linux-kernel - Re: [External] Re: [RFC PATCH 5/5] cachefiles: add restore command to recover inflight ondemand read requests

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Message-ID: <bdbf258d-096c-4c44-c195-0ecff7504a32@bytedance.com>
Date:   Sun, 9 Oct 2022 17:52:32 +0800
From:   Jia Zhu <zhujia.zj@...edance.com>
To:     JeffleXu <jefflexu@...ux.alibaba.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, Gao Xiang <hsiangkao@...ux.alibaba.com>
Subject: Re: [External] Re: [RFC PATCH 5/5] cachefiles: add restore command to
 recover inflight ondemand read requests



在 2022/10/8 17:00, JeffleXu 写道:
> 
> 
> On 8/18/22 9:52 PM, Jia Zhu wrote:
>> Previously, in ondemand read scenario, if the anonymous fd was closed by
>> user daemon, inflight and subsequent read requests would return EIO.
>> As long as the device connection is not released, user daemon can hold
>> and restore inflight requests by setting the request flag to
>> CACHEFILES_REQ_NEW.
>>
>> Suggested-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
>> Signed-off-by: Jia Zhu <zhujia.zj@...edance.com>
>> Signed-off-by: Xin Yin <yinxin.x@...edance.com>
>> ---
>>   fs/cachefiles/daemon.c   |  1 +
>>   fs/cachefiles/internal.h |  3 +++
>>   fs/cachefiles/ondemand.c | 23 +++++++++++++++++++++++
>>   3 files changed, 27 insertions(+)
>>
>> diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
>> index c74bd1f4ecf5..014369266cb2 100644
>> --- a/fs/cachefiles/daemon.c
>> +++ b/fs/cachefiles/daemon.c
>> @@ -77,6 +77,7 @@ static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
>>   	{ "tag",	cachefiles_daemon_tag		},
>>   #ifdef CONFIG_CACHEFILES_ONDEMAND
>>   	{ "copen",	cachefiles_ondemand_copen	},
>> +	{ "restore",	cachefiles_ondemand_restore	},
>>   #endif
>>   	{ "",		NULL				}
>>   };
>> diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
>> index b4af67f1cbd6..d504c61a5f03 100644
>> --- a/fs/cachefiles/internal.h
>> +++ b/fs/cachefiles/internal.h
>> @@ -303,6 +303,9 @@ extern ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache,
>>   extern int cachefiles_ondemand_copen(struct cachefiles_cache *cache,
>>   				     char *args);
>>   
>> +extern int cachefiles_ondemand_restore(struct cachefiles_cache *cache,
>> +					char *args);
>> +
>>   extern int cachefiles_ondemand_init_object(struct cachefiles_object *object);
>>   extern void cachefiles_ondemand_clean_object(struct cachefiles_object *object);
>>   
>> diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
>> index 79ffb19380cd..5b1c447da976 100644
>> --- a/fs/cachefiles/ondemand.c
>> +++ b/fs/cachefiles/ondemand.c
>> @@ -178,6 +178,29 @@ int cachefiles_ondemand_copen(struct cachefiles_cache *cache, char *args)
>>   	return ret;
>>   }
>>   
>> +int cachefiles_ondemand_restore(struct cachefiles_cache *cache, char *args)
>> +{
>> +	struct cachefiles_req *req;
>> +
>> +	XA_STATE(xas, &cache->reqs, 0);
>> +
>> +	if (!test_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags))
>> +		return -EOPNOTSUPP;
>> +
>> +	/*
>> +	 * Search the requests which being processed before
>> +	 * the user daemon crashed.
>> +	 * Set the CACHEFILES_REQ_NEW flag and user daemon will reprocess it.
>> +	 */
> 
> The comment can be improved as:
> 
> 	Reset the requests to CACHEFILES_REQ_NEW state, so that the
>          requests have been processed halfway before the crash of the
>          user daemon could be reprocessed after the recovery.
> 
Thanks, I'll apply it.
> 
>> +	xas_lock(&xas);
>> +	xas_for_each(&xas, req, ULONG_MAX)
>> +		xas_set_mark(&xas, CACHEFILES_REQ_NEW);
>> +	xas_unlock(&xas);
>> +
>> +	wake_up_all(&cache->daemon_pollwq);
>> +	return 0;
>> +}
>> +
>>   static int cachefiles_ondemand_get_fd(struct cachefiles_req *req)
>>   {
>>   	struct cachefiles_object *object;
>