From davej Thu Mar 22 16:38:38 2012 Return-Path: linux-kernel-owner@vger.kernel.org X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on gelk.kernelslacker.org X-Spam-Level: X-Spam-Status: No, score=-1.2 required=5.0 tests=KB_DATE_CONTAINS_TAB, RCVD_IN_DNSWL_HI,T_RP_MATCHES_RCVD,UNPARSEABLE_RELAY autolearn=unavailable version=3.3.2 Received: from mail.corp.redhat.com [10.5.5.51] by gelk.kernelslacker.org with IMAP (fetchmail-6.3.21) for (single-drop); Thu, 22 Mar 2012 16:38:38 -0400 (EDT) Received: from zmta02.collab.prod.int.phx2.redhat.com (LHLO zmta02.collab.prod.int.phx2.redhat.com) (10.5.5.32) by zmail11.collab.prod.int.phx2.redhat.com with LMTP; Thu, 22 Mar 2012 16:37:12 -0400 (EDT) Received: from localhost (localhost.localdomain [127.0.0.1]) by zmta02.collab.prod.int.phx2.redhat.com (Postfix) with ESMTP id BE4B31280F5; Thu, 22 Mar 2012 16:37:12 -0400 (EDT) X-Quarantine-ID: Received: from zmta02.collab.prod.int.phx2.redhat.com ([127.0.0.1]) by localhost (zmta02.collab.prod.int.phx2.redhat.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id rVyHUDnYJs0w; Thu, 22 Mar 2012 16:37:12 -0400 (EDT) Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by zmta02.collab.prod.int.phx2.redhat.com (Postfix) with ESMTP id 34CCC1280EF; Thu, 22 Mar 2012 16:37:12 -0400 (EDT) Received: from mx1.redhat.com (ext-mx14.extmail.prod.ext.phx2.redhat.com [10.5.110.19]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id q2MKbBbO012811; Thu, 22 Mar 2012 16:37:11 -0400 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q2MIJPCS018091; Thu, 22 Mar 2012 16:37:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759738Ab2CVUhD (ORCPT + 54 others); Thu, 22 Mar 2012 16:37:03 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:35901 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758619Ab2CVUg7 (ORCPT ); Thu, 22 Mar 2012 16:36:59 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.76 #1 (Red Hat Linux)) id 1SAokk-0008Fi-MR; Thu, 22 Mar 2012 20:36:58 +0000 Date: Thu, 22 Mar 2012 20:36:58 +0000 From: Al Viro To: Linus Torvalds Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, Konrad Rzeszutek Wilk Subject: Re: Regression introduced by bfcfaa77bdf0f775263e906015982a608df01c76 (vfs: use 'unsigned long' accesses for dcache name comparison and hashing) Message-ID: <20120322203658.GC6589@ZenIV.linux.org.uk> References: <20120322183845.GA17264@phenom.dumpdata.com> <20120322200918.GZ6589@ZenIV.linux.org.uk> <20120322202445.GB6589@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120322202445.GB6589@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-RedHat-Spam-Score: -5.01 (RCVD_IN_DNSWL_HI,T_RP_MATCHES_RCVD) X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Scanned-By: MIMEDefang 2.68 on 10.5.110.19 Status: RO Content-Length: 1440 Lines: 43 On Thu, Mar 22, 2012 at 08:24:45PM +0000, Al Viro wrote: > > OK, full_name_hash()/hash_name() definitely have a mismatch and it's on the > names of length 8*n: trivial experiment shows that we have > name hash_name full_name_hash > a 61 61 > ab 6261 6261 > abc 636261 636261 > abcd 64636261 64636261 > abcdabc 64c6c4c2 64c6c4c2 > abcdabcd efcead5 c8c6c4c2 > abcdabcd9 efceb0e efceb0e > > Linus, which way do you prefer to shift it? Should hash_name() change to > match full_name_hash() or should it be the other way round? > > What happens is that you get multiplication by 9 and adding 0 in the former, > after having added the last full word. In the latter we add the last full > word, see that there's nothing left and bugger off. Guys, could you check if this fixes it? diff --git a/fs/namei.c b/fs/namei.c index 13e6a1f..7451d6f8 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1439,10 +1439,10 @@ unsigned int full_name_hash(const unsigned char *name, unsigned int len) for (;;) { a = *(unsigned long *)name; - hash *= 9; if (len < sizeof(unsigned long)) break; hash += a; + hash *= 9; name += sizeof(unsigned long); len -= sizeof(unsigned long); if (!len) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/