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SubjectRe: [PATCH 5.6 086/126] virtio-balloon: Revert "virtio-balloon: Switch back to OOM handler for VIRTIO_BALLOON_F_DEFLATE_ON_OOM"
On Tue, May 26, 2020 at 08:53:43PM +0200, Greg Kroah-Hartman wrote:
> 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>

I don't understand. How does this make sense in stable?
stable does not merge akpm does it?

> ---
> 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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