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[2003:d8:2f4e:3200:c99d:a38b:3f3a:d4b3]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-427ea5b3acfsm20082945f8f.14.2025.10.21.05.59.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Oct 2025 05:59:42 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, Broadcom internal kernel review list , linux-doc@vger.kernel.org, virtualization@lists.linux.dev, David Hildenbrand , Andrew Morton , Oscar Salvador , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Arnd Bergmann , Greg Kroah-Hartman , Jerrin Shaji George , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Zi Yan Subject: [PATCH v1 05/23] mm/balloon_compaction: centralize adjust_managed_page_count() handling Date: Tue, 21 Oct 2025 14:59:10 +0200 Message-ID: <20251021125929.377194-6-david@redhat.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251021125929.377194-1-david@redhat.com> References: <20251021125929.377194-1-david@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: David Hildenbrand --- arch/powerpc/platforms/pseries/cmm.c | 13 +------------ drivers/virtio/virtio_balloon.c | 19 ++----------------- include/linux/balloon_compaction.h | 2 ++ mm/balloon_compaction.c | 17 +++++++++++++++++ 4 files changed, 22 insertions(+), 29 deletions(-) diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/= pseries/cmm.c index 07b21d2bc8a78..9ed71683ae402 100644 --- 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) =20 balloon_page_enqueue(&b_dev_info, page); atomic_long_inc(&loaned_pages); - adjust_managed_page_count(page, -1); nr--; } =20 @@ -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; } =20 - /* - * 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) !=3D 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; =20 balloon_devinfo_init(&b_dev_info); + b_dev_info.adjust_managed_page_count =3D true; if (IS_ENABLED(CONFIG_BALLOON_COMPACTION)) b_dev_info.migratepage =3D cmm_migratepage; =20 diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloo= n.c index 8969271581bca..f7d6a4a6e54f5 100644 --- 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) =20 set_page_pfns(vb, vb->pfns + vb->num_pfns, page); vb->num_pages +=3D 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 +=3D VIRTIO_BALLOON_PAGES_PER_PAGE; } =20 @@ -295,9 +292,6 @@ static void release_pages_balloon(struct virtio_balloon= *vb, struct page *page, *next; =20 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; =20 - /* - * 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) !=3D 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 =3D 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; =20 + if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) + vb->vb_dev_info.adjust_managed_page_count =3D true; #ifdef CONFIG_BALLOON_COMPACTION vb->vb_dev_info.migratepage =3D virtballoon_migratepage; #endif diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_com= paction.h index 7cfe48769239e..3109d3c43d306 100644 --- 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; }; =20 extern struct page *balloon_page_alloc(void); @@ -73,6 +74,7 @@ static inline void balloon_devinfo_init(struct balloon_de= v_info *balloon) spin_lock_init(&balloon->pages_lock); INIT_LIST_HEAD(&balloon->pages); balloon->migratepage =3D NULL; + balloon->adjust_managed_page_count =3D false; } =20 #ifdef CONFIG_BALLOON_COMPACTION diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c index 5444c61bb9e76..fd9ec47cf4670 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -23,6 +23,8 @@ static void balloon_page_enqueue_one(struct balloon_dev_i= nfo *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; =20 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); @@ -256,12 +260,25 @@ static int balloon_page_migrate(struct page *newpage,= struct page *page, =20 balloon_page_insert(b_dev_info, newpage); __count_vm_event(BALLOON_MIGRATE); + + if (b_dev_info->adjust_managed_page_count && + page_zone(page) !=3D 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); + } break; case -ENOENT: spin_lock_irqsave(&b_dev_info->pages_lock, flags); =20 /* 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); break; default: return rc; --=20 2.51.0