on 9/16/2023 7:06 PM, Bernd Schubert wrote:
>
>
> On 9/14/23 17:45, Kemeng Shi wrote:
>> Commit 670d21c6e17f6 ("fuse: remove reliance on bdi congestion") change how
>> congestion_threshold is used and lock in
>> fuse_conn_congestion_threshold_write is not needed anymore.
>> 1. Access to supe_block is removed along with removing of bdi congestion.
>> Then down_read(&fc->killsb) which protecting access to super_block is no
>> needed.
>> 2. Compare num_background and congestion_threshold without holding
>> bg_lock. Then there is no need to hold bg_lock to update
>> congestion_threshold.
>>
>> Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
>> ---
>> fs/fuse/control.c | 4 ----
>> 1 file changed, 4 deletions(-)
>>
>> diff --git a/fs/fuse/control.c b/fs/fuse/control.c
>> index 247ef4f76761..c5d7bf80efed 100644
>> --- a/fs/fuse/control.c
>> +++ b/fs/fuse/control.c
>> @@ -174,11 +174,7 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
>> if (!fc)
>> goto out;
>> - down_read(&fc->killsb);
>> - spin_lock(&fc->bg_lock);
>> fc->congestion_threshold = val;
>> - spin_unlock(&fc->bg_lock);
>> - up_read(&fc->killsb);
>> fuse_conn_put(fc);
>> out:
>> return ret;
>
> Yeah, I don't see readers holding any of these locks.
> I just wonder if it wouldn't be better to use WRITE_ONCE to ensure a single atomic operation to store the value.
Sure, WRITE_ONCE looks better. I wonder if we should use READ_ONCE from reader.
Would like to get any advice. Thanks!
>
>
> Thanks,
> Bernd
>
