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

From: Gang He <ghe@suse.com>
To: Joseph Qi <joseph.qi@linux.alibaba.com>,
	mark@fasheh.com, jlbec@evilplan.org
Cc: linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com,
	akpm@linux-foundation.org
Subject: Re: [PATCH] ocfs2: avoid getting dlm lock of the target directory multiple times during reflink process
Date: Tue, 7 Sep 2021 17:40:26 +0800	[thread overview]
Message-ID: <7510251b-0bf5-f14d-6c44-30385152a883@suse.com> (raw)
In-Reply-To: <41bc413d-0926-0eae-6772-076314bbae53@linux.alibaba.com>

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
> 
> 