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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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