mm: Export nr_swap_pages

Some modules, like i915.ko, use swappable objects and may try to swap
them out under memory pressure (via the shrinker). Before doing so, they
want to check using get_nr_swap_pages() to see if any swap space is
available as otherwise they will waste time purging the object from the
device without recovering any memory for the system. This requires the
nr_swap_pages counter to be exported to the modules.

Signed-off-by: Chris Wilson <[email protected]>
Cc: "Goel, Akash" <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: [email protected]
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]
Acked-by: Andrew Morton <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Signed-off-by: Daniel Vetter <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 58877312cf6b..2d259fdb2347 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -48,6 +48,12 @@ static sector_t map_swap_entry(swp_entry_t, struct block_device**);
 DEFINE_SPINLOCK(swap_lock);
 static unsigned int nr_swapfiles;
 atomic_long_t nr_swap_pages;
+/*
+ * Some modules use swappable objects and may try to swap them out under
+ * memory pressure (via the shrinker). Before doing so, they may wish to
+ * check to see if any swap space is available.
+ */
+EXPORT_SYMBOL_GPL(nr_swap_pages);
 /* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
 long total_swap_pages;
 static int least_priority;