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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 v3 04/24] mm/balloon_compaction: improve comments for WARN_ON_ONCE(!b_dev_info) Date: Tue, 20 Jan 2026 00:01:12 +0100 Message-ID: <20260119230133.3551867-5-david@kernel.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260119230133.3551867-1-david@kernel.org> References: <20260119230133.3551867-1-david@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 91DB3C000D X-Stat-Signature: up8cq8si8a81prsc7ap96fpmdrd7ieot X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1768863730-526738 X-HE-Meta: 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 AkJeUjpp YF+9bBSwKM7QfhK/7M+h3GSlAHa+iFHco3m8udCGn56oNY1F4ovR+v7HGSoc5ZCxBbwqdcbcj3zzsK2ou2RPdz8wXO0ZepB4mmm46j8NH69uIBGSXTmWxVMi9XfS4/QKjm+CsU4Nayw6eDiHokhC0aFCfBHxDD2a8tSmBMDJxiD9K0tUm+i6/12bZt43y4UcgouK8VTSepG6UFDEO5U9H+yv8yI+x+ZOI7YCJ4M0qqPlycTBwC2eUI5dccXWUUDYQaxKRsxaQkCJvv4tQYQalC03bipk4vxRRgplj 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 clarify a bit by extending the comments. Signed-off-by: David Hildenbrand (Red Hat) --- mm/balloon_compaction.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c index 03c5dbabb1565..85eea88cea083 100644 --- a/mm/balloon_compaction.c +++ b/mm/balloon_compaction.c @@ -222,7 +222,11 @@ static void balloon_page_putback(struct page *page) struct balloon_dev_info *b_dev_info = balloon_page_device(page); unsigned long flags; - /* Isolated balloon pages cannot get deflated. */ + /* + * When we isolated the page, the page was still inflated in a balloon + * device. As isolated balloon pages cannot get deflated, we still have + * a balloon device here. + */ if (WARN_ON_ONCE(!b_dev_info)) return; @@ -241,7 +245,11 @@ static int balloon_page_migrate(struct page *newpage, struct page *page, VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageLocked(newpage), newpage); - /* Isolated balloon pages cannot get deflated. */ + /* + * When we isolated the page, the page was still inflated in a balloon + * device. As isolated balloon pages cannot get deflated, we still have + * a balloon device here. + */ if (WARN_ON_ONCE(!balloon)) return -EAGAIN; -- 2.52.0