114 lines
4.8 KiB
Diff
114 lines
4.8 KiB
Diff
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From davej Thu Mar 22 16:38:38 2012
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id 1SAokk-0008Fi-MR; Thu, 22 Mar 2012 20:36:58 +0000
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Date: Thu, 22 Mar 2012 20:36:58 +0000
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From: Al Viro <viro@ZenIV.linux.org.uk>
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To: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com,
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Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Subject: Re: Regression introduced by
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bfcfaa77bdf0f775263e906015982a608df01c76 (vfs: use 'unsigned long' accesses
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for dcache name comparison and hashing)
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Message-ID: <20120322203658.GC6589@ZenIV.linux.org.uk>
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References: <20120322183845.GA17264@phenom.dumpdata.com>
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<20120322200918.GZ6589@ZenIV.linux.org.uk>
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<20120322202445.GB6589@ZenIV.linux.org.uk>
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X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24
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X-Scanned-By: MIMEDefang 2.68 on 10.5.110.19
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Status: RO
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Content-Length: 1440
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Lines: 43
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On Thu, Mar 22, 2012 at 08:24:45PM +0000, Al Viro wrote:
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>
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> OK, full_name_hash()/hash_name() definitely have a mismatch and it's on the
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> names of length 8*n: trivial experiment shows that we have
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> name hash_name full_name_hash
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> a 61 61
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> ab 6261 6261
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> abc 636261 636261
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> abcd 64636261 64636261
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> abcdabc 64c6c4c2 64c6c4c2
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> abcdabcd efcead5 c8c6c4c2
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> abcdabcd9 efceb0e efceb0e
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>
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> Linus, which way do you prefer to shift it? Should hash_name() change to
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> match full_name_hash() or should it be the other way round?
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>
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> What happens is that you get multiplication by 9 and adding 0 in the former,
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> after having added the last full word. In the latter we add the last full
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> word, see that there's nothing left and bugger off.
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Guys, could you check if this fixes it?
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diff --git a/fs/namei.c b/fs/namei.c
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index 13e6a1f..7451d6f8 100644
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--- a/fs/namei.c
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+++ b/fs/namei.c
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@@ -1439,10 +1439,10 @@ unsigned int full_name_hash(const unsigned char *name, unsigned int len)
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for (;;) {
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a = *(unsigned long *)name;
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- hash *= 9;
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if (len < sizeof(unsigned long))
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break;
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hash += a;
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+ hash *= 9;
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name += sizeof(unsigned long);
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len -= sizeof(unsigned long);
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if (!len)
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--
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