From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta0.migadu.com (out-181.mta0.migadu.com [91.218.175.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 24B7F23EAB2 for ; Fri, 26 Jun 2026 02:46:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782441968; cv=none; b=XcViiXIIXac0G4EJ+/HDCYr/eimQzrdzdF9Ss3Sg/dCIYmF8Kyox9oI2/PbsRawYgohgh/AS8/LhVJkranv9PM8qpIK896Drh6vRkJfrz310O5yGo4nDpEjQrJSoPRvNX0T9jpPHLAP2ptU7KmTQU3rMbcPyFH1cDMkg47C+ofY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782441968; c=relaxed/simple; bh=HjBwuxbLvXAFAG1t1ufzq0MGnwLRzlIQNkCIjAGhI3k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RVOSZPkzjrwvzJVTrYnIF2IrdEynaYNLeQqiZHRDczZUCc12BOkkBBkIE1l05l9uvO7rbnH9B0E2ZAfZ4kIs2rF4ZB0mgdHLuuBofMCn/dGGHgz2tJJPEjTXGGIbNa2Gk3/ZH1yrpnfNGxqRyW7Of304Q8Zg28jHSudkz0yR8YY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=gGoT6wNJ; arc=none smtp.client-ip=91.218.175.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="gGoT6wNJ" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1782441964; 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=gGoT6wNJnWEEuS0KISWu6vpmFckqv8DVGTIepePx/OSA9YQav0Y7gHwOp5YMxrsJ9aJywa hlaZNPMdBNGC8Y9bOyx2YMseA3Ffk95gmnP/tCDZdzXktnGRGWFyyQW0Fd1J22gQzXOe+5 RsxpH2Z4luSnWc73dc8F4sTXNJIArIg= 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 v2 1/6] mm/page_owner: extract skip_buddy_pages() helper to unify buddy page skipping Date: Fri, 26 Jun 2026 10:45:40 +0800 Message-ID: <20260626024550.25677-2-ye.liu@linux.dev> In-Reply-To: <20260626024550.25677-1-ye.liu@linux.dev> References: <20260626024550.25677-1-ye.liu@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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