Hi,
在 2022/11/15 6:07, Tejun Heo 写道:
On Fri, Nov 04, 2022 at 10:39:37AM +0800, Yu Kuai wrote:
From: Yu Kuai <yukuai3@xxxxxxxxxx>
match_u64() is called inside ioc->lock, which causes smatch static
checker warnings:
block/blk-iocost.c:3211 ioc_qos_write() warn: sleeping in atomic context
block/blk-iocost.c:3240 ioc_qos_write() warn: sleeping in atomic context
block/blk-iocost.c:3407 ioc_cost_model_write() warn: sleeping in atomic
context
Fix the problem by introducing a mutex and using it while prasing input
params.
It bothers me that parsing an u64 string requires a GFP_KERNEL memory
allocation.
@@ -2801,9 +2806,11 @@ static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos)
{
struct ioc *ioc = rqos_to_ioc(rqos);
+ mutex_lock(&ioc->params_mutex);
spin_lock_irq(&ioc->lock);
ioc_refresh_params(ioc, false);
spin_unlock_irq(&ioc->lock);
+ mutex_unlock(&ioc->params_mutex);
}
Aren't the params still protected by ioc->lock? Why do we need to grab both?
Yes, the params is updated inside ioc->lock, but they can be read
without the lock before updating them, which is protected by mutex
instead.
Any chance I can persuade you into updating match_NUMBER() helpers to not
use match_strdup()? They can easily disable irq/preemption and use percpu
buffers and we won't need most of this patchset.
Do you mean preallocated percpu buffer? Is there any example I can
learn? Anyway, replace match_strdup() to avoid memory allocation sounds
good.
Thanks,
Kuai
Thanks.
