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 A9DDF28682; Mon, 27 Oct 2025 06:58:17 +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=1761548298; cv=none; b=dK8wbTQ4j5UshwzjIs5dKKc12O7U/qC2LdQp1J+qzEJjRAVlQrBYgISsGks5Tjpy24C+ybmgqYthLnvds7ggkerFklPdS0CEkCLu3EizJg/RQ4YpSAueF1TB6qR7eRCdrxM8zqHIgujXUiv8aUtCx6KCRUBHIEUJcPNWz2ol3QM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761548298; c=relaxed/simple; bh=lbGgWupkovq81DImc+Wfj/Z+qTggpqUzQ5AribnsI4Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=dV5ZvtJOA8Kthu4Uha+i/2ASB06y7EJlu2XZlqC0R4MpKloeESiBCGaP6bDtAnhOUDGRhVzqoODh5QzGmf+RdOth+TLqdqfjCsEkePOQaPCADpbt2g/rTl1PJFHJyUsMWQD3xc75sXmYsoIPEAhqHD3CN1JRaxwBL8CUTjxybls= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WgYHd1gR; 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="WgYHd1gR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97AD3C4CEF1; Mon, 27 Oct 2025 06:58:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1761548297; bh=lbGgWupkovq81DImc+Wfj/Z+qTggpqUzQ5AribnsI4Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WgYHd1gRoMxFqKfxyVNMKdMBnx9LTmiWGz9jsusgML8qyb1cDoittaMKbRXdbKibm p3C6RKP/o0JYKQ2ITDj2QPCNF+39qqS3oj+PCGUyAR+Qa7GI0Pd45iPt0aSo3fcOZ1 bOEXHU78SCT2qDR5iScbhySSNt4n9IdSiyHghmqANQwbeVeQK9P9Smyu58ciepIfJR nQLa6zLLFJMopTremXr7vWdGvhdPZL0ze/KJXCQz9zywcVPNoviWG+SMNVygDaaw96 Q8/6D7q2pMOfzkBj6yg1KTjt2J2zW9q4x1RKZ6mXMyH7ijGHy1jJOMEAUGEwZyNbxV ohhV4WLdQZxlw== Date: Mon, 27 Oct 2025 08:58:08 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, pratyush@kernel.org, rdunlap@infradead.org, tj@kernel.org Subject: Re: [PATCH v8 8/8] memblock: Unpreserve memory in case of error Message-ID: References: <20251024161002.747372-1-pasha.tatashin@soleen.com> <20251024161002.747372-9-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Sun, Oct 26, 2025 at 01:41:30PM -0400, Pasha Tatashin wrote: > On Sun, Oct 26, 2025 at 12:29 PM Mike Rapoport wrote: > > > > > @@ -2462,12 +2463,14 @@ static int __init prepare_kho_fdt(void) > > > > > > err |= fdt_begin_node(fdt, ""); > > > err |= fdt_property_string(fdt, "compatible", MEMBLOCK_KHO_NODE_COMPATIBLE); > > > - for (i = 0; i < reserved_mem_count; i++) { > > > + for (i = 0; !err && i < reserved_mem_count; i++) { > > > struct reserve_mem_table *map = &reserved_mem_table[i]; > > > struct page *page = phys_to_page(map->start); > > > unsigned int nr_pages = map->size >> PAGE_SHIFT; > > > > > > - err |= kho_preserve_pages(page, nr_pages); > > > + err = kho_preserve_pages(page, nr_pages); > > > + if (err) > > > + break; > > > > Please > > > > goto err_unpreserve; > > While we can do that, we loose some symmetry of not performing > fdt_end_node() and fdt_finish() if fdt lib ever adds some debugging > facility to make sure that open nodes/trees are properly clodes, this > is going to flag that. I prefer my current implementation. Why do we care about fdt that we are never going to use and that's freed a few lines below? > > > err |= fdt_begin_node(fdt, map->name); > > > err |= fdt_property_string(fdt, "compatible", RESERVE_MEM_KHO_NODE_COMPATIBLE); > > > err |= fdt_property(fdt, "start", &map->start, sizeof(map->start)); > > > > if (err) > > goto err_unpreserve; > > > > and drop !err from the loop condition. > > That is going to miss one 'nr_preserved++' . We cannot do that, we > could move it to the beginning of the loop, but I prefer keeping err > right in the condition. I very much dislike the error handling after this patch. From a single if (err) put_page() it grew into a complex beast with special variables just for the sake of it. What I'd like to see is something like err_unpreserve_fdt: kho_unpreserve_folio(page_folio(fdt_page)); err_unpreserve_mems: for (unsigned int i = 0; i < nr_preserved; i++) { /* unpreserve mem[i] */ } err_free_fdt: put_page(fdt_page); return err; -- Sincerely yours, Mike.