linux-kernel - Re: [PATCH] devtmpfs: Calling delete

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Message-ID: <20131209090530.GA4586@kroah.com>
Date:	Mon, 9 Dec 2013 01:05:30 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Axel Lin <axel.lin@...ics.com>
Cc:	Rob Landley <rob@...dley.net>, Al Viro <viro@...iv.linux.org.uk>,
	Kay Sievers <kay.sievers@...y.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] devtmpfs: Calling delete_path() only when necessary

On Mon, Dec 09, 2013 at 04:54:29PM +0800, Axel Lin wrote:
> 2013/12/9 Greg Kroah-Hartman <gregkh@...uxfoundation.org>:
> > On Wed, Dec 04, 2013 at 02:44:14PM +0800, Axel Lin wrote:
> >> 2013/12/4 Rob Landley <rob@...dley.net>:
> >> > On 11/16/2013 02:15:23 AM, Axel Lin wrote:
> >> >>
> >> >> The deleted variable is always 1 in current code.
> >> >> Initialize deleted variable to be 0, so delete_path() will be called only
> >> >> when
> >> >> necessary.
> >> >>
> >> >> Signed-off-by: Axel Lin <axel.lin@...ics.com>
> >> >
> >> >
> >> > I'm not seeing this in linux-next, or a reply on the web archive. Assuming
> >> > nobody's objected to this, you might want to forward it to
> >> > trivial@...nel.org.
> >> >
> >> > That said, you could describe what it _does_ a little more?
> >>
> >> I was expecting Greg to pick up this patch.
> >>
> >> I thought the description is pretty clear.
> >> What the patch does is changing the init value of deleted variable to 0.
> >> The intention of this change is to avoid unnecessary delete_path() call.
> >
> > I agree the logic is a bit odd here, but are you seeing an "unnecessary"
> > delete_path() call happening?  The code has always been like this from
> > what I can tell...
> 
> Honestly, I havn't see the "unnecessary" delete_path() call happening druing my
> test. I look at the code when I was debugging a hangup issue.
> (In the end, I think the issue is not related to the devtmpfs code.)
> But I found the logic for the deleted variable looks odd.
> There are below possible (unlikely) case:
> When strchr(nodename, '/') != 0 and
> 1. If dentry->d_inode is NULL
> 2. vfs_getattr returns error
> 3. vfs_unlink returns error except -ENOENT.
> 
> In these cases, delete_path() will fail anyway.
> 
> Although this is a unlikely case, and I know the code is there since initial
> commit. But I think it's still good to fix it.

Have you tested your patch to verify nothing breaks?
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