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[2003:d8:2f2d:2400:4052:3b5:fff9:4ed0]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-4535ebcecdcsm3339075e9.36.2025.06.18.10.40.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Jun 2025 10:40:21 -0700 (PDT) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org, David Hildenbrand , Andrew Morton , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Jerrin Shaji George , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , Alexander Viro , Christian Brauner , Jan Kara , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Minchan Kim , Sergey Senozhatsky , Brendan Jackman , Johannes Weiner , Jason Gunthorpe , John Hubbard , Peter Xu , Xu Xin , Chengming Zhou , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , Rik van Riel , Harry Yoo , Qi Zheng , Shakeel Butt Subject: [PATCH RFC 02/29] mm/balloon_compaction: convert balloon_page_delete() to balloon_page_finalize() Date: Wed, 18 Jun 2025 19:39:45 +0200 Message-ID: <20250618174014.1168640-3-david@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250618174014.1168640-1-david@redhat.com> References: <20250618174014.1168640-1-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 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. 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. Signed-off-by: David Hildenbrand --- 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 5f4037c1d7fe8..5e0a718d1be7b 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_d= ev_info, =20 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); =20 @@ -542,6 +541,7 @@ static int cmm_migratepage(struct balloon_dev_info *b_d= ev_info, */ plpar_page_set_active(page); =20 + balloon_page_finalize(page); /* balloon page list reference */ put_page(page); =20 diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c index c817d8c216413..6653fc53c951c 100644 --- a/drivers/misc/vmw_balloon.c +++ b/drivers/misc/vmw_balloon.c @@ -1778,8 +1778,7 @@ static int vmballoon_migratepage(struct balloon_dev_i= nfo *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); =20 /* Inflate */ diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloo= n.c index 89da052f4f687..e299e18346a30 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); =20 /* 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 =3D VIRTIO_BALLOON_PAGES_PER_PAGE; set_page_pfns(vb, vb->pfns, page); tell_host(vb, vb->deflate_vq); =20 mutex_unlock(&vb->balloon_lock); =20 + balloon_page_finalize(page); put_page(page); /* balloon reference */ =20 return MIGRATEPAGE_SUCCESS; diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_com= paction.h index 5ca2d56996201..b9f19da37b089 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_de= v_info *balloon, list_add(&page->lru, &balloon->pages); } =20 -/* - * 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 ball= oon - * 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 dev= ice * 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); } =20 -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) =20 #endif /* CONFIG_BALLOON_COMPACTION */ =20 +/* + * 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 fcb60233aa35d..ec176bdb8a78b 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -94,7 +94,8 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info = *b_dev_info, if (!trylock_page(page)) continue; =20 - 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); --=20 2.49.0