From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D239D2D46A4 for ; Wed, 17 Sep 2025 14:31:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758119511; cv=none; b=KjiCCNWS+oX1UtYAdiqd+JZtRKYlKmNX+Z2DFVe20BSn0eCuhl8e/zQpBzVSWp67hAKwg4ZBrm4nqFyf+p4zkVayp6eYXqG1cVkiFP63WKTjiJvCR8AyGA4HJqH3yjVJaIVhkFFjh4dmAD9Zyabnlgy56cEMUzmtVTO7u4kCZi8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758119511; c=relaxed/simple; bh=k9cG3kz/ofV3MOY4tO3NxTa8C0lQ0KwhYvMThaTJklY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uyvhNIW8LrQsqikfoCkp07jYViDbxa3jYmMqKI720MsuXVAIMv6SxgyoK1CnSonUdDa4KDsNbg2E8GnMdsoAipCT+2ENmJ5JnlV7ikKhnAitb0J1fzcl+aQH6hH5lWtXQWYv6rSGLWey13HaKAfGLqZFeRi7ty+96WT3FWaep+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sQEqNcn0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sQEqNcn0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6FADCC4CEF5; Wed, 17 Sep 2025 14:31:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758119511; bh=k9cG3kz/ofV3MOY4tO3NxTa8C0lQ0KwhYvMThaTJklY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sQEqNcn0RVU/IcZMKtRGuPfTEkCa0ftTy/KsYvzMc3vySV8NIyQSfoyOOB2AZ0qf7 uvKDbh8G2D1egXCoXYyAkAROQqrV/L6uYZ7WwgHjGV6vU8XN/U2gdNN/81/ykgz74x BKM5zcBdLMGa9+WaH5hvAylH3sHfMjkc4ahHvOAvCLfYgVwBPOFIVTbNicQsvWEIor nkYqUQw2pr2C/CaUkc+/SWb3ZjvoyWXxJZ8jQhUlkTcGlL0mShtgbI6PzxxuQVbuiO duNhZzx8ephb7lWkr8DQmTnrYbA5pTXGmjtpRlB4u3M1eBQqoK/0aWk+CWHFSahNCV GweR5D4v6nbEA== Date: Wed, 17 Sep 2025 17:31:43 +0300 From: Mike Rapoport To: Pratyush Yadav Cc: Alexander Graf , Changyuan Lyu , Andrew Morton , Baoquan He , Pasha Tatashin , Jason Gunthorpe , Chris Li , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/2] kho: move sanity checks to kho_restore_page() Message-ID: References: <20250917125725.665-1-pratyush@kernel.org> 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=us-ascii Content-Disposition: inline In-Reply-To: <20250917125725.665-1-pratyush@kernel.org> On Wed, Sep 17, 2025 at 02:56:53PM +0200, Pratyush Yadav wrote: > While KHO exposes folio as the primitive externally, internally its > restoration machinery operates on pages. This can be seen with > kho_restore_folio() for example. It performs some sanity checks and > hands it over to kho_restore_page() to do the heavy lifting of page > restoration. After the work done by kho_restore_page(), > kho_restore_folio() only converts the head page to folio and returns it. > Similarly, deserialize_bitmap() operates on the head page directly to > store the order. > > Move the sanity checks for valid phys and order from the public-facing > kho_restore_folio() to the private-facing kho_restore_page(). This makes > the boundary between page and folio clearer from KHO's perspective. > > While at it, drop the comment above kho_restore_page(). The comment is > misleading now. The function stopped looking like free_reserved_page() > since 12b9a2c05d1b4 ("kho: initialize tail pages for higher order folios > properly"), and now looks even more different. > > Signed-off-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) > --- > > Notes: > Changes in v2: > > - New in v2. > > kernel/kexec_handover.c | 28 ++++++++++++++-------------- > 1 file changed, 14 insertions(+), 14 deletions(-) > > diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c > index ecd1ac210dbd7..69cab82abaaef 100644 > --- a/kernel/kexec_handover.c > +++ b/kernel/kexec_handover.c > @@ -183,10 +183,18 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn, > return 0; > } > > -/* almost as free_reserved_page(), just don't free the page */ > -static void kho_restore_page(struct page *page, unsigned int order) > +static struct page *kho_restore_page(phys_addr_t phys) > { > - unsigned int nr_pages = (1 << order); > + struct page *page = pfn_to_online_page(PHYS_PFN(phys)); > + unsigned int nr_pages, order; > + > + if (!page) > + return NULL; > + > + order = page->private; > + if (order > MAX_PAGE_ORDER) > + return NULL; > + nr_pages = (1 << order); > > /* Head page gets refcount of 1. */ > set_page_count(page, 1); > @@ -199,6 +207,7 @@ static void kho_restore_page(struct page *page, unsigned int order) > prep_compound_page(page, order); > > adjust_managed_page_count(page, nr_pages); > + return page; > } > > /** > @@ -209,18 +218,9 @@ static void kho_restore_page(struct page *page, unsigned int order) > */ > struct folio *kho_restore_folio(phys_addr_t phys) > { > - struct page *page = pfn_to_online_page(PHYS_PFN(phys)); > - unsigned long order; > - > - if (!page) > - return NULL; > - > - order = page->private; > - if (order > MAX_PAGE_ORDER) > - return NULL; > + struct page *page = kho_restore_page(phys); > > - kho_restore_page(page, order); > - return page_folio(page); > + return page ? page_folio(page) : NULL; > } > EXPORT_SYMBOL_GPL(kho_restore_folio); > > -- > 2.47.3 > -- Sincerely yours, Mike.