linux-kernel - Re: [PATCH 5.10 1/5] kernfs: add a revision to identify directory node changes

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Message-ID: <2025052147-sushi-panther-ab51@gregkh>
Date: Wed, 21 May 2025 06:16:01 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Qingfang Deng <dqfext@...il.com>
Cc: stable@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org, Ian Kent <raven@...maw.net>,
	Miklos Szeredi <mszeredi@...hat.com>
Subject: Re: [PATCH 5.10 1/5] kernfs: add a revision to identify directory
 node changes

On Wed, May 21, 2025 at 09:53:31AM +0800, Qingfang Deng wrote:
> From: Ian Kent <raven@...maw.net>
> 
> Commit 895adbec302e92086359e6fd92611ac3be6d92c3 upstream.
> 
> Add a revision counter to kernfs directory nodes so it can be used
> to detect if a directory node has changed during negative dentry
> revalidation.
> 
> There's an assumption that sizeof(unsigned long) <= sizeof(pointer)
> on all architectures and as far as I know that assumption holds.
> 
> So adding a revision counter to the struct kernfs_elem_dir variant of
> the kernfs_node type union won't increase the size of the kernfs_node
> struct. This is because struct kernfs_elem_dir is at least
> sizeof(pointer) smaller than the largest union variant. It's tempting
> to make the revision counter a u64 but that would increase the size of
> kernfs_node on archs where sizeof(pointer) is smaller than the revision
> counter.
> 
> Reviewed-by: Miklos Szeredi <mszeredi@...hat.com>
> Signed-off-by: Ian Kent <raven@...maw.net>
> Link: https://lore.kernel.org/r/162642769895.63632.8356662784964509867.stgit@web.messagingengine.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

When forwarding on patches, you HAVE to sign off on them as well.

thanks,

greg k-h