| Message ID | YmjODd4aif9BzFuO@slm.duckdns.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [block-5.18] iocost: don't reset the inuse weight of under-weighted debtors | expand |
On Tue, 26 Apr 2022 19:01:01 -1000, Tejun Heo wrote: > When an iocg is in debt, its inuse weight is owned by debt handling and > should stay at 1. This invariant was broken when determining the amount of > surpluses at the beginning of donation calculation - when an iocg's > hierarchical weight is too low, the iocg is excluded from donation > calculation and its inuse is reset to its active regardless of its > indebtedness, triggering warnings like the following: > > [...] Applied, thanks! [1/1] iocost: don't reset the inuse weight of under-weighted debtors commit: 8c936f9ea11ec4e35e288810a7503b5c841a355f Best regards,
diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 70a0a3d680a35..9bd670999d0af 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -2322,7 +2322,17 @@ static void ioc_timer_fn(struct timer_list *timer) iocg->hweight_donating = hwa; iocg->hweight_after_donation = new_hwi; list_add(&iocg->surplus_list, &surpluses); - } else { + } else if (!iocg->abs_vdebt) { + /* + * @iocg doesn't have enough to donate. Reset + * its inuse to active. + * + * Don't reset debtors as their inuse's are + * owned by debt handling. This shouldn't affect + * donation calculuation in any meaningful way + * as @iocg doesn't have a meaningful amount of + * share anyway. + */ TRACE_IOCG_PATH(inuse_shortage, iocg, &now, iocg->inuse, iocg->active, iocg->hweight_inuse, new_hwi);
When an iocg is in debt, its inuse weight is owned by debt handling and should stay at 1. This invariant was broken when determining the amount of surpluses at the beginning of donation calculation - when an iocg's hierarchical weight is too low, the iocg is excluded from donation calculation and its inuse is reset to its active regardless of its indebtedness, triggering warnings like the following: WARNING: CPU: 5 PID: 0 at block/blk-iocost.c:1416 iocg_kick_waitq+0x392/0x3a0 ... RIP: 0010:iocg_kick_waitq+0x392/0x3a0 Code: 00 00 be ff ff ff ff 48 89 4d a8 e8 98 b2 70 00 48 8b 4d a8 85 c0 0f 85 4a fe ff ff 0f 0b e9 43 fe ff ff 0f 0b e9 4d fe ff ff <0f> 0b e9 50 fe ff ff e8 a2 ae 70 00 66 90 0f 1f 44 00 00 55 48 89 RSP: 0018:ffffc90000200d08 EFLAGS: 00010016 ... <IRQ> ioc_timer_fn+0x2e0/0x1470 call_timer_fn+0xa1/0x2c0 ... As this happens only when an iocg's hierarchical weight is negligible, its impact likely is limited to triggering the warnings. Fix it by skipping resetting inuse of under-weighted debtors. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Rik van Riel <riel@surriel.com> Fixes: c421a3eb2e27 ("blk-iocost: revamp debt handling") Cc: stable@vger.kernel.org # v5.10+ --- block/blk-iocost.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)