The found entries by find_get_pages() could be all swap entries.  In
this case we skip the entries, but make sure the skipped entries are
accounted, so we don't keep looping.

Using nr_found > nr_skip to simplify code as suggested by Eric.
Reported-and-tested-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NShaohua Li <shaohua.li@intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>