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[2003:d8:2f2c:5500:988:23f9:faa0:7232]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b471b9671asm2135708f8f.53.2025.07.04.03.26.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Jul 2025 03:26:46 -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 v2 28/29] mm/balloon_compaction: "movable_ops" doc updates Date: Fri, 4 Jul 2025 12:25:22 +0200 Message-ID: <20250704102524.326966-29-david@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250704102524.326966-1-david@redhat.com> References: <20250704102524.326966-1-david@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: pwq5sMM8W6qxYASe1TXgKC8tsRhEaNbVdS1iw1mo6cg_1751624808 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C472714000F X-Stat-Signature: 4ht1iqh3a5zrzayx6bgdq6ho7dgrbxtq X-HE-Tag: 1751624810-522875 X-HE-Meta: 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 dkhEXPOA 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Let's bring the docs up-to-date. Setting PG_movable_ops + page->private very likely still requires to be performed under documented locks: it's complicated. We will rework this in the future, as we will try avoiding using the page lock. Reviewed-by: Lorenzo Stoakes Signed-off-by: David Hildenbrand --- include/linux/balloon_compaction.h | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h index b222b0737c466..2fecfead91d26 100644 --- a/include/linux/balloon_compaction.h +++ b/include/linux/balloon_compaction.h @@ -4,12 +4,13 @@ * * Common interface definitions for making balloon pages movable by compaction. * - * Balloon page migration makes use of the general non-lru movable page + * Balloon page migration makes use of the general "movable_ops page migration" * feature. * * page->private is used to reference the responsible balloon device. - * page->mapping is used in context of non-lru page migration to reference - * the address space operations for page isolation/migration/compaction. + * That these pages have movable_ops, and which movable_ops apply, + * is derived from the page type (PageOffline()) combined with the + * PG_movable_ops flag (PageMovableOps()). * * As the page isolation scanning step a compaction thread does is a lockless * procedure (from a page standpoint), it might bring some racy situations while @@ -17,12 +18,10 @@ * and safely perform balloon's page compaction and migration we must, always, * ensure following these simple rules: * - * i. when updating a balloon's page ->mapping element, strictly do it under - * the following lock order, independently of the far superior - * locking scheme (lru_lock, balloon_lock): + * i. Setting the PG_movable_ops flag and page->private with the following + * lock order * +-page_lock(page); * +--spin_lock_irq(&b_dev_info->pages_lock); - * ... page->mapping updates here ... * * ii. isolation or dequeueing procedure must remove the page from balloon * device page list under b_dev_info->pages_lock. -- 2.49.0