linux-kernel - Re: Regression introduced by bfcfaa77bdf0f775263e906015982a608df01c76 (vfs: use 'unsigned long' accesses for dcache name comparison and hashing)

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Message-ID: <CA+55aFzTMTXboyJxmFWrPmv6ckt5m3-9rovwg1_8Y+3Osk9uxA@mail.gmail.com>
Date:	Thu, 22 Mar 2012 13:42:27 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: Regression introduced by bfcfaa77bdf0f775263e906015982a608df01c76
 (vfs: use 'unsigned long' accesses for dcache name comparison and hashing)

On Thu, Mar 22, 2012 at 1:36 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> Guys, could you check if this fixes it?

Yup, that's the patch I was thinking of too.

But I didn't test it. And considering that apparently I don't have
anything that ever triggers this, I guess I should write some
user-space harness thing for this.

I actually wrote some *other* user-space testing functions (checking
that the hash values we generated were good), but I never tested the
"unimportant and totally obvious" full_name_hash() function.

Btw, about test harnesses: I do have a patch to the kernel that
exposes the dentry hash chains through /proc. Interesting to anybody
else? I decided that I didn't want to try to simulate the dentry
hashing in user space, since part of the final hash function is the
'parent' dentry pointer itself (the name hash part is user-spaceable,
but I wanted to see the distribution of those parent bits too).

                          Linus
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