Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <3f75d266-7ccd-be6d-657c-fe0633b25687@linux.alibaba.com>
Date:   Fri, 9 Sep 2022 17:55:41 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0)
 Gecko/20100101 Thunderbird/91.13.0
Subject: Re: [PATCH V2 4/5] erofs: remove duplicated unregister_cookie
Content-Language: en-US
To:     Jia Zhu <zhujia.zj@bytedance.com>, linux-erofs@lists.ozlabs.org,
        xiang@kernel.org, chao@kernel.org
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        yinxin.x@bytedance.com, huyue2@coolpad.com
References: <20220902105305.79687-1-zhujia.zj@bytedance.com>
 <20220902105305.79687-5-zhujia.zj@bytedance.com>
From:   JeffleXu <jefflexu@linux.alibaba.com>
In-Reply-To: <20220902105305.79687-5-zhujia.zj@bytedance.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 9/2/22 6:53 PM, Jia Zhu wrote:
> In erofs umount scenario, erofs_fscache_unregister_cookie() is called
> twice in kill_sb() and put_super().
> 
> It works for original semantics, cause 'ctx' will be set to NULL in
> put_super() and will not be unregister again in kill_sb().
> However, in shared domain scenario, we use refcount to maintain the
> lifecycle of cookie. Unregister the cookie twice will cause it to be
> released early.
> 
> For the above reasons, this patch removes duplicate unregister_cookie
> and move fscache_unregister_* before shotdown_super() to prevent busy
> inode(ctx->inode) when umount.
> 
> Signed-off-by: Jia Zhu <zhujia.zj@bytedance.com>
> ---
>  fs/erofs/super.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 69de1731f454..667a78f0ee70 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -919,19 +919,20 @@ static void erofs_kill_sb(struct super_block *sb)
>  		kill_litter_super(sb);
>  		return;
>  	}
> -	if (erofs_is_fscache_mode(sb))
> -		generic_shutdown_super(sb);
> -	else
> -		kill_block_super(sb);
> -
>  	sbi = EROFS_SB(sb);
>  	if (!sbi)
>  		return;
>  
> +	if (erofs_is_fscache_mode(sb)) {
> +		erofs_fscache_unregister_cookie(&sbi->s_fscache);
> +		erofs_fscache_unregister_fs(sb);
> +		generic_shutdown_super(sb);

Generally we can't do clean ups before generic_shutdown_super(), since
generic_shutdown_super() may trigger IO, e.g. in sync_filesystem(),
though it's not the case for erofs (read-only).

How about embedding erofs_fscache_unregister_cookie() into
erofs_fscache_unregister_fs(), and thus we can check domain_id in
erofs_fscache_unregister_fs()?

> +	} else {
> +		kill_block_super(sb);
> +	}
> +
>  	erofs_free_dev_context(sbi->devs);
>  	fs_put_dax(sbi->dax_dev, NULL);
> -	erofs_fscache_unregister_cookie(&sbi->s_fscache);
> -	erofs_fscache_unregister_fs(sb);
>  	kfree(sbi->opt.fsid);
>  	kfree(sbi->opt.domain_id);
>  	kfree(sbi);
> @@ -951,7 +952,6 @@ static void erofs_put_super(struct super_block *sb)
>  	iput(sbi->managed_cache);
>  	sbi->managed_cache = NULL;
>  #endif
> -	erofs_fscache_unregister_cookie(&sbi->s_fscache);
>  }
>  
>  struct file_system_type erofs_fs_type = {

-- 
Thanks,
Jingbo