[PATCH AUTOSEL 5.6 240/606] Revert "virtio-balloon: Revert "virtio-balloon: Switch back to OOM handler for VIRTIO_BALLOON_F_DEFLATE_ON_OOM""

Sasha Levin
2020-06-09T00:06:20Z

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit 37681282be8e89ae8baf26753bf489837d74e08e which is
commit 835a6a649d0dd1b1f46759eb60fff2f63ed253a7 upstream.

Jiri and David agree that it is not needed in the 5.6.y tree, so revert
it.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: David Hildenbrand <david@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/virtio/virtio_balloon.c | 107 +++++++++++++-------------------
1 file changed, 44 insertions(+), 63 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 341458fd95ca..44375a22307b 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -14,6 +14,7 @@
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/balloon_compaction.h>
+#include <linux/oom.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/mount.h>
@@ -27,7 +28,9 @@
*/
#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
-#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
+/* Maximum number of (4k) pages to deflate on OOM notifications. */
+#define VIRTIO_BALLOON_OOM_NR_PAGES 256
+#define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80

#define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
__GFP_NOMEMALLOC)
@@ -112,8 +115,11 @@ struct virtio_balloon {
/* Memory statistics */
struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];

- /* To register a shrinker to shrink memory upon memory pressure */
+ /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
struct shrinker shrinker;
+
+ /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
+ struct notifier_block oom_nb;
};

static struct virtio_device_id id_table[] = {
@@ -788,50 +794,13 @@ static unsigned long shrink_free_pages(struct virtio_balloon *vb,
return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
}

-static unsigned long leak_balloon_pages(struct virtio_balloon *vb,
- unsigned long pages_to_free)
-{
- return leak_balloon(vb, pages_to_free * VIRTIO_BALLOON_PAGES_PER_PAGE) /
- VIRTIO_BALLOON_PAGES_PER_PAGE;
-}
-
-static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
- unsigned long pages_to_free)
-{
- unsigned long pages_freed = 0;
-
- /*
- * One invocation of leak_balloon can deflate at most
- * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
- * multiple times to deflate pages till reaching pages_to_free.
- */
- while (vb->num_pages && pages_freed < pages_to_free)
- pages_freed += leak_balloon_pages(vb,
- pages_to_free - pages_freed);
-
- update_balloon_size(vb);
-
- return pages_freed;
-}
-
static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
struct shrink_control *sc)
{
- unsigned long pages_to_free, pages_freed = 0;
struct virtio_balloon *vb = container_of(shrinker,
struct virtio_balloon, shrinker);

- pages_to_free = sc->nr_to_scan;
-
- if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
- pages_freed = shrink_free_pages(vb, pages_to_free);
-
- if (pages_freed >= pages_to_free)
- return pages_freed;
-
- pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
-
- return pages_freed;
+ return shrink_free_pages(vb, sc->nr_to_scan);
}

static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
@@ -839,26 +808,22 @@ static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
{
struct virtio_balloon *vb = container_of(shrinker,
struct virtio_balloon, shrinker);
- unsigned long count;
-
- count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
- count += vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;

- return count;
+ return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
}

-static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
+static int virtio_balloon_oom_notify(struct notifier_block *nb,
+ unsigned long dummy, void *parm)
{
- unregister_shrinker(&vb->shrinker);
-}
+ struct virtio_balloon *vb = container_of(nb,
+ struct virtio_balloon, oom_nb);
+ unsigned long *freed = parm;

-static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
-{
- vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
- vb->shrinker.count_objects = virtio_balloon_shrinker_count;
- vb->shrinker.seeks = DEFAULT_SEEKS;
+ *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
+ VIRTIO_BALLOON_PAGES_PER_PAGE;
+ update_balloon_size(vb);

- return register_shrinker(&vb->shrinker);
+ return NOTIFY_OK;
}

static int virtballoon_probe(struct virtio_device *vdev)
@@ -935,22 +900,35 @@ static int virtballoon_probe(struct virtio_device *vdev)
virtio_cwrite(vb->vdev, struct virtio_balloon_config,
poison_val, &poison_val);
}
- }
- /*
- * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
- * shrinker needs to be registered to relieve memory pressure.
- */
- if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
- err = virtio_balloon_register_shrinker(vb);
+
+ /*
+ * We're allowed to reuse any free pages, even if they are
+ * still to be processed by the host.
+ */
+ vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
+ vb->shrinker.count_objects = virtio_balloon_shrinker_count;
+ vb->shrinker.seeks = DEFAULT_SEEKS;
+ err = register_shrinker(&vb->shrinker);
if (err)
goto out_del_balloon_wq;
}
+ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
+ vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
+ vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
+ err = register_oom_notifier(&vb->oom_nb);
+ if (err < 0)
+ goto out_unregister_shrinker;
+ }
+
virtio_device_ready(vdev);

if (towards_target(vb))
virtballoon_changed(vdev);
return 0;

+out_unregister_shrinker:
+ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+ unregister_shrinker(&vb->shrinker);
out_del_balloon_wq:
if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
destroy_workqueue(vb->balloon_wq);
@@ -989,8 +967,11 @@ static void virtballoon_remove(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;

- if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
- virtio_balloon_unregister_shrinker(vb);
+ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+ unregister_oom_notifier(&vb->oom_nb);
+ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+ unregister_shrinker(&vb->shrinker);
+
spin_lock_irq(&vb->stop_update_lock);
vb->stop_update = true;
spin_unlock_irq(&vb->stop_update_lock);
--
2.25.1