mm/swapfile.c: do not skip lowest_bit in scan_swap_map() scan loop

In the second half of scan_swap_map()'s scan loop, offset is set to
si->lowest_bit and then incremented before entering the loop for the
first time, causing si->swap_map[si->lowest_bit] to be skipped.

Signed-off-by: Jamie Liu <jamieliu@google.com>
Cc: Shaohua Li <shli@fusionio.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index d443dea95c27..c6c13b050a58 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -616,7 +616,7 @@ scan:
                 }
         }
         offset = si->lowest_bit;
-        while (++offset < scan_base) {
+        while (offset < scan_base) {
                 if (!si->swap_map[offset]) {
                         spin_lock(&si->lock);
                         goto checks;
@@ -629,6 +629,7 @@ scan:
                         cond_resched();
                         latency_ration = LATENCY_LIMIT;
                 }
+                offset++;
         }
         spin_lock(&si->lock);