Re: [fstests PATCH v3] generic: add test for DAX MAP_SYNC support

[Ross Zwisler]

On Thu, Oct 26, 2017 at 07:59:39AM +0300, Amir Goldstein wrote:
> On Wed, Oct 25, 2017 at 11:47 PM, Ross Zwisler
> <ross.zwisler@xxxxxxxxxxxxxxx> wrote:
> > Add a test that exercises DAX's new MAP_SYNC flag.
> >
> > This test creates a file and writes to it via an mmap(), but never syncs
> > via fsync/msync.  This process is tracked via dm-log-writes, then replayed.
> >
> > If MAP_SYNC is working the dm-log-writes replay will show the test file
> > with 1MiB of on-media block allocations.  This is because each allocating
> > page fault included an implicit metadata sync.  If MAP_SYNC isn't working
> > (which you can test by fiddling with the parameters to mmap()) the file
> > will be smaller or missing entirely.
> >
> > Note that dm-log-writes doesn't track the data that we write via the
> > mmap(), so we can't do any data integrity checking.  We can only verify
> > that the metadata writes for the page faults happened.
> >
> > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> >
> > ---
> >
> > Changes since v2:
> >  - Fixed _require_log_writes() so that DAX will be disallowed if the
> >    version of the dm-log-writes target is older than v1.1.0.  (Amir)
> 
> It seems like your kernel patch bumped the version to 1.0.1...

Ah, yep, that's the version number that I submitted but Mike changed it to
v1.1.0 in his tree.  Here's the patch that was merged for v4.15-rc1:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers?id=98d82f48f1983ceef5c8d2f6c87bfee2918790ee

> >
> > ---
> >  .gitignore            |  1 +
> >  common/dmlogwrites    |  4 ++-
> >  common/rc             |  6 ++--
> >  src/Makefile          |  3 +-
> >  src/t_map_sync.c      | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/466     | 76 ++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/466.out |  3 ++
> >  tests/generic/group   |  1 +
> >  8 files changed, 182 insertions(+), 4 deletions(-)
> >  create mode 100644 src/t_map_sync.c
> >  create mode 100755 tests/generic/466
> >  create mode 100644 tests/generic/466.out
> >
> > diff --git a/.gitignore b/.gitignore
> > index 2014c08..9fc0695 100644
> > --- a/.gitignore
> > +++ b/.gitignore
> > @@ -119,6 +119,7 @@
> >  /src/t_getcwd
> >  /src/t_holes
> >  /src/t_immutable
> > +/src/t_map_sync
> >  /src/t_mmap_cow_race
> >  /src/t_mmap_dio
> >  /src/t_mmap_fallocate
> > diff --git a/common/dmlogwrites b/common/dmlogwrites
> > index 247c744..71d008d 100644
> > --- a/common/dmlogwrites
> > +++ b/common/dmlogwrites
> > @@ -23,8 +23,10 @@ _require_log_writes()
> >         [ -z "$LOGWRITES_DEV" -o ! -b "$LOGWRITES_DEV" ] && \
> >                 _notrun "This test requires a valid \$LOGWRITES_DEV"
> >
> > -       _exclude_scratch_mount_option dax
> >         _require_dm_target log-writes
> > +       if [[ ${DMTARGET_VER[0]} == 1 && ${DMTARGET_VER[1]} < 1 ]]; then
> > +               _exclude_scratch_mount_option dax
> > +       fi
> 
> IMO, this would be better as:
> 
>         local z=0
>         _scratch_has_mount_option dax && z=1
>         _require_dm_target log-writes 1 0 $z
> 
> Or something like that

Yep, this is nicer.  Fixed.

Thanks for the review.