xfs: fix logdev fsmap query result filtering

xfs: fix logdev fsmap query result filtering

[ Upstream commit a949a1c2a198e048630a8b0741a99b85a5d88136 ]

The external log device fsmap backend doesn't have an rmapbt to query,
so it's wasteful to spend time initializing the rmap_irec objects.
Worse yet, the log could (someday) be longer than 2^32 fsblocks, so
using the rmap irec structure will result in integer overflows.

Fix this mess by computing the start address that we want from keys[0]
directly, and use the daddr-based record filtering algorithm that we
also use for rtbitmap queries.

Fixes: e89c041338ed ("xfs: implement the GETFSMAP ioctl")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Acked-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>