Messages in this thread | | | Date | Tue, 1 May 2012 11:09:06 -0700 | From | Tejun Heo <> | Subject | Re: [PATCH v3.4-rc5] block: iocontext->nr_tasks should be initialized to one |
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On Tue, May 01, 2012 at 08:02:39PM +0200, Jens Axboe wrote: > On 2012-05-01 18:17, Tejun Heo wrote: > > create_task_io_context() left ioc->nr_tasks at zero; however, a newly > > created ioc should have its nr_tasks initialized to one as it begins > > attached to the task creating it. > > > > This affects only CLONE_IO which currently doesn't seem to have any > > actual user. Sasha triggered WARN_ON_ONCE() in ioc_task_link() using > > syscall fuzzer. Even when it happens, the failure mode isn't critical > > (blk-cgroup may allow attaching a CLONE_IO'd task to a cgroup when it > > shouldn't and blkcg limits may behave weirdly). > > CLONE_IO is an exported interface, it can be set from clone(2). > Otherwise Sasha would not have hit this :-)
Yeah, but with pthread not exposing it, I'm very skeptical how much, if any, use it's getting. With its incompatibility with blk-cgroup and cfq being able to merge coop request streams, I'm not sure how much we need it. Maybe we can just make it noop?
Thanks.
-- tejun
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