Re: [RFC PATCH 2/2] watch_queue: Fix pipe accounting

[Eric Sandeen <sandeen@sandeen.net>]

On 2/14/25 10:49 AM, David Howells wrote:
> Eric Sandeen <sandeen@redhat.com> wrote:
> 
>> -	if (!pipe_has_watch_queue(pipe)) {
>> -		pipe->max_usage = nr_slots;
>> -		pipe->nr_accounted = nr_slots;
>> -	}
>> +	pipe->max_usage = nr_slots;
>> +	pipe->nr_accounted = nr_slots;
> 
> Hmmm...   The pipe ring is supposed to have some spare capacity when used as a
> watch queue so that you can bung at least a few messages into it.

If the pipe has an original number of buffers on it, and
then watch_queue_set_size adjusts that number - where does
the spare capacity come from? Who adds it / where?

Thanks,
-Eric

> David
> 
>