linux-ext4 - Re: Segfaults--they're back!

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Message-ID: <20080710110230.GA8603@mit.edu>
Date:	Thu, 10 Jul 2008 07:02:30 -0400
From:	Theodore Tso <tytso@....edu>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	Gary Hawco <ghawco@....net>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	Mingming <cmm@...ibm.com>
Subject: Re: Segfaults--they're back!

On Thu, Jul 10, 2008 at 10:51:50AM +0530, Aneesh Kumar K.V wrote:
> On Wed, Jul 09, 2008 at 03:00:04PM +0000, Gary Hawco wrote:
> > Segfaults have returned with snapshots compiled after 070908--0010hrs GMT.
> > 
> > That one worked fine.

Is this a kernel or userspace segfault?  i.e., is there a kernel oops
message?  If so, can you send us the oops message?  It's really really
useful to have it.  Also, can you send us a dumpe2fs of the filesystem
which ou were writing to?  Some of the bugs which we've been finding
are specific to a 1k block filesystem, for example, and sometimes that
can help narrow down the bug.

> Is your file system full when this happens ? Which user space call cause
> the segfault ? An strace should be able to help you find that. We
> actually have modified ext4 to give SIGBUS when we hit ENOSPC during
> mmap write. For ex:
> 
> root:/ext4# /root/mmaptest ./test4  0 100
> mmaping 0 to 100
> Bus error (core dumped)
> root:/ext4# 

What Aneesh is talking about here is a userspace core dump which is
normal, if the filesystem is full.  I'm not sure that's what you're
referring to assuming that "they're back" means you're referring to a
kernel oops.

Regards,

						- Ted
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