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    SubjectRe: [PATCH 0/1] aoe: ensure we initialise the request_queue correctly
    On Mon, 24 August 2009 Ed Cashin <ecashin@coraid.com> wrote:
    > On Fri Aug 21 12:41:59 EDT 2009, apw@canonical.com wrote:
    > > We have been seeing oopses in very recent kernels when using the
    > > AOE driver. When attempting to mount remote devices we get a
    > > warning from the kobject layer:
    > >
    > > [ 2645.959090] kobject '<NULL>' (ffff880059ca22c0): tried to add
    > > an uninitialized object, something is seriously wrong.
    > >
    > > Looking at the driver it seems to have always had an embedded
    > > request_queue and it is this that is throwing the error. It
    > > appears the intent is tha these would be allocated and released
    > > using helpers, and the lack of these leaves the object
    > > uninitialised and throws the error. It is unclear how this could
    > > ever have worked.
    >
    > This aoe driver does not handle I/O requests but provides its own
    > make_request function to blk_queue_make_request and handles bios
    > instead.
    >
    > The reason I was interested in a git bisect is that I suspect that
    > before nobody was interested in the request_queue in the aoe driver
    > until recent changes to kobject code. A couple people have indicated
    > that they'd be doing such a git bisect, so if anybody has done that,
    > please Cc me.
    >
    I finished bisecting the NULL object and ended up at this commit:
    cd43e26f071524647e660706b784ebcbefbd2e44

    block: Expose stacked device queues in sysfs

    Currently stacking devices do not have a queue directory in sysfs.
    However, many of the I/O characteristics like sector size, maximum
    request size, etc. are queue properties.

    This patch enables the queue directory for MD/DM devices. The elevator
    code has been modified to deal with queues that do not have an I/O
    scheduler.

    Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>


    This seems to generate /sys/block/$device/queue and its contents for
    everyone who is using queues, not just for those queues that have a
    non-NULL queue->request_fn.

    Bruno


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