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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782868973; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JMExFnjyQtVXN7x+iPdJHV2C/UohwacNGTdpQ/luPkA=; b=SyYEUTYWxEfXkpe6axwG2eg4sc2sFHN9VJs/m2VpqmEWmnnUhsv2kg9xuNZQME1zhILi5s 1CLpml0Qek4So6jIAJjtLTh7GpXpzW7+9eypDyYYABkmB3D0TWWO7IDBQn1pzDy9OJd+lB baGnRGtdpeum6k3IRxUxCbOkOVeb13U= From: Ye Liu To: Andrew Morton , Vlastimil Babka Cc: Ye Liu , Zi Yan , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 1/7] mm/page_owner: extract skip_buddy_pages() helper to unify buddy page skipping Date: Wed, 1 Jul 2026 09:22:27 +0800 Message-ID: <20260701012239.315262-2-ye.liu@linux.dev> In-Reply-To: <20260701012239.315262-1-ye.liu@linux.dev> References: <20260701012239.315262-1-ye.liu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6E0A940008 X-Stat-Signature: z9i5rxtmhpi7jysshqt6w396iphfd5ct X-HE-Tag: 1782868974-100511 X-HE-Meta: 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 BaR3b2Jk qc+wvOPQDPGDHipjPXaXnk0+fkI3AXZ6RPBiqWyvdZ/sc/+lYovkRX/iJ8FbDP/hbxjryptCuRoAPl7z17WPFwQYe9UvrAQAd8JMKIu0QHLQ/A5Jlfitl/dnRZDk0NX2JqpzinHvi2A+H+e+vcHxaSbPcemIi7KxWab8gnFqmd9XElObBp643NLtSBqiMH8DAS4UABgAKpmHsZLJWqJOXPg4yFWWalNA9A80GG/ekJbUGULbHBheAPr9B5bPlczhLzKBfN54Nfmo2Ro+sYhG2awrBGhGWfuwcW3TAEFz4KjEgccg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Three places in page_owner.c duplicate the same pattern: check if a page is PageBuddy, read its order via buddy_order_unsafe(), advance the pfn past the buddy block if the order is valid, and continue. Consolidate them into a single inline helper skip_buddy_pages(). The function returns true (skip) for any buddy page and advances @pfn past the block when the order is valid; returns false if the page is not a buddy page and should be processed normally. The old init_pages_in_zone() variant used "order > 0" as an extra guard before advancing pfn, but the continue was unconditional and (1UL << 0) - 1 == 0, so the behaviour is identical. The comment about zone->lock is preserved in the helper's kernel-doc. No functional change. Signed-off-by: Ye Liu Reviewed-by: Zi Yan Reviewed-by: Vlastimil Babka (SUSE) --- mm/page_owner.c | 52 ++++++++++++++++++++++++------------------------- 1 file changed, 26 insertions(+), 26 deletions(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index 2dddcb6510aa..342549891a8d 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -422,6 +422,29 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old) rcu_read_unlock(); } +/* + * Check if a page is a buddy page and advance @pfn past the entire buddy block. + * This safely reads the buddy order without the zone lock, which may cause us + * to skip less than the full buddy block, but that is acceptable for page owner + * iteration purposes. + * + * Return: true if the page was skipped (caller should continue its loop), + * false if the page is not a buddy page and should be processed normally. + */ +static inline bool skip_buddy_pages(unsigned long *pfn, struct page *page) +{ + unsigned long order; + + if (!PageBuddy(page)) + return false; + + order = buddy_order_unsafe(page); + if (order <= MAX_PAGE_ORDER) + *pfn += (1UL << order) - 1; + + return true; +} + void pagetypeinfo_showmixedcount_print(struct seq_file *m, pg_data_t *pgdat, struct zone *zone) { @@ -461,14 +484,8 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m, if (page_zone(page) != zone) continue; - if (PageBuddy(page)) { - unsigned long freepage_order; - - freepage_order = buddy_order_unsafe(page); - if (freepage_order <= MAX_PAGE_ORDER) - pfn += (1UL << freepage_order) - 1; + if (skip_buddy_pages(&pfn, page)) continue; - } if (PageReserved(page)) continue; @@ -697,13 +714,8 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) } page = pfn_to_page(pfn); - if (PageBuddy(page)) { - unsigned long freepage_order = buddy_order_unsafe(page); - - if (freepage_order <= MAX_PAGE_ORDER) - pfn += (1UL << freepage_order) - 1; + if (skip_buddy_pages(&pfn, page)) continue; - } page_ext = page_ext_get(page); if (unlikely(!page_ext)) @@ -798,20 +810,8 @@ static void init_pages_in_zone(struct zone *zone) if (page_zone(page) != zone) continue; - /* - * To avoid having to grab zone->lock, be a little - * careful when reading buddy page order. The only - * danger is that we skip too much and potentially miss - * some early allocated pages, which is better than - * heavy lock contention. - */ - if (PageBuddy(page)) { - unsigned long order = buddy_order_unsafe(page); - - if (order > 0 && order <= MAX_PAGE_ORDER) - pfn += (1UL << order) - 1; + if (skip_buddy_pages(&pfn, page)) continue; - } if (PageReserved(page)) continue; -- 2.43.0