From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Sandeen Subject: Re: ext4: Do not dec quota for reserved blocks on error paths v2 Date: Tue, 04 May 2010 15:22:45 -0500 Message-ID: <4BE08215.2050603@redhat.com> References: <87633dcxhp.fsf@openvz.org> <87bpd3ecya.fsf@openvz.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-ext4@vger.kernel.org To: Dmitry Monakhov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50814 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933863Ab0EDUWu (ORCPT ); Tue, 4 May 2010 16:22:50 -0400 In-Reply-To: <87bpd3ecya.fsf@openvz.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: Dmitry Monakhov wrote: > If we have failed some where inside ext4_get_blocks() internals we may > have allocated some new blocks, which was not yet claimed to quota. > We have to free such blocks, but without touching quota. Quota will > be updated later on exit from ext4_get_blocks(). > There are two possible ways to understand what we have to skip quota update: > 1) Caller pass corresponding flag to ext4_free_blocks() > 2) check that free_blocks() was indirectly called by get_blocks() > (i.e EXT4_I(inode)->i_delalloc_reserved_flag is set) > Second is simpler, but may result in unpredictable consequences later. > So i've chosen the first one, because caller must know which blocks it > is freeing. > > Eric, please take your attention to metadata blocks handling when > you will work on new versing of "ext4: don't use quota reservation for > speculative metadata blocks" patch. > > The bug happens on heavily loaded node, or with 227'th xfstestcase and hm which test? 227 is xfs-only... -Eric > result in incorrect i_blocks (less than expected). So truncation for > that file result in i_blocks overflow. > Seems this was the last bug which was easily triggered by 227'th testcase. > >