hibernation: freeze swap at hibernation

When taking a memory snapshot in hibernate_snapshot(), all (directly
called) memory allocations use GFP_ATOMIC.  Hence swap misusage during
hibernation never occurs.

But from a pessimistic point of view, there is no guarantee that no page
allcation has __GFP_WAIT.  It is better to have a global indication "we
enter hibernation, don't use swap!".

This patch tries to freeze new-swap-allocation during hibernation.  (All
user processes are frozenm so swapin is not a concern).

This way, no updates will happen to swap_map[] between
hibernate_snapshot() and save_image().  Swap is thawed when swsusp_free()
is called.  We can be assured that swap corruption will not occur.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Hugh Dickins <hughd@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Ondrej Zary <linux@rainbow-software.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index e6a5bdf61a37..5d0059eed3e4 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -136,10 +136,10 @@ sector_t alloc_swapdev_block(int swap)
 {
         unsigned long offset;
 
-        offset = swp_offset(get_swap_page_of_type(swap));
+        offset = swp_offset(get_swap_for_hibernation(swap));
         if (offset) {
                 if (swsusp_extents_insert(offset))
-                        swap_free(swp_entry(swap, offset));
+                        swap_free_for_hibernation(swp_entry(swap, offset));
                 else
                         return swapdev_block(swap, offset);
         }
@@ -163,7 +163,7 @@ void free_all_swap_pages(int swap)
                 ext = container_of(node, struct swsusp_extent, node);
                 rb_erase(node, &swsusp_extents);
                 for (offset = ext->start; offset <= ext->end; offset++)
-                        swap_free(swp_entry(swap, offset));
+                        swap_free_for_hibernation(swp_entry(swap, offset));
 
                 kfree(ext);
         }