linux-kernel - Re: [PATCH] dcache: Translating dentry into pathname without taking rename

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Message-ID: <20130905043033.20292.qmail@science.horizon.com>
Date:	5 Sep 2013 00:30:33 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	waiman.long@...com
Cc:	linux@...izon.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	viro@...IV.linux.org.uk
Subject: Re: [PATCH] dcache: Translating dentry into pathname without taking rename_lock

As long as you're removing locks from prepend_name and complicating its
innards, I notice that each and every call site follows it by prepending
"/".  How about moving that into prepend_name as well?

Also, if you happen to feel like it, you can delete the slash flag
and replace it with "bptr != *buffer".

Another small tweak would be to the global_root part of the code.
You could move the is_mounted(vfsmnt) test up, and combine the tail of
that code path with the regular exit.  All you have to do is change
the !slash test to:

	if (error >= 0 && bptr == *buffer) {	/* Root directory */
		if (--blen < 0)
			error = -ENAMETOOLONG;
		else
			*--bptr = '/';
	}

This modified form is no more code than an inlined copy of prepend(),
so we haven't actually slowed the fast path, but it avoids corrupting
the return value of 0/1/2 if possible.
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