linux-kernel - Re: [PATCH 01/12] cachefiles: remove request from xarry during flush requests

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Message-ID: <6e4a20f7-263a-46be-81cc-2667353c452d@linux.alibaba.com>
Date: Mon, 6 May 2024 11:48:54 +0800
From: Jingbo Xu <jefflexu@...ux.alibaba.com>
To: libaokun@...weicloud.com, netfs@...ts.linux.dev
Cc: dhowells@...hat.com, jlayton@...nel.org, zhujia.zj@...edance.com,
 linux-erofs@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH 01/12] cachefiles: remove request from xarry during flush
 requests



On 4/24/24 11:39 AM, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> This prevents concurrency from causing access to a freed req.

Could you give more details on how the concurrent access will happen?
How could another process access the &cache->reqs xarray after it has
been flushed?

> ---
>  fs/cachefiles/daemon.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
> index 6465e2574230..ccb7b707ea4b 100644
> --- a/fs/cachefiles/daemon.c
> +++ b/fs/cachefiles/daemon.c
> @@ -159,6 +159,7 @@ static void cachefiles_flush_reqs(struct cachefiles_cache *cache)
>  	xa_for_each(xa, index, req) {
>  		req->error = -EIO;
>  		complete(&req->done);
> +		__xa_erase(xa, index);
>  	}
>  	xa_unlock(xa);
>  

-- 
Thanks,
Jingbo