Re: [PATCH v6 1/3] xfstests: btrfs: add functions to create dm-error device

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Dave,

On 08/21/2015 05:45 AM, Dave Chinner wrote:
On Thu, Aug 20, 2015 at 03:09:05PM +0800, Anand Jain wrote:

  (thanks for the off-ML emails from the people who helped me
  to understand).

Dave,

  looks like you are suggesting something like..

-------
+_dmerror_mount_options()
+{
+       _scratch_options mount
+       echo $SCRATCH_OPTIONS $MOUNT_OPTIONS $SELINUX_MOUNT_OPTIONS \
+                                       $* $DMERROR_DEV $SCRATCH_MNT
+}
+
+_dmerror_mount()
+{
+       _mount -t $FSTYP `_dmerror_mount_options $*`
+}
--------

Very close. :)

You've got the structure right, but missed one more thing: the
options are still cut'n'paste from _scratch_mount_options, and so
should be /factored/ into a common function...

_scratch_options is only useful to XFS to set external log/realtime
devices, and we don't want to do that for the dmerror device.
Everthing else is almost the same as _scratch_mount_options(),
however.  So:

# Used for mounting non-scratch devices (e.g. loop, dm constructs)
# with the safe set of scratch mount options (e.g. loop image may be
# hosted on $SCRATCH_DEV, so can't use external scratch devices).
_common_dev_mount_options()
{
	echo $MOUNT_OPTIONS $SELINUX_MOUNT_OPTIONS $*
}

_scratch_mount_options()
{
	_scratch_options mount

	echo `_common_dev_mount_options $*` $SCRATCH_OPTIONS \
					    $SCRATCH_DEV $SCRATCH_MNT

}


_dmerror_mount_options()
{
        echo `_common_dev_mount_options $*` $DMERROR_DEV $SCRATCH_MNT
}


  this would make test cases nice and sleek. Thanks. I have this in v8.


And to demonstrate why factoring like this is useful, this can also
be applied to _mount_flakey(), and we could also replace most of the
open-coded loop device mounts with a generic "mount device" function
like:

  yes indeed. I suggest if these could be handled in a separate patch
  as this would deviate from the intentions of this patch set ?

Thanks, Anand


_mount_dev()
{
	_mount `_common_dev_mount_options $*`
}

and call it like:

_mount_dev $LOOP_DEV $MNT_POINT

or even

_mount_dev -o loop $MNT_POINT

We can then take it further: if we have a _mount_dev() wrapper we
can factor _common_dev_mount_options() from all the
_*_mount_options() functions. i.e:

_scratch_mount_options()
{
	_scratch_options mount

	echo $SCRATCH_OPTIONS $SCRATCH_DEV $SCRATCH_MNT
}

_scratch_mount()
{
	_mount_dev $* `_scratch_mount_options`
}

The result is we end up with a much cleaner set of mount functions
that are more generic, more extensible and easier to use, as well as
being more maintainable....

  Sorry that the word 'should mirror _scratch_mount()' confused me.

Ok, I'll try to be more clear in future.

Cheers,

Dave.

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