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    SubjectRe: [PATCH 1/1] block: CFQ refcounting fix
    On Wed, Aug 31 2005, Brian King wrote:
    > Jens Axboe wrote:
    > > On Tue, Aug 30 2005, wrote:
    > >
    > >>I ran across a memory leak related to the cfq scheduler. The cfq
    > >>init function increments the refcnt of the associated request_queue.
    > >>This refcount gets decremented in cfq's exit function. Since blk_cleanup_queue
    > >>only calls the elevator exit function when its refcnt goes to zero, the
    > >>request_q never gets cleaned up. It didn't look like other io schedulers were
    > >>incrementing this refcnt, so I removed the refcnt increment and it fixed the
    > >>memory leak for me.
    > >>
    > >>To reproduce the problem, simply use cfq and use the scsi_host scan sysfs
    > >>attribute to scan "- - -" repeatedly on a scsi host and watch the memory
    > >>vanish.
    > >
    > >
    > > Yeah, that actually looks like a dangling reference. I assume you tested
    > > this properly?
    > Yes. I applied the patch, booted my system (which was crashing on
    > bootup before due to out of memory errors due to the leak) ran the
    > scan a few times and verified /proc/meminfo didn't continually
    > decrease like without it, and rebooted again. If there is anything
    > else you would like me to do, I would be happy to do so.

    I think you need to remove the blk_put_queue() in cfq_put_cfqd() as
    well, otherwise I don't see how this can work without looking at freed
    memory. I'll audit the other paths as well.

    Jens Axboe

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      Last update: 2005-08-31 15:48    [W:0.020 / U:3.612 seconds]
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