From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D0676C433E0 for ; Wed, 24 Jun 2020 12:43:44 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7C6CD20836 for ; Wed, 24 Jun 2020 12:43:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZKFjoN3Z" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C6CD20836 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42476 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jo4kh-0004Sk-Iz for qemu-devel@archiver.kernel.org; Wed, 24 Jun 2020 08:43:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60742) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jo4js-0003wk-Kh for qemu-devel@nongnu.org; Wed, 24 Jun 2020 08:42:52 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:47432 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jo4jr-0008QK-73 for qemu-devel@nongnu.org; Wed, 24 Jun 2020 08:42:52 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593002570; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=heckdSvscLlWFLOgaeuphmvQ8XCTcmZk5n5LB93sWXk=; b=ZKFjoN3ZSu85cLs8ztxERnPN9zx6xDfHqUd3OWHi5Cmfrh9U8F1yEjVNvAvD5gKwVeEwO7 6WaORZ2QqyYPAXEZ6jh2RDgIfTXupbvPXs74PmnC8/xGtU+dqaoLFf1m81a8jcUgw0WpPe kQcne3Nhl5R4uMvwTlQRvZPjebR/9Z0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-73-Epz4UNt1NJOF5YMYhdGwnw-1; Wed, 24 Jun 2020 08:42:47 -0400 X-MC-Unique: Epz4UNt1NJOF5YMYhdGwnw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EE6F280400B; Wed, 24 Jun 2020 12:42:45 +0000 (UTC) Received: from linux.fritz.box (ovpn-114-87.ams2.redhat.com [10.36.114.87]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D45BC101E247; Wed, 24 Jun 2020 12:42:44 +0000 (UTC) Date: Wed, 24 Jun 2020 14:42:43 +0200 From: Kevin Wolf To: Eric Blake Subject: Re: [PATCH 2/2] vvfat: Fix array_remove_slice() Message-ID: <20200624124243.GC9253@linux.fritz.box> References: <20200623175534.38286-1-kwolf@redhat.com> <20200623175534.38286-3-kwolf@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.120; envelope-from=kwolf@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/24 02:33:25 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: nhuck15@gmail.com, qemu-devel@nongnu.org, qemu-block@nongnu.org, ppandit@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 23.06.2020 um 20:30 hat Eric Blake geschrieben: > On 6/23/20 12:55 PM, Kevin Wolf wrote: > > array_remove_slice() calls array_roll() with array->next - 1 as the > > destination index. This is only correct for count == 1, otherwise we're > > writing past the end of the array. array->next - count would be correct. > > > > However, this is the only place ever calling array_roll(), so this > > rather complicated operation isn't even necessary. > > > > Fix the problem and simplify the code by replacing it with a single > > memmove() call. array_roll() can now be removed. > > > > Reported-by: Nathan Huckleberry > > Signed-off-by: Kevin Wolf > > --- > > block/vvfat.c | 42 +++++------------------------------------- > > 1 file changed, 5 insertions(+), 37 deletions(-) > > > > diff --git a/block/vvfat.c b/block/vvfat.c > > index 2fab371258..d6e464c595 100644 > > --- a/block/vvfat.c > > +++ b/block/vvfat.c > > @@ -140,48 +140,16 @@ static inline void* array_insert(array_t* array,unsigned int index,unsigned int > > return array->pointer+index*array->item_size; > > } > > -/* this performs a "roll", so that the element which was at index_from becomes > > - * index_to, but the order of all other elements is preserved. */ > > -static inline int array_roll(array_t* array,int index_to,int index_from,int count) > > If I understand the intent from just the comment, the old code would take a > directory listing of six files: > > ABCDEF > > and on the request to delete file C, would produce: > > ABFDE > > by moving just F, instead of all of DEF. I think what the old code did was actually moving C, not F, so you get: ABDEFC And then you reduce the array size by one so that C isn't visible any more. My code preserves this behaviour, except that the invisible final element is a copy of F instead C now. Kevin