linux-kernel - Re: [PATCH] sysfs: kill an extra put in sysfs_create

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Date:	Thu, 19 Jul 2007 01:41:30 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Tejun Heo <htejun@...il.com>
CC:	Satyam Sharma <satyam.sharma@...il.com>,
	Gabriel C <nix.or.die@...glemail.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Lameter <clameter@....com>, gregkh@...e.de,
	miles.lane@...il.com
Subject: Re: [PATCH] sysfs: kill an extra put in sysfs_create_link() failure
 path

Tejun Heo wrote:
> Satyam Sharma wrote:
>>>> sysfs_find_dirent() -- to check for -EEXIST -- should be called
>>>> *before* we create the new dentry for the to-be-created symlink
>>>> in the first place. [ It's weird to grab a reference on the target
>>>> for ourselves (and in fact even allocate the new dirent for the
>>>> to-be-created symlink) and /then/ check for erroneous usage,
>>>> and then go about undoing all that we should never have done
>>>> at all. ] So this test could, and should, be made earlier, IMHO.
>>> Locking.
>> Well s/sysfs_find_dirent/sysfs_get_dirent/ then. And then simply put
>> down the reference later.
> 
> Isn't that the current code?

Oops, somehow thought you were talking about allocating it first.
Gee... what difference does using sysfs_get_dirent() make?  Do you think
the following code is correct?

	sd = sysfs_get_dirent("some name");
	if (sd != NULL)
		return -EEXIST;
	lock;
	add_new_node("some name");
	unlock;
	sysfs_put_dirent(sd);

-- 
tejun
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