Re: [PATCH v5 9/9] btrfs: btrfs_copy_file_range() only supports reflinks

On Wed, Oct 14, 2015 at 11:00:45PM -0700, Christoph Hellwig wrote:

On Wed, Oct 14, 2015 at 11:46:08AM -0700, Darrick J. Wong wrote:

quoted

The documentation for fallocate ought to be updated to include that as part of
guaranteeing that subsequent writes to the range won't fail due to ENOSPC,
shared blocks will be unshared.

Incidentally, btrfs leaves shared blocks alone.  OTOH, given that it's totally
COW it probably doesn't make sense to unshare blocks anyway... but maybe I
also don't want to dive into btrfs f-allocation behavior at this time. :)

Ok, so I'll rework the XFS funshare code into something that hangs off the
regular fallocate call, and get rid of the explicit 'funshare' bits.

Yes, that would be my preference.  I'd also like to understand what
exactly btrfs does in fallocate.

For which part?  The answer changes based on how many references there
are to a given fallocated region.

-chris
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