Re: [PATCH] xfs: add regression test for DAX mount option usage

[Ross Zwisler <ross.zwisler@linux.intel.com>]

On Fri, Sep 08, 2017 at 03:21:53PM -0600, Ross Zwisler wrote:
> This adds a regression test for the following kernel patch:
> 
>   xfs: always use DAX if mount option is used
> 
> This test will also pass with kernel v4.14-rc1 and beyond because the XFS
> DAX I/O mount option has been disabled (but not removed), so the
> "chattr -x" to turn off DAX doesn't actually do anything.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Suggested-by: Christoph Hellwig <hch@infradead.org>

<>

> +# disable tracing, clear the existing trace buffer and turn on dax tracepoints
> +echo 0 > /sys/kernel/debug/tracing/tracing_on
> +echo > /sys/kernel/debug/tracing/trace
> +echo 1 > /sys/kernel/debug/tracing/events/fs_dax/enable

I think I can do a better job of:

a) detecting whether debugfs is present, and if not just bail the test as not
run

b) recording the current state of the debugfs (tracing_on, fs_dax/enable),
doing what I need to do, then restoring the previous state.

Before I work on a v2, though, I'd love to get feedback on whether or not
using tracepoints is okay in fstests.