From: David Hildenbrand david@redhat.com

[ Upstream commit 15504b1163007bbfbd9a63460d5c14737c16e96d ]

Let's move the removal of the page from the balloon list into the single caller, to remove the dependency on the PG_isolated flag and clarify locking requirements.

Note that for now, balloon_page_delete() was used on two paths:

(1) Removing a page from the balloon for deflation through balloon_page_list_dequeue() (2) Removing an isolated page from the balloon for migration in the per-driver migration handlers. Isolated pages were already removed from the balloon list during isolation.

So instead of relying on the flag, we can just distinguish both cases directly and handle it accordingly in the caller.

We'll shuffle the operations a bit such that they logically make more sense (e.g., remove from the list before clearing flags).

In balloon migration functions we can now move the balloon_page_finalize() out of the balloon lock and perform the finalization just before dropping the balloon reference.

Document that the page lock is currently required when modifying the movability aspects of a page; hopefully we can soon decouple this from the page lock.

Link: https://lkml.kernel.org/r/20250704102524.326966-3-david@redhat.com Signed-off-by: David Hildenbrand david@redhat.com Reviewed-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com Cc: Alistair Popple apopple@nvidia.com Cc: Al Viro viro@zeniv.linux.org.uk Cc: Arnd Bergmann arnd@arndb.de Cc: Brendan Jackman jackmanb@google.com Cc: Byungchul Park byungchul@sk.com Cc: Chengming Zhou chengming.zhou@linux.dev Cc: Christian Brauner brauner@kernel.org Cc: Christophe Leroy christophe.leroy@csgroup.eu Cc: Eugenio Pé rez eperezma@redhat.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Gregory Price gourry@gourry.net Cc: Harry Yoo harry.yoo@oracle.com Cc: "Huang, Ying" ying.huang@linux.alibaba.com Cc: Jan Kara jack@suse.cz Cc: Jason Gunthorpe jgg@ziepe.ca Cc: Jason Wang jasowang@redhat.com Cc: Jerrin Shaji George jerrin.shaji-george@broadcom.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: John Hubbard jhubbard@nvidia.com Cc: Jonathan Corbet corbet@lwn.net Cc: Joshua Hahn joshua.hahnjy@gmail.com Cc: Liam Howlett liam.howlett@oracle.com Cc: Madhavan Srinivasan maddy@linux.ibm.com Cc: Mathew Brost matthew.brost@intel.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Miaohe Lin linmiaohe@huawei.com Cc: Michael Ellerman mpe@ellerman.id.au Cc: "Michael S. Tsirkin" mst@redhat.com Cc: Michal Hocko mhocko@suse.com Cc: Mike Rapoport rppt@kernel.org Cc: Minchan Kim minchan@kernel.org Cc: Naoya Horiguchi nao.horiguchi@gmail.com Cc: Nicholas Piggin npiggin@gmail.com Cc: Oscar Salvador osalvador@suse.de Cc: Peter Xu peterx@redhat.com Cc: Qi Zheng zhengqi.arch@bytedance.com Cc: Rakie Kim rakie.kim@sk.com Cc: Rik van Riel riel@surriel.com Cc: Sergey Senozhatsky senozhatsky@chromium.org Cc: Shakeel Butt shakeel.butt@linux.dev Cc: Suren Baghdasaryan surenb@google.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Xuan Zhuo xuanzhuo@linux.alibaba.com Cc: xu xin xu.xin16@zte.com.cn Cc: Zi Yan ziy@nvidia.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Stable-dep-of: 0da2ba35c0d5 ("powerpc/pseries/cmm: adjust BALLOON_MIGRATE when migrating pages") Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/platforms/pseries/cmm.c | 2 +- drivers/misc/vmw_balloon.c | 3 +- drivers/virtio/virtio_balloon.c | 4 +-- include/linux/balloon_compaction.h | 43 +++++++++++----------------- mm/balloon_compaction.c | 3 +- 5 files changed, 21 insertions(+), 34 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c index 5f4037c1d7fe..5e0a718d1be7 100644 --- a/arch/powerpc/platforms/pseries/cmm.c +++ b/arch/powerpc/platforms/pseries/cmm.c @@ -532,7 +532,6 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,

spin_lock_irqsave(&b_dev_info->pages_lock, flags); balloon_page_insert(b_dev_info, newpage); - balloon_page_delete(page); b_dev_info->isolated_pages--; spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);

