From: Eric Sandeen Subject: Re: [PATCH] fix oops in ext4_mb_release_group_pa tracing Date: Thu, 07 Oct 2010 11:45:23 -0500 Message-ID: <4CADF923.30503@redhat.com> References: <4C6D7116.2080905@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Josef Bacik To: ext4 development Return-path: Received: from mx1.redhat.com ([209.132.183.28]:20517 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190Ab0JGQpZ (ORCPT ); Thu, 7 Oct 2010 12:45:25 -0400 Received: from int-mx08.intmail.prod.int.phx2.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o97GjPU3018109 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 7 Oct 2010 12:45:25 -0400 In-Reply-To: <4C6D7116.2080905@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On 08/19/2010 12:59 PM, Eric Sandeen wrote: > Our QA reported an oops in the ext4_mb_release_group_pa tracing, > and Josef Bacik pointed out that it was because we may have a > non-null but uninitialized ac_inode in the allocation context. > > I can reproduce it when running xfstests with ext4 tracepoints on, > on a CONFIG_SLAB_DEBUG kernel. > > We call trace_ext4_mb_release_group_pa from 2 places, > ext4_mb_discard_group_preallocations and > ext4_mb_discard_lg_preallocations > > In both cases we allocate an ac as a container just for tracing (!) > and never fill in the ac_inode. There's no reason to be assigning, > testing, or printing it as far as I can see, so just remove it from > the tracepoint. Ping on this one at least? avoid-null-dereference-in-trace_ext4_mballoc_discard is in the patch queue, this one is similar and should go with it. I'd really like to see [PATCH] don't use ext4_allocation_contexts for tracing go soon as well so we stop abusing the slab cache all day long... Thanks, -Eric > Signed-off-by: Eric Sandeen > --- > > diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h > index 01e9e00..e352c77 100644 > --- a/include/trace/events/ext4.h > +++ b/include/trace/events/ext4.h > @@ -432,7 +432,6 @@ TRACE_EVENT(ext4_mb_release_group_pa, > > TP_STRUCT__entry( > __field( dev_t, dev ) > - __field( ino_t, ino ) > __field( __u64, pa_pstart ) > __field( __u32, pa_len ) > > @@ -440,8 +439,6 @@ TRACE_EVENT(ext4_mb_release_group_pa, > > TP_fast_assign( > __entry->dev = sb->s_dev; > - __entry->ino = (ac && ac->ac_inode) ? > - ac->ac_inode->i_ino : 0; > __entry->pa_pstart = pa->pa_pstart; > __entry->pa_len = pa->pa_len; > ), > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html