Port fix to the off-by-one in find_next_usable_block's memscan from ext2 to
ext3; but it didn't cause a serious problem for ext3 because the additional
ext3_test_allocatable check rescued it from the error.
Signed-off-by: Mingming Cao <cmm@us.ibm.com> Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>