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| author | Vivek Goyal <vgoyal@redhat.com> | 2010-10-01 21:16:42 +0200 |
|---|---|---|
| committer | Jens Axboe <jaxboe@fusionio.com> | 2010-10-01 21:16:42 +0200 |
| commit | c49c06e4960949a9bced708858433fcf6ca36a9c (patch) | |
| tree | 071c65544a98b6b0b599896591855f8ac69ab79a /block | |
| parent | 9355aede5a3c4975e0ba8bbfe2b9d1fd73308916 (diff) | |
| download | op-kernel-dev-c49c06e4960949a9bced708858433fcf6ca36a9c.zip op-kernel-dev-c49c06e4960949a9bced708858433fcf6ca36a9c.tar.gz | |
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>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-throttle.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index c1bc1b6..56ad453 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -430,6 +430,7 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, bool rw = bio_data_dir(bio); unsigned int io_allowed; unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; + u64 tmp; jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; @@ -439,7 +440,20 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); - io_allowed = (tg->iops[rw] * jiffy_elapsed_rnd) / HZ; + /* + * jiffy_elapsed_rnd should not be a big value as minimum iops can be + * 1 then at max jiffy elapsed should be equivalent of 1 second as we + * will allow dispatch after 1 second and after that slice should + * have been trimmed. + */ + + tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; + do_div(tmp, HZ); + + if (tmp > UINT_MAX) + io_allowed = UINT_MAX; + else + io_allowed = tmp; if (tg->io_disp[rw] + 1 <= io_allowed) { if (wait) |
