Re: [PATCH] generic: test which tries to exercise AIO/DIO into unwritten space

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Mar 02, 2021 at 11:20:06AM +0800, Su Yue wrote:
> On Tue, Mar 2, 2021 at 2:10 AM Theodore Ts'o <tytso@mit.edu> wrote:
> >
> > On Mon, Mar 01, 2021 at 09:14:40AM -0800, Darrick J. Wong wrote:
> > > On Wed, Feb 10, 2021 at 03:58:18PM -0500, Theodore Ts'o wrote:
> > > > This test verifies that the an unwritten extent is properly marked as
> > > > written after writing into it.
> > > >
> > > > There was a hard-to-hit bug which would occasionally trigger with ext4
> > > > for which this test was a reproducer.  This has been fixed after
> > > > moving ext4 to use iomap for Direct I/O's, although as of this
> > > > writing, there are still some occasional failures on ext4 when block
> > > > size < page size.
> > >
> > > Are there still failures?
> >
> > Yes.  It's on Ritesh's todo list, but I don't believe it's bubbled up
> > to the top of his list.
> >
> > The failure rate is substantially less than what I had been seeing
> > with 4k block sizes before the move to iomap, and in practice it was
> > hard to hit in production.  We noticed on Google data center workloads
> > (but even then it was impossible to reliably repro before I found this
> > fio recipe); as far as I know no one else had reported seeing this
> > problem.
> >
> > So in summary, as of this writing, on 1k and 2k block sizes, this test
> > is still occasionally failing for ext4 (but not xfs, where it reliably
> > passes).  On 4k block sizes on x86 with ext4, this test is still
> > failing in on 5.4 and earler kernels, unless someone has managed to
> > backport DIO iomap support for ext4 into an enterprise linux kernel.
> >
> But both xfs and ext4 100% fail in v5.12-rc1 with 4k block size and 4k page
> size on x86_64. The test itself should be okay because btrfs passes.
> xfstests-dev version is 8cbc48b460b6 applied this patch. logs are attached.

Is this generic/623?  That test is new, and I've noticed it'll fail if
you have coredumps enabled because the test tries to induce a SIGBUS.

--D

> 
> # fio --version
> fio-3.25
> 
> #cat local.config
> export TEST_DEV=/dev/mapper/test-1
> export TEST_DIR=/mnt/test
> export SCRATCH_DEV_POOL="/dev/mapper/test-[2-6]"
> export SCRATCH_MNT=/mnt/scratch
> export LOGWRITES_DEV="/dev/mapper/test-7"
> export KEEP_DMESG=yes
> 
> >                                         - Ted