Re: [PATCH 10/10] swapext: make sure that we don't swap unwritten extents unless they're part of a rt extent(??)

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

On Tue, Jun 18, 2024 at 11:11:26PM -0700, Christoph Hellwig wrote:
> On Mon, Jun 17, 2024 at 05:49:21PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> 
> Can you add a commit message explaining what this test does and why
> you wrote it?

Whoops, another one escaped:

exchangerange: make sure that we don't swap unwritten extents unless they're part of a rt extent

By default, the FILE1_WRITTEN flag for the EXCHANGERANGE ioctl isn't
supposed to touch anything except for written extents.  In other words,
it shouldn't exchange delalloc reservations, unwritten preallocations,
or holes.  The XFS implementation flushes dirty pagecache to disk so
there should never be delalloc reservations running through the
exchangerange machinery, but there can be unwritten extents.

Hence, write a test to make sure that unwritten extents don't get moved
around.  This test opts itself out for realtime filesystems where the
allocation unit is larger than 1 fsblock because xfs has to move full
allocation units, and that requires exchanging of partially written rt
extents.

--D