mm/balloon_compaction: centralize adjust_managed_page_count() handling

Let's centralize it, by allowing for the driver to enable this handling
through a new flag (bool for now) in the balloon device info.

Note that we now adjust the counter when adding/removing a page into the
balloon list: when removing a page to deflate it, it will now happen
before the driver communicated with hypervisor, not afterwards.

This shouldn't make a difference in practice.

Link: https://lkml.kernel.org/r/20260119230133.3551867-7-david@kernel.org
Signed-off-by: David Hildenbrand (Red Hat) <david@kernel.org>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Eugenio Pérez <eperezma@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jerrin Shaji George <jerrin.shaji-george@broadcom.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c
index 15f873f733a41849812fba22f44a4bf9dcfdd25a..7fd8b3d7e7637204e5e7375845c12d44c4e7411a 100644 (file)
--- a/arch/powerpc/platforms/pseries/cmm.c
+++ b/arch/powerpc/platforms/pseries/cmm.c
@@ -165,7 +165,6 @@ static long cmm_alloc_pages(long nr)
 
                balloon_page_enqueue(&b_dev_info, page);
                atomic_long_inc(&loaned_pages);
-               adjust_managed_page_count(page, -1);
                nr--;
        }
 
@@ -190,7 +189,6 @@ static long cmm_free_pages(long nr)
                if (!page)
                        break;
                plpar_page_set_active(page);
-               adjust_managed_page_count(page, 1);
                __free_page(page);
                atomic_long_dec(&loaned_pages);
                nr--;
@@ -515,16 +513,6 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
                return -EBUSY;
        }
 
-       /*
-        * When we migrate a page to a different zone, we have to fixup the
-        * count of both involved zones as we adjusted the managed page count
-        * when inflating.
-        */
-       if (page_zone(page) != page_zone(newpage)) {
-               adjust_managed_page_count(page, 1);
-               adjust_managed_page_count(newpage, -1);
-       }
-
        /*
         * activate/"deflate" the old page. We ignore any errors just like the
         * other callers.
@@ -551,6 +539,7 @@ static int cmm_init(void)
                return -EOPNOTSUPP;
 
        balloon_devinfo_init(&b_dev_info);
+       b_dev_info.adjust_managed_page_count = true;
        if (IS_ENABLED(CONFIG_BALLOON_COMPACTION))
                b_dev_info.migratepage = cmm_migratepage;
 

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index df2756c071dae4faa1f67a5e79fd6dc5748b3554..15c1cf5fd249c682ab3a4c975cfb2afc0dee60ee 100644 (file)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -274,9 +274,6 @@ static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
 
                set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
                vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
-               if (!virtio_has_feature(vb->vdev,
-                                       VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
-                       adjust_managed_page_count(page, -1);
                vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
        }
 
@@ -295,9 +292,6 @@ static void release_pages_balloon(struct virtio_balloon *vb,
        struct page *page, *next;
 
        list_for_each_entry_safe(page, next, pages, lru) {
-               if (!virtio_has_feature(vb->vdev,
-                                       VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
-                       adjust_managed_page_count(page, 1);
                list_del(&page->lru);
                put_page(page); /* balloon reference */
        }
@@ -839,17 +833,6 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
        if (!mutex_trylock(&vb->balloon_lock))
                return -EAGAIN;
 
-       /*
-         * When we migrate a page to a different zone and adjusted the
-         * managed page count when inflating, we have to fixup the count of
-         * both involved zones.
-         */
-       if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
-           page_zone(page) != page_zone(newpage)) {
-               adjust_managed_page_count(page, 1);
-               adjust_managed_page_count(newpage, -1);
-       }
-
        /* balloon's page migration 1st step  -- inflate "newpage" */
        vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
        set_page_pfns(vb, vb->pfns, newpage);
@@ -958,6 +941,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
        if (err)
                goto out_free_vb;
 
+       if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+               vb->vb_dev_info.adjust_managed_page_count = true;
 #ifdef CONFIG_BALLOON_COMPACTION
        vb->vb_dev_info.migratepage = virtballoon_migratepage;
 #endif

diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index 7cfe48769239e6b1c983f711a0bdfdda150d24a2..3109d3c43d3065bebe6fdee28cb3a35bc2594b99 100644 (file)
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -56,6 +56,7 @@ struct balloon_dev_info {
        struct list_head pages;         /* Pages enqueued & handled to Host */
        int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
                        struct page *page, enum migrate_mode mode);
+       bool adjust_managed_page_count;
 };
 
 extern struct page *balloon_page_alloc(void);
@@ -73,6 +74,7 @@ static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
        spin_lock_init(&balloon->pages_lock);
        INIT_LIST_HEAD(&balloon->pages);
        balloon->migratepage = NULL;
+       balloon->adjust_managed_page_count = false;
 }
 
 #ifdef CONFIG_BALLOON_COMPACTION

diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
index 764fa25dc4bd155d0a4ebd67be30f7e2fe2a61cd..4fe2a0cff69ec3b65525dfa12f51a1f76ce556a9 100644 (file)
--- a/mm/balloon_compaction.c
+++ b/mm/balloon_compaction.c
@@ -23,6 +23,8 @@ static void balloon_page_enqueue_one(struct balloon_dev_info *b_dev_info,
        BUG_ON(!trylock_page(page));
        balloon_page_insert(b_dev_info, page);
        unlock_page(page);
+       if (b_dev_info->adjust_managed_page_count)
+               adjust_managed_page_count(page, -1);
        __count_vm_event(BALLOON_INFLATE);
        inc_node_page_state(page, NR_BALLOON_PAGES);
 }
@@ -95,6 +97,8 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info,
                        continue;
 
                list_del(&page->lru);
+               if (b_dev_info->adjust_managed_page_count)
+                       adjust_managed_page_count(page, 1);
                balloon_page_finalize(page);
                __count_vm_event(BALLOON_DEFLATE);
                list_add(&page->lru, pages);
@@ -264,9 +268,22 @@ static int balloon_page_migrate(struct page *newpage, struct page *page,
                get_page(newpage);
                balloon_page_insert(b_dev_info, newpage);
                __count_vm_event(BALLOON_MIGRATE);
+
+               if (b_dev_info->adjust_managed_page_count &&
+                   page_zone(page) != page_zone(newpage)) {
+                       /*
+                        * When we migrate a page to a different zone we
+                        * have to fixup the count of both involved zones.
+                        */
+                       adjust_managed_page_count(page, 1);
+                       adjust_managed_page_count(newpage, -1);
+               }
        } else {
                /* Old page was deflated but new page not inflated. */
                __count_vm_event(BALLOON_DEFLATE);
+
+               if (b_dev_info->adjust_managed_page_count)
+                       adjust_managed_page_count(page, 1);
        }
 
        b_dev_info->isolated_pages--;