-blk: Use ida to allocate disk index References: <1306913069-23637-1-git-send-email-dwu@redhat.com> <87mxi1xfz0.fsf@rustcorp.com.au> <4DEF744D.9040702@redhat.com> <87mxhrgba6.fsf@rustcorp.com.au> <20110609091433.GB11773@htj.dyndns.org> In-Reply-To: <20110609091433.GB11773@htj.dyndns.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/09/2011 05:14 AM, Tejun Heo wrote: > Hello, > > On Thu, Jun 09, 2011 at 08:51:05AM +0930, Rusty Russell wrote: >> On Wed, 08 Jun 2011 09:08:29 -0400, Mark Wu wrote: >>> Hi Rusty, >>> Yes, I can't figure out an instance of disk probing in parallel either, but as >>> per the following commit, I think we still need use lock for safety. What's your opinion? >>> >>> commit 4034cc68157bfa0b6622efe368488d3d3e20f4e6 >>> Author: Tejun Heo >>> Date: Sat Feb 21 11:04:45 2009 +0900 >>> >>> [SCSI] sd: revive sd_index_lock >>> >>> Commit f27bac2761cab5a2e212dea602d22457a9aa6943 which converted sd to >>> use ida instead of idr incorrectly removed sd_index_lock around id >>> allocation and free. idr/ida do have internal locks but they protect >>> their free object lists not the allocation itself. The caller is >>> responsible for that. This missing synchronization led to the same id >>> being assigned to multiple devices leading to oops. >> >> I'm confused. Tejun, Greg, anyone can probes happen in parallel? >> >> If so, I'll have to review all my drivers. > > Unless async is explicitly used, probe happens sequentially. IOW, if > there's no async_schedule() call, things won't happen in parallel. > That said, I think it wouldn't be such a bad idea to protect ida with > spinlock regardless unless the probe code explicitly requires > serialization. > > Thanks. > Since virtio blk driver doesn't use async probe, it needn't use spinlock to protect ida. So remove the lock from patch. >>From fbb396df9dbf8023f1b268be01b43529a3993d57 Mon Sep 17 00:00:00 2001 From: Mark Wu Date: Thu, 9 Jun 2011 06:34:07 -0400 Subject: [PATCH 1/1] [virt] virtio-blk: Use ida to allocate disk index Current index allocation in virtio-blk is based on a monotonically increasing variable "index". It could cause some confusion about disk name in the case of hot-plugging disks. And it's impossible to find the lowest available index by just maintaining a simple index. So it's changed to use ida to allocate index via referring to the index allocation in scsi disk. Signed-off-by: Mark Wu --- drivers/block/virtio_blk.c | 28 +++++++++++++++++++++++----- 1 files changed, 23 insertions(+), 5 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 079c088..bf81ab6 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -8,10 +8,13 @@ #include #include #include +#include #define PART_BITS 4 -static int major, index; +static int major; +static DEFINE_IDA(vd_index_ida); + struct workqueue_struct *virtblk_wq; struct virtio_blk @@ -23,6 +26,7 @@ struct virtio_blk /* The disk structure for the kernel. */ struct gendisk *disk; + u32 index; /* Request tracking. */ struct list_head reqs; @@ -343,12 +347,23 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) struct request_queue *q; int err; u64 cap; - u32 v, blk_size, sg_elems, opt_io_size; + u32 v, blk_size, sg_elems, opt_io_size, index; u16 min_io_size; u8 physical_block_exp, alignment_offset; - if (index_to_minor(index) >= 1 << MINORBITS) - return -ENOSPC; + do { + if (!ida_pre_get(&vd_index_ida, GFP_KERNEL)) + return -ENOMEM; + err = ida_get_new(&vd_index_ida, &index); + } while (err == -EAGAIN); + + if (err) + return err; + + if (index_to_minor(index) >= 1 << MINORBITS) { + err = -ENOSPC; + goto out_free_index; + } /* We need to know how many segments before we allocate. */ err = virtio_config_val(vdev, VIRTIO_BLK_F_SEG_MAX, @@ -421,7 +436,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev) vblk->disk->private_data = vblk; vblk->disk->fops = &virtblk_fops; vblk->disk->driverfs_dev = &vdev->dev; - index++; + vblk->index = index; /* configure queue flush support */ if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH)) @@ -516,6 +531,8 @@ out_free_vq: vdev->config->del_vqs(vdev); out_free_vblk: kfree(vblk); +out_free_index: + ida_remove(&vd_index_ida, index); out: return err; } @@ -538,6 +555,7 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) mempool_destroy(vblk->pool); vdev->config->del_vqs(vdev); kfree(vblk); + ida_remove(&vd_index_ida, vblk->index); } static const struct virtio_device_id id_table[] = { -- 1.7.1