linux-kernel - Re: Word-at-a-time dcache name accesses (was Re: .. anybody know of any filesystems that depend on the exact VFS 'namehash' implementation?)

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Message-ID: <CAMzpN2juEfBPcq-wKsMOG1v3ii9PNCPW6y+sT-XXAPf1jdAvkw@mail.gmail.com>
Date:	Tue, 27 Mar 2012 01:31:38 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Dave Jones <davej@...hat.com>, Brian Gerst <brgerst@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jason Garrett-Glaser <jason@...4.com>,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: Word-at-a-time dcache name accesses (was Re: .. anybody know of
 any filesystems that depend on the exact VFS 'namehash' implementation?)

On Tue, Mar 27, 2012 at 1:02 AM, Dave Jones <davej@...hat.com> wrote:
> On Tue, Mar 27, 2012 at 12:42:19AM -0400, Brian Gerst wrote:
>
>  > > I did only very limited profiling of the 32-bit case, but it's really
>  > > just four cheap ALU instructions there and didn't really show up at
>  > > all in the limited profiles I did. And at least I checked that the
>  > > code worked. I have to say that the advantage of "vectorizing" this
>  > > code is obviously much less if you can only do 4-byte "vectors", so I
>  > > didn't actually time whether the patch *improves* anything on x86-32.
>  > >
>  >
>  > This patch is causing my system (x86-64, Fedora 16) to fail to boot
>  > when DEBUG_PAGEALLOC=n.  No oops, but these error messages were in the
>  > log for the bad kernel:
>
> I saw this too, it was fixed by f132c5be05e407a99cf582347a2ae0120acd3ad7 for me.
> Does your kernel have that commit ?
>
>        Dave
>
>

Yes, I see that commit.  It looks like I have a different bug that is
preventing the current head from booting then.  Bisecting brought me
to this commit instead.

--
Brian Gerst
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