Re: [PATCH 1/1] [virt] virtio-blk: Use ida to allocate disk index

On Thu, Jun 09, 2011 at 08:51:05AM +0930, Rusty Russell wrote:

On Wed, 08 Jun 2011 09:08:29 -0400, Mark Wu [off-list ref] wrote:

quoted

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 [off-list ref]
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.

I know we've tried it in the past, at the PCI device level, and ran into
some issues, but I don't remember if that code ever made it into the
mainline kernel or not.

greg k-h