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SubjectRe: [PATCH 1/1] [virt] virtio-blk: Use ida to allocate disk index
On 06/02/2011 06:34 AM, Michael S. Tsirkin wrote:
> On Wed, Jun 01, 2011 at 04:25:48AM -0400, Mark Wu wrote:
>> On 06/01/2011 03:24 AM, Mark Wu wrote:
>>> - if (index_to_minor(index)>= 1<< MINORBITS)
>>> - return -ENOSPC;
>>> + do {
>>> + if (!ida_pre_get(&vd_index_ida, GFP_KERNEL))
>>> + return err;
>>> +
>> There's a problem in above code: err is not initialized before
>> using, so change it to return -1;
>> + do {
>> + if (!ida_pre_get(&vd_index_ida, GFP_KERNEL))
>> + return -1;
>
> Not -1. Pls return -ENOMEM.
>
> --
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Hi Michael,
Thanks for pointing out that. This is the revised patch.


From ffe49efd20938952a09d5a87fe694a6f62937756 Mon Sep 17 00:00:00 2001
From: Mark Wu <dwu@redhat.com>
Date: Wed, 8 Jun 2011 08:25:53 -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 <dwu@redhat.com>
---
drivers/block/virtio_blk.c | 37 ++++++++++++++++++++++++++++++++-----
1 files changed, 32 insertions(+), 5 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 079c088..f13b758 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -8,10 +8,14 @@
#include <linux/scatterlist.h>
#include <linux/string_helpers.h>
#include <scsi/scsi_cmnd.h>
+#include <linux/idr.h>

#define PART_BITS 4

-static int major, index;
+static int major;
+static DEFINE_SPINLOCK(vd_index_lock);
+static DEFINE_IDA(vd_index_ida);
+
struct workqueue_struct *virtblk_wq;

struct virtio_blk
@@ -23,6 +27,7 @@ struct virtio_blk

/* The disk structure for the kernel. */
struct gendisk *disk;
+ u32 index;

/* Request tracking. */
struct list_head reqs;
@@ -343,12 +348,26 @@ 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;
+
+ spin_lock(&vd_index_lock);
+ err = ida_get_new(&vd_index_ida, &index);
+ spin_unlock(&vd_index_lock);
+ } 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 +440,7 @@ 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 +535,10 @@ out_free_vq:
vdev->config->del_vqs(vdev);
out_free_vblk:
kfree(vblk);
+out_free_index:
+ spin_lock(&vd_index_lock);
+ ida_remove(&vd_index_ida, index);
+ spin_unlock(&vd_index_lock);
out:
return err;
}
@@ -538,6 +561,10 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
mempool_destroy(vblk->pool);
vdev->config->del_vqs(vdev);
kfree(vblk);
+
+ spin_lock(&vd_index_lock);
+ ida_remove(&vd_index_ida, vblk->index);
+ spin_unlock(&vd_index_lock);
}

static const struct virtio_device_id id_table[] = {
--
1.7.1

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