staging: ion: Add private buffer flag to skip page pooling on free

Currently, when we free a buffer it might actually just go back into a
heap-specific page pool rather than going back to the system. This poses
a problem because sometimes (like when we're running a shrinker in low
memory conditions) we need to force the memory associated with the
buffer to truly be relinquished to the system rather than just going
back into a page pool.

There isn't a use case for this flag by Ion clients, so make it a
private flag. The main use case right now is to provide a mechanism for
the deferred free code to force stale buffers to bypass page pooling.

Cc: Colin Cross <ccross@android.com>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
[jstultz: Minor commit subject tweak]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 16 insertions, 3 deletions

diff --git a/drivers/staging/android/ion/ion_heap.c b/drivers/staging/android/ion/ion_heap.c
index 49ace13ac545..bdc6a28ba8c9 100644
--- a/drivers/staging/android/ion/ion_heap.c
+++ b/drivers/staging/android/ion/ion_heap.c
@@ -178,7 +178,8 @@ size_t ion_heap_freelist_size(struct ion_heap *heap)
 	return size;
 }
 
-size_t ion_heap_freelist_drain(struct ion_heap *heap, size_t size)
+static size_t _ion_heap_freelist_drain(struct ion_heap *heap, size_t size,
+				bool skip_pools)
 {
 	struct ion_buffer *buffer;
 	size_t total_drained = 0;
@@ -197,6 +198,8 @@ size_t ion_heap_freelist_drain(struct ion_heap *heap, size_t size)
 					  list);
 		list_del(&buffer->list);
 		heap->free_list_size -= buffer->size;
+		if (skip_pools)
+			buffer->private_flags |= ION_PRIV_FLAG_SHRINKER_FREE;
 		total_drained += buffer->size;
 		spin_unlock(&heap->free_lock);
 		ion_buffer_destroy(buffer);
@@ -207,6 +210,16 @@ size_t ion_heap_freelist_drain(struct ion_heap *heap, size_t size)
 	return total_drained;
 }
 
+size_t ion_heap_freelist_drain(struct ion_heap *heap, size_t size)
+{
+	return _ion_heap_freelist_drain(heap, size, false);
+}
+
+size_t ion_heap_freelist_shrink(struct ion_heap *heap, size_t size)
+{
+	return _ion_heap_freelist_drain(heap, size, true);
+}
+
 static int ion_heap_deferred_free(void *data)
 {
 	struct ion_heap *heap = data;
@@ -278,10 +291,10 @@ static unsigned long ion_heap_shrink_scan(struct shrinker *shrinker,
 
 	/*
 	 * shrink the free list first, no point in zeroing the memory if we're
-	 * just going to reclaim it
+	 * just going to reclaim it. Also, skip any possible page pooling.
 	 */
 	if (heap->flags & ION_HEAP_FLAG_DEFER_FREE)
-		freed = ion_heap_freelist_drain(heap, to_scan * PAGE_SIZE) /
+		freed = ion_heap_freelist_shrink(heap, to_scan * PAGE_SIZE) /
 				PAGE_SIZE;
 
 	to_scan -= freed;