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

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Message-ID: <CAFRkauCQdOyWbck+WtmNxtnenKyPAFNcqqUgcGSb1kAqj56sYA@mail.gmail.com>
Date:	Mon, 9 Dec 2013 16:54:29 +0800
From:	Axel Lin <axel.lin@...ics.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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

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.

Regards,
Axel
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