mm/balloon_compaction: convert balloon_page_delete() to balloon_page_finalize()

[ 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c
index 6b38ccd63c90888310baed1d8ae13135fc850654..d54d599be8b37080fa52b48e1cef4833dacff95a 100644 (file)
--- a/arch/powerpc/platforms/pseries/cmm.c
+++ b/arch/powerpc/platforms/pseries/cmm.c
@@ -550,7 +550,6 @@ 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);
 
@@ -560,6 +559,7 @@ 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 b837e7eba5f7dcec2ae1f15bb2052c18b9a0f306..be1004a3166468ba64fbf715040f53b9f1b99112 100644 (file)
--- a/drivers/misc/vmw_balloon.c
+++ b/drivers/misc/vmw_balloon.c
@@ -1810,8 +1810,7 @@ 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 935ea2f3dac7dba1d916a3899df6b7fe4dc42e81..98e9d77911bc5bae648ecb41aca83ce5be2e27a3 100644 (file)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -796,15 +796,13 @@ 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 edb7f6d41faa043d0a59b80eb0ba30307dea8fdf..ee30fb134478368b81e9bdd1249b4bdf7fc98e9d 100644 (file)
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h
@@ -99,27 +99,6 @@ 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.
@@ -143,12 +122,6 @@ 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;
@@ -156,6 +129,22 @@ 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 02bcc22a6e77a3037f1fce5fc61ed5659d66c473..c187b708477b0e8216c84364dc56fa29eaae2f92 100644 (file)
--- 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);