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Sender: Tejun Heo <htejun@gmail.com>
Date:   Mon, 31 Oct 2022 12:30:58 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Ian Kent <raven@themaw.net>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Minchan Kim <minchan@kernel.org>,
        Eric Sandeen <sandeen@sandeen.net>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Rick Lindsley <ricklind@linux.vnet.ibm.com>,
        David Howells <dhowells@redhat.com>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Carlos Maiolino <cmaiolino@redhat.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] kernfs: dont take i_lock on inode attr read
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References: <166606025456.13363.3829702374064563472.stgit@donald.themaw.net>
 <166606036215.13363.1288735296954908554.stgit@donald.themaw.net>
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On Tue, Oct 18, 2022 at 10:32:42AM +0800, Ian Kent wrote:
> The kernfs write lock is held when the kernfs node inode attributes
> are updated. Therefore, when either kernfs_iop_getattr() or
> kernfs_iop_permission() are called the kernfs node inode attributes
> won't change.
> 
> Consequently concurrent kernfs_refresh_inode() calls always copy the
> same values from the kernfs node.
> 
> So there's no need to take the inode i_lock to get consistent values
> for generic_fillattr() and generic_permission(), the kernfs read lock
> is sufficient.
> 
> Signed-off-by: Ian Kent <raven@themaw.net>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun