linux-kernel - Re: [PATCH 12/12] cachefiles: make on-demand read killable

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Date: Thu, 25 Apr 2024 13:15:37 +0800
From: Jia Zhu <zhujia.zj@...edance.com>
To: libaokun@...weicloud.com, netfs@...ts.linux.dev
Cc: dhowells@...hat.com, jlayton@...nel.org, jefflexu@...ux.alibaba.com,
 linux-erofs@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, Baokun Li <libaokun1@...wei.com>,
 Hou Tao <houtao1@...wei.com>, zhujia.zj@...edance.com
Subject: Re: [PATCH 12/12] cachefiles: make on-demand read killable



在 2024/4/24 11:39, libaokun@...weicloud.com 写道:
> From: Baokun Li <libaokun1@...wei.com>
> 
> Replacing wait_for_completion() with wait_for_completion_killable() in
> cachefiles_ondemand_send_req() allows us to kill processes that might
> trigger a hunk_task if the daemon is abnormal.
> 
> But now only CACHEFILES_OP_READ is killable, because OP_CLOSE and OP_OPEN
> is initiated from kworker context and the signal is prohibited in these
> kworker.
> 
> Note that when the req in xas changes, i.e. xas_load(&xas) != req, it
> means that a process will complete the current request soon, so wait
> again for the request to be completed.
> 
> Suggested-by: Hou Tao <houtao1@...wei.com>
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

Reviewed-by: Jia Zhu <zhujia.zj@...edance.com>

> ---
>   fs/cachefiles/ondemand.c | 21 +++++++++++++++++++--
>   1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
> index 673e7ad52041..b766430f4abf 100644
> --- a/fs/cachefiles/ondemand.c
> +++ b/fs/cachefiles/ondemand.c
> @@ -525,8 +525,25 @@ static int cachefiles_ondemand_send_req(struct cachefiles_object *object,
>   		goto out;
>   
>   	wake_up_all(&cache->daemon_pollwq);
> -	wait_for_completion(&req->done);
> -	ret = req->error;
> +wait:
> +	ret = wait_for_completion_killable(&req->done);
> +	if (!ret) {
> +		ret = req->error;
> +	} else {
> +		xas_reset(&xas);
> +		xas_lock(&xas);
> +		if (xas_load(&xas) == req) {
> +			xas_store(&xas, NULL);
> +			ret = -EINTR;
> +		}
> +		xas_unlock(&xas);
> +
> +		/* Someone will complete it soon. */
> +		if (ret != -EINTR) {
> +			cpu_relax();
> +			goto wait;
> +		}
> +	}
>   	cachefiles_req_put(req);
>   	return ret;
>   out: