On Fri, Nov 15, 2019 at 09:20:33AM -0500, Theodore Y. Ts'o wrote:
> On Fri, Nov 15, 2019 at 11:02:22AM +0100, Jan Kara wrote:
> > On Thu 14-11-19 23:52:23, Eric Biggers wrote:
> > > On Tue, Nov 05, 2019 at 05:44:26PM +0100, Jan Kara wrote:
> > > > static inline int jbd2_handle_buffer_credits(handle_t *handle)
> > > > {
> > > > - return handle->h_buffer_credits;
> > > > + journal_t *journal = handle->h_transaction->t_journal;
> > > > +
> > > > + return handle->h_buffer_credits -
> > > > + DIV_ROUND_UP(handle->h_revoke_credits_requested,
> > > > + journal->j_revoke_records_per_block);
> > > > }
> > >
> > > This patch is causing a crash with 'kvm-xfstests -c dioread_nolock ext4/024'.
> > > Looks like this code incorrectly assumes that h_transaction is always valid
> > > rather than the other member of the union, h_journal.
> >
> > Right, thanks for the report! Just out of curiosity: You have to have that
> > tracepoint enabled for the crash to trigger, don't you? Because I'm pretty
> > sure I did dioread_nolock runs...
>
> I've been *definitely* been doing dioread_nolock runs (including two
> last night), with no failures.
>
> ext4/dioread_nolock: 485 tests, 40 skipped, 5142 seconds
>
No I didn't enable the tracepoint. I think the difference is that I had
CONFIG_UBSAN enabled. I get the crash if I use the following kconfig:
curl -o .config 'https://git.kernel.org/pub/scm/fs/ext2/xfstests-bld.git/plain/kernel-configs/x86_64-config-5.4'
echo CONFIG_UBSAN=y >> .config
make olddefconfig
... but not if I don't enable UBSAN.
No idea why UBSAN makes a difference here, though. I'm using gcc 9.2.0.
- Eric
