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charset=UTF-8 Date: Mon, 10 Aug 2026 20:20:50 +0800 X-Mailer: git-send-email 2.45.2 To: , , , , , , , , , , , Cc: , , , , , X-Lms-Return-Path: X-Original-From: Li Zhe Message-Id: <20260810122057.30447-2-lizhe.67@bytedance.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit In-Reply-To: <20260810122057.30447-1-lizhe.67@bytedance.com> References: <20260810122057.30447-1-lizhe.67@bytedance.com> From: "Li Zhe" Subject: [PATCH v10 1/8] mm: fix stale ZONE_DEVICE refcount comment X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: hyttj7bmoj1n5ddm5ewk1e8kyppe38a7 X-Rspamd-Queue-Id: 116B8120002 X-HE-Tag: 1786364528-768428 X-HE-Meta: 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 blVSIbz9 R73AaO5fMPMB0enbP65BBF/4tbg86AyZXkUb/ddGwm3BDK/aAu8UoYmOwA+voakBDiDYJ11GruOqKvxQVRC9A7gAwyaPL/uWkdrGWU3oTDQIBYYDPX11H8Dp/EW01kQEWfgHF3TlovSNIS8lXcXdEVRS3aNBLTFnqHGX6GRpIVHQIqGtFjeGp6yK/6N4BMKbkWo28fywDKjv5pdXiWzU35omTSDcB5yog02wSqZC7+IOGBS9z9c1nlaRnfKQv69Af3qq6IOU0EPKqHAXlrJkR+Q8T+RGrthI//Nl83DCnrXHHkiKhUL09vGQC10DYXr0k1Oerm3793vUrP2Tt/d0hucS+HUMfWLPRSr8wtww/XBcpfye2YXpZOGzSlvQKkhotIwgn+WejNJZLrySbaXyG2JMJgQA7dPIdAEHpRtR7S+68t/l42H9hjDJDkVLlJFy6TpV6+mw6OdD+x1B77ERsUCtlUQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The comment in __init_zone_device_page() still uses the old MEMORY_TYPE_* names and implies that FS_DAX pages regain a refcount of 1 in the free path. That no longer matches the code. Update the comment to describe the current policy correctly: MEMORY_DEVICE_GENERIC pages regain a refcount of 1 in the free path, while the remaining ZONE_DEVICE types start from 0 here and raise the count again when the allocator or driver hands the page out. No functional change intended. Signed-off-by: Li Zhe Reviewed-by: David Hildenbrand (Arm) Reviewed-by: Alistair Popple Reviewed-by: Muchun Song --- mm/mm_init.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/mm/mm_init.c b/mm/mm_init.c index 0f64909e8d20..95808ab5cfdb 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -1030,13 +1030,9 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn, page->zone_device_data = NULL; /* - * ZONE_DEVICE pages other than MEMORY_TYPE_GENERIC are released - * directly to the driver page allocator which will set the page count - * to 1 when allocating the page. - * - * MEMORY_TYPE_GENERIC and MEMORY_TYPE_FS_DAX pages automatically have - * their refcount reset to one whenever they are freed (ie. after - * their refcount drops to 0). + * MEMORY_DEVICE_GENERIC pages regain a refcount of 1 in the free + * path. The remaining ZONE_DEVICE types start from 0 here and raise + * the count again when the allocator or driver hands the page out. */ switch (pgmap->type) { case MEMORY_DEVICE_FS_DAX: -- 2.20.1