@@ -542,6 +541,7 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info, */ plpar_page_set_active(page);

+ balloon_page_finalize(page); /* balloon page list reference */ put_page(page);

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c index c817d8c21641..6653fc53c951 100644 --- a/drivers/misc/vmw_balloon.c +++ b/drivers/misc/vmw_balloon.c @@ -1778,8 +1778,7 @@ static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info, * @pages_lock . We keep holding @comm_lock since we will need it in a * second. */ - balloon_page_delete(page); - + balloon_page_finalize(page); put_page(page);

/* Inflate */ diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index b36d2803674e..b7b9fb80d6a0 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -866,15 +866,13 @@ static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info, tell_host(vb, vb->inflate_vq);

/* balloon's page migration 2nd step -- deflate "page" */ - spin_lock_irqsave(&vb_dev_info->pages_lock, flags); - balloon_page_delete(page); - spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags); vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE; set_page_pfns(vb, vb->pfns, page); tell_host(vb, vb->deflate_vq);

mutex_unlock(&vb->balloon_lock);

+ balloon_page_finalize(page); put_page(page); /* balloon reference */

return MIGRATEPAGE_SUCCESS; diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h index 5ca2d5699620..b9f19da37b08 100644 --- a/include/linux/balloon_compaction.h +++ b/include/linux/balloon_compaction.h @@ -97,27 +97,6 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon, list_add(&page->lru, &balloon->pages); }

-/* - * balloon_page_delete - delete a page from balloon's page list and clear - * the page->private assignement accordingly. - * @page : page to be released from balloon's page list - * - * Caller must ensure the page is locked and the spin_lock protecting balloon - * pages list is held before deleting a page from the balloon device. - */ -static inline void balloon_page_delete(struct page *page) -{ - __ClearPageOffline(page); - __ClearPageMovable(page); - set_page_private(page, 0); - /* - * No touch page.lru field once @page has been isolated - * because VM is using the field. - */ - if (!PageIsolated(page)) - list_del(&page->lru); -} - /* * balloon_page_device - get the b_dev_info descriptor for the balloon device * that enqueues the given page. @@ -141,12 +120,6 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon, list_add(&page->lru, &balloon->pages); }

-static inline void balloon_page_delete(struct page *page) -{ - __ClearPageOffline(page); - list_del(&page->lru); -} - static inline gfp_t balloon_mapping_gfp_mask(void) { return GFP_HIGHUSER; @@ -154,6 +127,22 @@ static inline gfp_t balloon_mapping_gfp_mask(void)

#endif /* CONFIG_BALLOON_COMPACTION */

+/* + * balloon_page_finalize - prepare a balloon page that was removed from the + * balloon list for release to the page allocator + * @page: page to be released to the page allocator + * + * Caller must ensure that the page is locked. + */ +static inline void balloon_page_finalize(struct page *page) +{ + if (IS_ENABLED(CONFIG_BALLOON_COMPACTION)) { + __ClearPageMovable(page); + set_page_private(page, 0); + } + __ClearPageOffline(page); +} + /* * balloon_page_push - insert a page into a page list. * @head : pointer to list diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c index 387786b34c3b..009704f257f1 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -93,7 +93,8 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, if (!trylock_page(page)) continue;

- balloon_page_delete(page); + list_del(&page->lru); + balloon_page_finalize(page); __count_vm_event(BALLOON_DEFLATE); list_add(&page->lru, pages); unlock_page(page);