xfs: fix fsmap cursor handling [v2] This patchset addresses an integer overflow bug that Dave Chinner found in how fsmap handles figuring out where in the record set we left off when userspace calls back after the first call filled up all the designated record space. v2: add RVB tags This has been lightly tested with fstests. Enjoy! Signed-off-by: Darrick J. Wong <djwong@kernel.org>