Re: [PATCH V2 0/3] fstests: fixes for 64k pages and dax

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Feb 20, 2020 at 03:06:29PM -0500, Jeff Moyer wrote:
> This set of patches fixes a few false positives I encountered when
> testing DAX on ppc64le (which has a 64k page size).
> 
> Patch 1 is actually not specific to non-4k page sizes.  Currently,
> each individual dm rc file checks for the presence of the DAX mount
> option, and _notruns the test as part of the initializtion.  This
> doesn't work for the snapshot target.  Moving the check into the
> _require_dm_target fixes the problem, and keeps from the cut-n-paste
> of boilerplate.
> 
> Patches 2 and 3 get rid of hard coded block/page sizes in the tests.
> They run just fine on 64k pages and 64k block sizes.
> 
> Even after these patches, there are many more tests that fail in the
> following configuration:
> 
> MKFS_OPTIONS="-b size=65536 -m reflink=0" MOUNT_OPTIONS="-o dax"
> 
> One class of failures is tests that create a really small file system
> size.  Some of those tests seem to require the very small size, but
> others seem like they could live with a slightly bigger size that
> would then fit the log (the typical failure is a mkfs failure due to
> not enough blocks for the log).  For the former case, I'm tempted to
> send patches to _notrun those tests, and for the latter, I'd like to
> bump the file system sizes up.  300MB seems to be large enough to
> accommodate the log.  Would folks be opposed to those approaches?

Seems fine to me.  Do we have a helper function to compute (or maybe
just format) the minimum supported filesystem size for the given
MKFS_OPTIONS?

> Another class of failure is tests that either hard-code a block size
> to trigger a specific error case, or that test a multitude of block
> sizes.  I'd like to send a patch to _notrun those tests if there is
> a user-specified block size.  That will require parsing the MKFS_OPTIONS
> based on the fs type, of course.  Is that something that seems
> reasonable?

I think it's fine to _notrun a test that requires a specific blocksize
when when that blocksize is not supported by the system under test.

The ones that cycle through a range of block sizes, not so much--I guess
the question here is can we distinguish "test only this blocksize" vs
"default to this block size"?  And do we want to?

--D

> I will follow up with a series of patches to implement those changes
> if there is consensus on the approach.  These first three seemed
> straight-forward to me, so that's where I'm starting.
> 
> Changes in v2:
> - patch 2: remove the boilerplate from all dm rc files (Zorro Lang)
> - cc fstests (thanks, Dave)
> 
> [PATCH V2 1/3] dax/dm: disable testing on devices that don't support
> [PATCH V2 2/3] t_mmap_collision: fix hard-coded page size
> [PATCH V2 3/3] xfs/300: modify test to work on any fs block size
>