linux-kernel - Re: [PATCH] vfs: use kstrdup()

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Message-ID: <20080721052713.GY28946@ZenIV.linux.org.uk>
Date:	Mon, 21 Jul 2008 06:27:13 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] vfs: use kstrdup()

On Sat, Jul 19, 2008 at 05:19:09PM +0400, Cyrill Gorcunov wrote:
> [Cyrill Gorcunov - Sat, Jul 19, 2008 at 05:13:17PM +0400]
> [...]
> | | -			}
> | | -		}
> | | +		mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
> | |  	}
> | |  	return mnt;
> | |  }
> | | -- 
> | | 1.5.4.rc3
> | | 
> | | 
> | 
> | but kstrdup may return NULL - is it safe there?
> | Sorry if that "not smart" question.
> | 
> | 		- Cyrill -
> 
> ah, I see it is safe - sorry for noise

FWIW, it _is_ a good question.

	* is all code treating ->mnt_devname as optional?  AFAICS, there's
at least one place in NFS that doesn't.  We could treat failing allocation
the same way we treat failing allocation of vfsmount itself - callers can
cope with that already.
	* AFAICS, it should be const char *.
	* ... or perhaps we shouldn't copy it at all.  How about something
like
	struct {
		int count;
		char name[];
	}
with cloning sharing the reference and bumping the count, protecting it with
e.g. vfsmount_lock?  For setups where we have a lot of bindings/namespaces
it might be noticable.

Any takers?
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