linux-kernel - Re: [External] Re: [PATCH 3/5] cachefiles: resend an open request if the read request's object is closed

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Message-ID: <3051133b-1408-2ccb-b22f-e5ee990bdc4f@linux.alibaba.com>
Date:   Thu, 13 Oct 2022 09:47:11 +0800
From:   JeffleXu <jefflexu@...ux.alibaba.com>
To:     Jia Zhu <zhujia.zj@...edance.com>, dhowells@...hat.com,
        xiang@...nel.org
Cc:     linux-cachefs@...hat.com, linux-erofs@...ts.ozlabs.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        yinxin.x@...edance.com
Subject: Re: [External] Re: [PATCH 3/5] cachefiles: resend an open request if
 the read request's object is closed



On 10/12/22 11:37 PM, Jia Zhu wrote:
> 
> 
> 在 2022/10/12 15:53, JeffleXu 写道:
>>
>>
>> On 10/11/22 9:15 PM, Jia Zhu wrote:
>>> @@ -254,12 +282,18 @@ ssize_t cachefiles_ondemand_daemon_read(struct
>>> cachefiles_cache *cache,
>>>        * request distribution fair.
>>>        */
>>>       xa_lock(&cache->reqs);
>>> -    req = xas_find_marked(&xas, UINT_MAX, CACHEFILES_REQ_NEW);
>>> -    if (!req && cache->req_id_next > 0) {
>>> -        xas_set(&xas, 0);
>>> -        req = xas_find_marked(&xas, cache->req_id_next - 1,
>>> CACHEFILES_REQ_NEW);
>>> +retry:
>>> +    xas_for_each_marked(&xas, req, xa_max, CACHEFILES_REQ_NEW) {
>>> +        if (cachefiles_ondemand_skip_req(req))
>>> +            continue;
>>> +        break;
>>>       }
>>>       if (!req) {
>>> +        if (cache->req_id_next > 0 && xa_max == ULONG_MAX) {
>>> +            xas_set(&xas, 0);
>>> +            xa_max = cache->req_id_next - 1;
>>> +            goto retry;
>>> +        }
>>
>> I would suggest abstracting the "xas_for_each_marked(...,
>> CACHEFILES_REQ_NEW)" part into a helper function to avoid the "goto
>> retry".
>>
> Hi JingBo,
> 
> Thanks for your advice. Are the following revises appropriate？
> 
> static struct cachefiles_req *cachefiles_ondemand_select_req(struct
> xa_state *xas, unsigned long xa_max)
> {
>     struct cachefiles_req *req;
>     struct cachefiles_ondemand_info *info;
> 
>     xas_for_each_marked(xas, req, xa_max, CACHEFILES_REQ_NEW) {
>         if (!req || req->msg.opcode != CACHEFILES_OP_READ)

xas_for_each_marked() will guarantee that @req won't be NULL, and thus
the NULL check here in unnecessary. Otherwise LGTM.

>             return req;
>         info = req->object->private;
>         if (info->state == CACHEFILES_ONDEMAND_OBJSTATE_close) {
>             cachefiles_ondemand_set_object_reopening(req->object);
>             queue_work(fscache_wq, &info->work);
>             continue;
>         } else if (info->state == CACHEFILES_ONDEMAND_OBJSTATE_reopening) {
>             continue;
>         }
>         return req;
>     }
>     return NULL;
> }
> 
> ...
> 
>  xa_lock(&cache->reqs);
>     req = cachefiles_ondemand_select_req(&xas, ULONG_MAX);
>     if (!req && cache->req_id_next > 0) {
>         xas_set(&xas, 0);
>         req = cachefiles_ondemand_select_req(&xas, cache->req_id_next - 1);
>     }
>     if (!req) {
>         xa_unlock(&cache->reqs);
>         return 0;
>     }
>>


-- 
Thanks,
Jingbo