From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9FCCC4332F for ; Wed, 9 Nov 2022 17:21:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230041AbiKIRVP (ORCPT ); Wed, 9 Nov 2022 12:21:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229750AbiKIRVO (ORCPT ); Wed, 9 Nov 2022 12:21:14 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 551E125C8; Wed, 9 Nov 2022 09:21:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=U8E7Jm8e1876qUqey5/8BiJLc1XaDBvWcjC7yx9ROzg=; b=gmH5h/mQ6qEquszdoCqVrpILhD iK+Kn9JHkuehJ2b1rL/vezAXYWk0g3pgHr7Iy/bU1gc3he4FIVq3yXOY55t5UfEjBxHetnvUf7TEN sA7IMRXPsK/N42x13tITnCCN/virflVFzUjbq/NWOF+5NR7/TJJCqt76qufO0ugPmwCpdfJJivc5a osQkbkyKeXSgy0E4O0x9ZfTPlAFK/2N170Qq7YhrJqYEP+1KaiC2loLtcK8AdIBu3jn/6awOQon6Z jv7RxpJFjzlqVSJ4ty0ykIzFEYXt2wMLx5Hh5VwgxdpsOcaf/3h9HS4qDfKuj4uHxAEnu4qohzwjs 2sB3e4pQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1osol3-00BLdJ-H0; Wed, 09 Nov 2022 17:21:01 +0000 Date: Wed, 9 Nov 2022 17:21:01 +0000 From: Matthew Wilcox To: Daniel Golle Cc: Jens Axboe , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra , Davidlohr Bueso , "Martin K. Petersen" , Chaitanya Kulkarni , Ming Lei , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-efi@vger.kernel.org Subject: Re: [PATCH v4 2/5] block: add partition parser for U-Boot uImage.FIT Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org On Wed, Nov 09, 2022 at 02:36:11PM +0000, Daniel Golle wrote: > On Wed, Nov 09, 2022 at 01:58:29PM +0000, Matthew Wilcox wrote: > > ... actually, why can't you call read_part_sector() and avoid all of > > this? > > I've tried that before and the problem is that read_part_sector() > returns a pointer to one sector (typically 512 bytes) of data. > And this pointer should not be accesses beyond sector boundaries, > right? You'd have to call read_part_sector() again for the next > sector. > > The FIT structure, however, usually exceeds the size of one sector, > and having a continous memory area covering the structure as a whole > is crucial for libfdt to do its job. > > I could, of course, use read_part_sector() to copy all sectors > covering the FIT structure into a buffer, but that seemed strange > given that read_part_sector() actually used read_mapping_page() > (and now uses read_mapping_folio()) internally and then returns a > pointer to the offset within the page/folio. So why not read it in one > piece in first place instead of having it first split up to sectors > by read_part_sector() just to then having to reassemble it into a > continous buffer again. Are you guaranteed that it's "sufficiently" aligned on storage so that it fits entirely within a single page? If not, you'll have to copy it, vmap it, or fix libfdt to handle a segmented buffer.