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    SubjectRe: block: Check that queue is alive in blk_insert_cloned_request()
    On Mon, Jul 11 2011 at  8:52pm -0400,
    Alan Stern <stern@rowland.harvard.edu> wrote:

    > On Mon, 11 Jul 2011, Mike Snitzer wrote:
    >
    > > [cc'ing dm-devel, vivek and tejun]
    > >
    > > On Fri, Jul 8, 2011 at 7:04 PM, Roland Dreier <roland@kernel.org> wrote:
    > > > From: Roland Dreier <roland@purestorage.com>
    > > >
    > > > This fixes crashes such as the below that I see when the storage
    > > > underlying a dm-multipath device is hot-removed. ?The problem is that
    > > > dm requeues a request to a device whose block queue has already been
    > > > cleaned up, and blk_insert_cloned_request() doesn't check if the queue
    > > > is alive, but rather goes ahead and tries to queue the request. ?This
    > > > ends up dereferencing the elevator that was already freed in
    > > > blk_cleanup_queue().
    > >
    > > Your patch looks fine to me:
    > > Acked-by: Mike Snitzer <snitzer@redhat.com>
    >
    > There's still the issue that Stefan Richter pointed out: The test for a
    > dead queue must be made _after_ acquiring the queue lock, not _before_.

    Yes, quite important.

    Jens, can you tweak the patch or should Roland send a v2?


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