linux-kernel - Re: [External] Re: [PATCH V4 4/5] cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode

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Message-ID: <2a39ced1-05f1-d696-1905-4ff5199fa41b@bytedance.com>
Date:   Wed, 29 Mar 2023 16:08:49 +0800
From:   Jia Zhu <zhujia.zj@...edance.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-cachefs@...hat.com, linux-erofs@...ts.ozlabs.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xin Yin <yinxin.x@...edance.com>,
        Jingbo Xu <jefflexu@...ux.alibaba.com>, zhujia.zj@...edance.com
Subject: Re: [External] Re: [PATCH V4 4/5] cachefiles: narrow the scope of
 triggering EPOLLIN events in ondemand mode



在 2023/3/28 22:19, David Howells 写道:
> Jia Zhu <zhujia.zj@...edance.com> wrote:
> 
>> +		if (!xa_empty(xa)) {
>> +			xa_lock(xa);
>> +			xa_for_each_marked(xa, index, req, CACHEFILES_REQ_NEW) {
>> +				if (!cachefiles_ondemand_is_reopening_read(req)) {
>> +					mask |= EPOLLIN;
>> +					break;
>> +				}
>> +			}
>> +			xa_unlock(xa);
>> +		}
> 
> I wonder if there's a more efficient way to do this.  I guess it depends on
> how many reqs you expect to get in a queue.  It might be worth taking the
> rcu_read_lock before calling xa_lock() and holding it over the whole loop.
> 
Thanks for the advice, will use rcu_read_lock（unlock） to replace it.
> David
>