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author | Kemeng Shi <shikemeng@huawei.com> | 2022-12-05 19:57:04 +0800 |
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committer | Jens Axboe <axboe@kernel.dk> | 2022-12-05 13:44:42 -0700 |
commit | 183daeb11de871b073515d14ec1e3bc0da79e038 (patch) | |
tree | 1cc9b4295e6d38c26aac493e8efa4956d2a569d8 | |
parent | eb184791821409c37fef4f67638bb56bdaa82900 (diff) | |
download | linux-183daeb11de871b073515d14ec1e3bc0da79e038.tar.gz linux-183daeb11de871b073515d14ec1e3bc0da79e038.tar.bz2 linux-183daeb11de871b073515d14ec1e3bc0da79e038.zip |
blk-throttle: correct calculation of wait time in tg_may_dispatch
In C language, When executing "if (expression1 && expression2)" and
expression1 return false, the expression2 may not be executed.
For "tg_within_bps_limit(tg, bio, bps_limit, &bps_wait) &&
tg_within_iops_limit(tg, bio, iops_limit, &iops_wait))", if bps is
limited, tg_within_bps_limit will return false and
tg_within_iops_limit will not be called. So even bps and iops are
both limited, iops_wait will not be calculated and is always zero.
So wait time of iops is always ignored.
Fix this by always calling tg_within_bps_limit and tg_within_iops_limit
to get wait time for both bps and iops.
Observed that:
1. Wait time in tg_within_iops_limit/tg_within_bps_limit need always
be stored as wait argument is always passed.
2. wait time is stored to zero if iops/bps is limited otherwise non-zero
is stored.
Simpfy tg_within_iops_limit/tg_within_bps_limit by removing wait argument
and return wait time directly. Caller tg_may_dispatch checks if wait time
is zero to find if iops/bps is limited.
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
Link: https://lore.kernel.org/r/20221205115709.251489-5-shikemeng@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r-- | block/blk-throttle.c | 38 |
1 files changed, 13 insertions, 25 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 75010110d481..d5b7a2354ad7 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -822,17 +822,15 @@ static void tg_update_carryover(struct throtl_grp *tg) tg->carryover_ios[READ], tg->carryover_ios[WRITE]); } -static bool tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio, - u32 iops_limit, unsigned long *wait) +static unsigned long tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio, + u32 iops_limit) { bool rw = bio_data_dir(bio); unsigned int io_allowed; unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; if (iops_limit == UINT_MAX) { - if (wait) - *wait = 0; - return true; + return 0; } jiffy_elapsed = jiffies - tg->slice_start[rw]; @@ -842,21 +840,16 @@ static bool tg_within_iops_limit(struct throtl_grp *tg, struct bio *bio, io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) + tg->carryover_ios[rw]; if (tg->io_disp[rw] + 1 <= io_allowed) { - if (wait) - *wait = 0; - return true; + return 0; } /* Calc approx time to dispatch */ jiffy_wait = jiffy_elapsed_rnd - jiffy_elapsed; - - if (wait) - *wait = jiffy_wait; - return false; + return jiffy_wait; } -static bool tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio, - u64 bps_limit, unsigned long *wait) +static unsigned long tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio, + u64 bps_limit) { bool rw = bio_data_dir(bio); u64 bytes_allowed, extra_bytes; @@ -865,9 +858,7 @@ static bool tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio, /* no need to throttle if this bio's bytes have been accounted */ if (bps_limit == U64_MAX || bio_flagged(bio, BIO_BPS_THROTTLED)) { - if (wait) - *wait = 0; - return true; + return 0; } jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; @@ -880,9 +871,7 @@ static bool tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio, bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) + tg->carryover_bytes[rw]; if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) { - if (wait) - *wait = 0; - return true; + return 0; } /* Calc approx time to dispatch */ @@ -897,9 +886,7 @@ static bool tg_within_bps_limit(struct throtl_grp *tg, struct bio *bio, * up we did. Add that time also. */ jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); - if (wait) - *wait = jiffy_wait; - return false; + return jiffy_wait; } /* @@ -947,8 +934,9 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio, jiffies + tg->td->throtl_slice); } - if (tg_within_bps_limit(tg, bio, bps_limit, &bps_wait) && - tg_within_iops_limit(tg, bio, iops_limit, &iops_wait)) { + bps_wait = tg_within_bps_limit(tg, bio, bps_limit); + iops_wait = tg_within_iops_limit(tg, bio, iops_limit); + if (bps_wait + iops_wait == 0) { if (wait) *wait = 0; return true; |