[RFC PATCH 5/5] cachefiles: add restore command to recover inflight ondemand read requests

[JeffleXu]

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 at linux.alibaba.com>
> Signed-off-by: Jia Zhu <zhujia.zj at bytedance.com>
> Signed-off-by: Xin Yin <yinxin.x at bytedance.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.


> +	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;

-- 
Thanks,
Jingbo