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Subject[PATCH 5.6 086/126] virtio-balloon: Revert "virtio-balloon: Switch back to OOM handler for VIRTIO_BALLOON_F_DEFLATE_ON_OOM"
Date
From: Michael S. Tsirkin <mst@redhat.com>

[ Upstream commit 835a6a649d0dd1b1f46759eb60fff2f63ed253a7 ]

This reverts commit 5a6b4cc5b7a1892a8d7f63d6cbac6e0ae2a9d031.

It has been queued properly in the akpm tree, this version is just
creating conflicts.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/virtio/virtio_balloon.c | 107 +++++++++++++++++++-------------
1 file changed, 63 insertions(+), 44 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 44375a22307b..341458fd95ca 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -14,7 +14,6 @@
#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>
@@ -28,9 +27,7 @@
*/
#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
-/* 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 VIRTBALLOON_OOM_NOTIFY_PRIORITY 80

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

- /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
+ /* To register a shrinker to shrink memory upon memory pressure */
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[] = {
@@ -794,13 +788,50 @@ 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);

- return shrink_free_pages(vb, sc->nr_to_scan);
+ 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;
}

static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
@@ -808,22 +839,26 @@ 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 vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
+ return count;
}

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

- *freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
- VIRTIO_BALLOON_PAGES_PER_PAGE;
- update_balloon_size(vb);
+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;

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

static int virtballoon_probe(struct virtio_device *vdev)
@@ -900,35 +935,22 @@ static int virtballoon_probe(struct virtio_device *vdev)
virtio_cwrite(vb->vdev, struct virtio_balloon_config,
poison_val, &poison_val);
}
-
- /*
- * 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);
+ }
+ /*
+ * 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);
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);
@@ -967,11 +989,8 @@ static void virtballoon_remove(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;

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


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