Segfaults--they're back!

Segfaults--they're back!

[Gary Hawco]

Segfaults have returned with snapshots compiled after 070908--0010hrs GMT.

That one worked fine.

The next one I tried (070908/0025hrs GMT) caused segfaults in both Gentoo &
Slackware (a first for Slackware) when trying to untar
linux-2.6.26-rc9.tar.bz2 tarball)

I then rolled back two snapshots to 070908/0012hrs GMT) and it segfaulted
in both operating systems doing same untarring function.

So, apparently, since 0010snapshot
(ext4-patch-queue-bfb23cf4cd345552c774142cb10ac1225caf35f5.tar.gz) works fine

and 0012snapshot
(ext4-patch-queue-be66b0c5c3f4293176301c0ddcb8db95b0576cb4.tar.gz)
segfaults, the 
Add ext4-fix-mb_find_next_bit-return.patch must be the culprit.

Thanks,
Gary

P.S. The latest snapshot from today @ 0303hrs GMT segfaults as well.

Re: Segfaults--they're back!

[Mingming Cao]

在 2008-07-09三的 15:00 +0000，Gary Hawco写道：
> Segfaults have returned with snapshots compiled after 070908--0010hrs GMT.
> 
> That one worked fine.
> 
> The next one I tried (070908/0025hrs GMT) caused segfaults in both Gentoo &
> Slackware (a first for Slackware) when trying to untar
> linux-2.6.26-rc9.tar.bz2 tarball)
> 
> I then rolled back two snapshots to 070908/0012hrs GMT) and it segfaulted
> in both operating systems doing same untarring function.
> 
> So, apparently, since 0010snapshot
> (ext4-patch-queue-bfb23cf4cd345552c774142cb10ac1225caf35f5.tar.gz) works fine
> 
> and 0012snapshot
> (ext4-patch-queue-be66b0c5c3f4293176301c0ddcb8db95b0576cb4.tar.gz)
> segfaults, the 
> Add ext4-fix-mb_find_next_bit-return.patch must be the culprit.
> 

Thanks for reporting this, 
commit be66b0c5c3f4293176301c0ddcb8db95b0576cb4 added
ext4-fix-mb_find_next_bit-return.patch

I have dropped  this patch from patch queue, could you please check if
the segment fault goes away?


Mingming
> Thanks,
> Gary
> 
> P.S. The latest snapshot from today @ 0303hrs GMT segfaults as well.
> 

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Re: Segfaults--they're back!

[Aneesh Kumar K.V]

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.
> 
> The next one I tried (070908/0025hrs GMT) caused segfaults in both Gentoo &
> Slackware (a first for Slackware) when trying to untar
> linux-2.6.26-rc9.tar.bz2 tarball)
> 
> I then rolled back two snapshots to 070908/0012hrs GMT) and it segfaulted
> in both operating systems doing same untarring function.
> 
> So, apparently, since 0010snapshot
> (ext4-patch-queue-bfb23cf4cd345552c774142cb10ac1225caf35f5.tar.gz) works fine
> 
> and 0012snapshot
> (ext4-patch-queue-be66b0c5c3f4293176301c0ddcb8db95b0576cb4.tar.gz)
> segfaults, the 
> Add ext4-fix-mb_find_next_bit-return.patch must be the culprit.

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# 

-aneesh

Re: Segfaults--they're back!

[Theodore Tso]

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