linux-kernel - Re: [PATCH] ocfs2: avoid getting dlm lock of the target directory multiple times during reflink process

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Message-ID: <7510251b-0bf5-f14d-6c44-30385152a883@suse.com>
Date:   Tue, 7 Sep 2021 17:40:26 +0800
From:   Gang He <ghe@...e.com>
To:     Joseph Qi <joseph.qi@...ux.alibaba.com>, mark@...heh.com,
        jlbec@...lplan.org
Cc:     linux-kernel@...r.kernel.org, ocfs2-devel@....oracle.com,
        akpm@...ux-foundation.org
Subject: Re: [PATCH] ocfs2: avoid getting dlm lock of the target directory
 multiple times during reflink process

Hi Joseph,

On 2021/9/6 19:14, Joseph Qi wrote:
> Hi Gang,
> 
> 
> On 8/26/21 3:59 PM, Gang He wrote:
>> During the reflink process, we should acquire the target directory
>> inode dlm lock at the beginning, and hold this dlm lock until end
>> of the function.
>> With this patch, we avoid dlm lock ping-pong effect when clone
>> files to the same directory simultaneously from multiple nodes.
>> There is a typical user scenario, users regularly back up files
>> to a specified directory through the reflink feature from the
>> multiple nodes.
>>
> Since now it take dir inode lock across the whole reflink, it may impact
> other concurrent operations under the same directory.
> Have you evaluated such cases?
So far, I do not find there is any risk for taking dir inode lock across 
the reflink function, it will block getting that dir inode lock a little 
time, but avoid ping-pong effect during the reflink function.


Thanks
Gang


> 
> Thanks,
> Joseph
> 
>