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

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Message-ID: <20130905041959.GN13318@ZenIV.linux.org.uk>
Date:	Thu, 5 Sep 2013 05:20:00 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Waiman Long <waiman.long@...com>,
	Scott J Norton <scott.norton@...com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"Chandramouleeswaran, Aswin" <aswin@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dcache: Translating dentry into pathname without taking
 rename_lock

On Wed, Sep 04, 2013 at 07:48:14PM -0700, Linus Torvalds wrote:
>  - use the name length as a maximum
> 
>  - do a byte-at-a-time copy, stopping at a zero (it's going to be
> faster than memchr anyway)
> 
> Then, later on, we can do one that does a word-at-a-time using the
> CONFIG_DCACHE_WORD_ACCESS magic: we know dentry names are always
> word-aligned, and we have an efficient "has_zero()" function for
> finding zero bytes in a word.

Umm...  Dentry names are word-aligned, but the place where we copy them
doesn't have to be.  OTOH, DCACHE_WORD_ACCESS is for architectures where
unaligned stores are fine, so...
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