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blkio-throttle: Fix possible multiplication overflow in iops calculations
o User can specify max iops value of 32bit (UINT_MAX), through cgroup interface. If a user has specified say 4294967294 (UNIT_MAX - 2), then on 32bit platform, following multiplication can overflow. io_allowed = (tg->iops[rw] * jiffy_elapsed_rnd) o Explicitly cast the multiplication to 64bit and then perform division and then check whether result is still great then UNINT_MAX. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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@ -430,6 +430,7 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
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bool rw = bio_data_dir(bio);
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unsigned int io_allowed;
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unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
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u64 tmp;
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jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
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@ -439,7 +440,20 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
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jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
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io_allowed = (tg->iops[rw] * jiffy_elapsed_rnd) / HZ;
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/*
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* jiffy_elapsed_rnd should not be a big value as minimum iops can be
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* 1 then at max jiffy elapsed should be equivalent of 1 second as we
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* will allow dispatch after 1 second and after that slice should
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* have been trimmed.
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*/
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tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
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do_div(tmp, HZ);
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if (tmp > UINT_MAX)
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io_allowed = UINT_MAX;
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else
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io_allowed = tmp;
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if (tg->io_disp[rw] + 1 <= io_allowed) {
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if (wait)
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