iomap: constrain the file range passed to iomap_file_unshare

[ Upstream commit a311a08a ]

File contents can only be shared (i.e. reflinked) below EOF, so it makes
no sense to try to unshare ranges beyond EOF.  Constrain the file range
parameters here so that we don't have to do that in the callers.

Fixes: 5f4e5752 ("fs: add iomap_file_dirty")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20241002150213.GC21853@frogsfrogsfrogs


Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>