libext2s: fix unix_io with IO_FLAG_FORCE_BOUNCE flag set

The bounce read/write code would crash with a floating point exception
if alignment is set to 0.

Fixes: c001596110e8 ("libext2fs: fix unix_io's Direct I/O support")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
3 files changed