mm/swap_state.c: simplify total_swapcache_pages() with get_swap_device()

total_swapcache_pages() may race with swapper_spaces[] allocation and
freeing.  Previously, this is protected with a swapper_spaces[] specific
RCU mechanism.  To simplify the logic/code complexity, it is replaced with
get/put_swap_device().  The code line number is reduced too.  Although not
so important, the swapoff() performance improves too because one
synchronize_rcu() call during swapoff() is deleted.

[[email protected]: fix bad swap file entry warning]
  Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: "Huang, Ying" <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Tested-by: Mike Kravetz <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Tim Chen <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Daniel Jordan <[email protected]>
Cc: Andrea Parri <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions