From: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= Subject: Re: [PATCH] ext4: fix wrong size computation in ext4_mb_normalize_request() Date: Fri, 11 Jul 2014 09:07:23 +0200 (CEST) Message-ID: References: <1404970836-21357-1-git-send-email-wangxg.fnst@cn.fujitsu.com> <53BF5CD4.3030804@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="8323328-1152178184-1405062449=:2165" Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, mlombard@redhat.com To: Xiaoguang Wang Return-path: Received: from mx1.redhat.com ([209.132.183.28]:59166 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751154AbaGKHHg (ORCPT ); Fri, 11 Jul 2014 03:07:36 -0400 In-Reply-To: <53BF5CD4.3030804@cn.fujitsu.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323328-1152178184-1405062449=:2165 Content-Type: TEXT/PLAIN; charset=windows-1252 Content-Transfer-Encoding: 8BIT On Fri, 11 Jul 2014, Xiaoguang Wang wrote: > Date: Fri, 11 Jul 2014 11:41:08 +0800 > From: Xiaoguang Wang > To: Luk?? Czerner > Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, mlombard@redhat.com > Subject: Re: [PATCH] ext4: fix wrong size computation in > ext4_mb_normalize_request() > > Hi, > > On 07/10/2014 05:25 PM, Luk?? Czerner wrote: > > On Thu, 10 Jul 2014, Xiaoguang Wang wrote: > > > >> Date: Thu, 10 Jul 2014 13:40:36 +0800 > >> From: Xiaoguang Wang > >> To: linux-ext4@vger.kernel.org > >> Cc: tytso@mit.edu, mlombard@redhat.com, > >> Xiaoguang Wang > >> Subject: [PATCH] ext4: fix wrong size computation in > >> ext4_mb_normalize_request() > >> > >> As the member fe_len defined in struct ext4_free_extent is expressed as > >> number of clusters, the variable "size" computation is wrong, we need to > >> first translate it to block number, then to bytes. > >> > >> Signed-off-by: Xiaoguang Wang > >> --- > >> fs/ext4/mballoc.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > >> index 7f72f50..9a543b5 100644 > >> --- a/fs/ext4/mballoc.c > >> +++ b/fs/ext4/mballoc.c > >> @@ -3076,7 +3076,8 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, > >> size = 8 * 1024 * 1024; > >> } else { > >> start_off = (loff_t)ac->ac_o_ex.fe_logical << bsbits; > >> - size = ac->ac_o_ex.fe_len << bsbits; > >> + size = EXT4_C2B(EXT4_SB(ac->ac_sb), > >> + ac->ac_o_ex.fe_len) << bsbits; > > > > There is a patch out there up for more discussion which rewrites a > > whole bunch of code in ext4_mb_normalize_request(). But more > > importantly this fix, while correct is not going to change anything > > since this condition will never be run. > > Yeah, I have read your patch and related discussions, indeed this condition > would never be run, thanks for your explanation. But given that currently your > patch is not merged, still this code is wrong and should be fixed. > I'm new to ext4:) Whether should I continue to send a v2 version to fix this issue? thanks! Please do, it's still worth fixing. Thanks! -Lukas > > Regards, > Xiaoguang Wang > > > > Btw, I take back the correct part since it seems that there is a > > a possibility of overflow. This should be better. > > > > size = (loff_t)EXT4_C2B(EXT4_SB(ac->ac_sb), > > ac->ac_o_ex.fe_len) << bsbits; > > > > Thanks! > > -Lukas > > > >> } > >> size = size >> bsbits; > >> start = start_off >> bsbits; > >> > > . > > > > --8323328-1152178184-1405062449=:2165--