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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782197567; 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=GvIJsA3YqPuqH4YFKYfsJHGBnY+wCnYdbztz69l5314=; b=Eek4DDfgEZSCdU9HKwxGDYhui2nzE/cv3JiXat1CNGLY2dRdLYYhUNyW5uTJ2Sy3qQ2kSH WezQAHINUaEa48AdA2V0u6Zt5VgVBxyoN5nMs05fZNSFE4tM2Z6ueR7MlV0jVqtWn3v3c3 1fmhRdzeYn4Hbmrg93Dg0i10MmyllKQ= From: Ye Liu To: Andrew Morton , Vlastimil Babka Cc: Ye Liu , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/6] mm/page_owner: extract skip_buddy_pages() helper to unify buddy page skipping Date: Tue, 23 Jun 2026 14:52:26 +0800 Message-ID: <20260623065234.31866-2-ye.liu@linux.dev> In-Reply-To: <20260623065234.31866-1-ye.liu@linux.dev> References: <20260623065234.31866-1-ye.liu@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E493180008 X-Stat-Signature: cq6j8at5i147ys8xqieicumkuyiwbd1p X-HE-Tag: 1782197569-731283 X-HE-Meta: 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 e31kGHZP kgXLhLBdqcZkmm1TAFF8T3qmn0ZmMuEAZmCbNp7zipeeQin/Aske/Qsuc8d4NF8DVjqN+6aqY2gV0fk/QiIw8uAHtiALDbd43VRyi/DTKHDQqWEEaiWh4WYlZdyuBmzjIlcHfDdOYaxDTRJdcIs0PalqYwraKJQy7cb+G9f00MZN0X86AGTJlPT5RbWkBjOJ3gcE5O4FLRYWIUl1+cX8tkLHuL92ovFcVQ41Ar79HoTFM42YfkZVstefg1A== 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 --- 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