From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-172.mta1.migadu.com (out-172.mta1.migadu.com [95.215.58.172]) (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 14DBE322768 for ; Mon, 27 Jul 2026 14:05:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785161162; cv=none; b=Npse/KCphis/NM9nyN+BaSEUMHqJPnvCX94r+b3q0C0rvkEfJmNCgrUc1y9dmSXYrV4wV5Yd2eNoF/MehYrwD/r6CeqrtM6Mv/21a/buvZK1r15NoYNyxOelW/SfCtfdhTVKcUC6Ojd5fwHmcrhCJoEtrrR9sf1EjcVEpj8Xpbo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785161162; c=relaxed/simple; bh=93znEjNI2Y/aZDVuZRJ7jffMxgACntVFuyf7/GYdHj4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type:Content-type; b=EmQeBrFlw+7mbchmMVtJfgZIglzuvyOreuxPg//vvsUnT5QQ7gx1r3svupJO0ic+MTw7VH0NKqcb9ZV4iFO971SHhxC3DaRu5b4HOu4ikxbhi2w6QubTRDw/P5C4eQKnAQBw1L0xtGeAQSEW9uw1qvnM7QCULX4GPVUa3oY6kTk= 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=gzl4GgGR; arc=none smtp.client-ip=95.215.58.172 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="gzl4GgGR" 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=1785161156; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YIy7Qx8bWx3spNRm9c+a9lBeger9sWyHhg8HX/HO6dc=; b=gzl4GgGR4lMlT4GFvFX0H4fZvvSa2NxagVAz1kmeIT9am0LuT7+OuZjYu3dudnRZvFhOky AAXBCpsw1zqmvShsQCx76V1b5GncmImu0UdfcGWXCAA9GT6PdytI6yEHWCYGVore2Fxhf4 heog055s99I5etWPF+qIlajFLDAtnPM= From: Baoquan He To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, chrisl@kernel.org, nphamcs@gmail.com, kasong@tencent.com, baohua@kernel.org, youngjun.park@lge.com, hannes@cmpxchg.org, yosry@kernel.org, david@kernel.org, shikemeng@huaweicloud.com, chengming.zhou@linux.dev, linux-kernel@vger.kernel.org, Baoquan He Subject: [RFC PATCH 06/11] mm, swap: free backing pages in xswap_unmap_clusters Date: Mon, 27 Jul 2026 22:04:57 +0800 Message-ID: <20260727140503.1060918-5-baoquan.he@linux.dev> In-Reply-To: <20260727140503.1060918-1-baoquan.he@linux.dev> References: <20260727135029.1059441-1-baoquan.he@linux.dev> <20260727140503.1060918-1-baoquan.he@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT vm_area_unmap_pages() only clears PTEs and frees intermediate page table pages — it does not free the backing physical pages allocated by xswap_map_clusters(). Fix this by walking the page table with apply_to_existing_page_range() before the unmap to collect all struct pages in the range. After vunmap_range() clears the PTEs, free the collected pages via __free_page(). Use a simple xswap_page_data collector callback: for each present PTE, collect pte_page() into a dynamically allocated array. The array is freed after the pages are released. Signed-off-by: Baoquan He --- mm/swapfile.c | 51 +++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 45 insertions(+), 6 deletions(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index e0f5fe64de2a..7613ce231d70 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -3776,6 +3776,23 @@ static int xswap_map_clusters(struct swap_info_struct *si, return -ENOMEM; } +struct xswap_page_data { + struct page **pages; + int nr; + int max; +}; + +static int xswap_collect_page(pte_t *pte, unsigned long addr, void *data) +{ + struct xswap_page_data *xpd = data; + + if (!pte_present(*pte)) + return 0; + if (xpd->nr < xpd->max) + xpd->pages[xpd->nr++] = pte_page(*pte); + return 0; +} + static void xswap_unmap_clusters(struct swap_info_struct *si, unsigned long start_idx, unsigned long nr) { @@ -3785,21 +3802,43 @@ static void xswap_unmap_clusters(struct swap_info_struct *si, /* * Round to page boundaries: start up (skip partial page that may * contain clusters still in use before start_idx), end up so the - * entire range is covered. vm_area_unmap_pages() operates on - * whole pages. + * entire range is covered. vm_area_unmap_pages() and + * apply_to_existing_page_range() operate on whole pages. */ unsigned long vm_start = PAGE_ALIGN(start_addr); unsigned long vm_end = PAGE_ALIGN(end_addr); + unsigned long size; + unsigned long npages; + struct xswap_page_data xpd; + int i; if (vm_start >= vm_end) goto out; - vm_area_unmap_pages(si->cluster_vm, vm_start, vm_end); + size = vm_end - vm_start; + npages = size >> PAGE_SHIFT; + /* - * vm_area_unmap_pages() only clears PTEs; it does not free the - * physical pages. Walk the page table to find and free them. + * Walk the page table to collect physical pages before unmapping. + * vm_area_unmap_pages() only clears PTEs and frees intermediate + * page table pages — it does not free backing pages. */ - /* TODO: free backing pages via page table walk or tracking bitmap */ + xpd.pages = kmalloc_array(npages, sizeof(*xpd.pages), GFP_KERNEL); + if (xpd.pages) { + xpd.nr = 0; + xpd.max = npages; + apply_to_existing_page_range(&init_mm, vm_start, size, + xswap_collect_page, &xpd); + } + + vm_area_unmap_pages(si->cluster_vm, vm_start, vm_end); + + /* Free the collected backing pages */ + if (xpd.pages) { + for (i = 0; i < xpd.nr; i++) + __free_page(xpd.pages[i]); + kfree(xpd.pages); + } /* * Pairs with READ_ONCE() in shrink/grow paths. */ -- 2.54.0