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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Lance Yang , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Youngjun Park Subject: [PATCH] mm/huge_memory: Fix outdated comment about freeing subpages in __folio_split Date: Thu, 23 Apr 2026 11:49:17 +0800 Message-Id: <20260423034917.8234-1-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: x36j4q5bm4j9z6mzexgru8ngyusfoz66 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A063340003 X-HE-Tag: 1776916167-377448 X-HE-Meta: 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 AKgpIdCP 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The comment appears to be outdated. First, add_to_swap() no longer exists after Kairui’s commit b487a2da3575 ("mm, swap: simplify folio swap allocation"). Second, partially zapped folios are now always split before folio_alloc_swap() to avoid extra I/O, following Ryan’s commit 5ed890ce5147 ("mm: vmscan: avoid split during shrink_folio_list()"). Fix this by making the description more generic. Cc: David Hildenbrand Cc: Lorenzo Stoakes Cc: Zi Yan Cc: Baolin Wang Cc: "Liam R. Howlett" Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Lance Yang Cc: Chris Li Cc: Kairui Song Cc: Kemeng Shi Cc: Nhat Pham Cc: Baoquan He Cc: Youngjun Park Signed-off-by: Barry Song (Xiaomi) --- mm/huge_memory.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 970e077019b7..4586f3ccb133 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -4190,11 +4190,10 @@ static int __folio_split(struct folio *folio, unsigned int new_order, folio_unlock(new_folio); /* - * Subpages may be freed if there wasn't any mapping - * like if add_to_swap() is running on a lru page that - * had its mapping zapped. And freeing these pages - * requires taking the lru_lock so we do the put_page - * of the tail pages after the split is complete. + * Subpages whose mapping has been zapped may be freed + * earlier, but freeing them requires taking the + * lru_lock, so we defer put_page() on tail pages until + * after the split completes. */ free_folio_and_swap_cache(new_folio); } -- 2.39.3 (Apple Git-146)