From patchwork Fri Oct 6 02:45:31 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Pitre X-Patchwork-Id: 115020 Delivered-To: patch@linaro.org Received: by 10.140.22.163 with SMTP id 32csp1270622qgn; Thu, 5 Oct 2017 19:46:29 -0700 (PDT) X-Google-Smtp-Source: AOwi7QAPlcXW8ra1ToGfd98c18cUaM1jqFEGHlaF9ualnn4cWssd3etG3h1DTvVN/2pQRi6iepAh X-Received: by 10.101.83.4 with SMTP id m4mr628114pgq.266.1507257989873; Thu, 05 Oct 2017 19:46:29 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1507257989; cv=none; d=google.com; s=arc-20160816; b=qh/8RstErQUTneJHBaqlXz4+vHATh94q/D9rQRC3xMS0PSS/jwxHNLlYLYZo8AI48j Zg3GfniJqDvzcMxVTN8wNeev2c/hfwUwzDrgcR/n7PeEbbDSoMx35hO8DEXD5j/i6AMp BeifCxsdOr4DnMpeSqSzK8/erjVN1qHrv/v0/2+1wKRxYHpbb0Gx0bZbmFMCgdFzwrGz wtxiTXjePJtUDDEkUYc7Ayc30wfivi8ShcGeetIThC4GxLXbVvFosMz4T7ZTfvaunZRh 1LN2POfTjMh6+xCvEINd6fqC/eFVdOyiod8uPvz12+XKf0mIERNdghJ4LwEU79/4eHD0 NY6w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=EA55KHDmQ7ayh5wcaphD1tiD0hZALg0qUBQwUe33q6E=; b=gN7cvmQ2jAsIcuWV4r2AWOow49NBVxVD71WKlt+Y38qUtESJOl40DTbEkx806Pz+u8 fA6Yu+mf1hRmK9viznJKTE67UfjjgjaVxb86V+8AslZ0f79RqqLid6J/h4gpdTlkqcal phap0HLpOlmzZA/rMm4upJc0q6x9h6M9mtiEhti4SPklBJrCd5loIbXjLEhFYD15b0pw pEiOvcZdXwc9fsvofEeJfFpFse0zvtil2gAv8DSzeA0KzdkYvK2agj80fJ4VybACw3Hp Q49pjdaer8HIOjh8cdeWfAqNpFFd5c4tqjK0xpEsJaN5qM58mVR0xfmZBhwe18jhVdfZ WX8w== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=VTA0rIM0; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id c2si354794pfj.240.2017.10.05.19.46.29; Thu, 05 Oct 2017 19:46:29 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@pobox.com header.s=sasl header.b=VTA0rIM0; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751932AbdJFCq1 (ORCPT + 26 others); Thu, 5 Oct 2017 22:46:27 -0400 Received: from pb-smtp1.pobox.com ([64.147.108.70]:52534 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751536AbdJFCpk (ORCPT ); Thu, 5 Oct 2017 22:45:40 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 5B46B99B17; Thu, 5 Oct 2017 22:45:39 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:date:message-id:in-reply-to:references; s=sasl; bh=yq1d /lUsoFpCSBXkNr5MfSp2YVk=; b=VTA0rIM0CNCR+4qoNlHPABhZ+8+b/LlCvyMb Yfos3KqKlmhMDrw5IQD2q5f8ZwDfSZKfZepSspA7d5K3y7i4nbblwlWSwjy2uDL/ J3zEr9QaEAMnGUE5JKSweL9dnfO/m+2Jl4+F0xUSGSVtSxHK59lb9meVQ1Pxnr7q UIbAVW4= Received: from pb-smtp1.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp1.pobox.com (Postfix) with ESMTP id 5342699B16; Thu, 5 Oct 2017 22:45:39 -0400 (EDT) Received: from yoda.home (unknown [137.175.234.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp1.pobox.com (Postfix) with ESMTPSA id D5EAD99B11; Thu, 5 Oct 2017 22:45:38 -0400 (EDT) Received: from xanadu.home (xanadu.home [192.168.2.2]) by yoda.home (Postfix) with ESMTP id 00F272DA06E6; Thu, 5 Oct 2017 22:45:38 -0400 (EDT) From: Nicolas Pitre To: Alexander Viro , Christoph Hellwig Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-embedded@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Brandt Subject: [PATCH v5 5/5] cramfs: rehabilitate it Date: Thu, 5 Oct 2017 22:45:31 -0400 Message-Id: <20171006024531.8885-6-nicolas.pitre@linaro.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20171006024531.8885-1-nicolas.pitre@linaro.org> References: <20171006024531.8885-1-nicolas.pitre@linaro.org> X-Pobox-Relay-ID: 6FD482C4-AA40-11E7-AEDC-8EF31968708C-78420484!pb-smtp1.pobox.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Update documentation, pointer to latest tools, appoint myself as maintainer. Given it's been unloved for so long, I don't expect anyone will protest. Signed-off-by: Nicolas Pitre Tested-by: Chris Brandt --- Documentation/filesystems/cramfs.txt | 42 ++++++++++++++++++++++++++++++++++++ MAINTAINERS | 4 ++-- fs/cramfs/Kconfig | 9 +++++--- 3 files changed, 50 insertions(+), 5 deletions(-) -- 2.9.5 diff --git a/Documentation/filesystems/cramfs.txt b/Documentation/filesystems/cramfs.txt index 4006298f67..8875d306bc 100644 --- a/Documentation/filesystems/cramfs.txt +++ b/Documentation/filesystems/cramfs.txt @@ -45,6 +45,48 @@ you can just change the #define in mkcramfs.c, so long as you don't mind the filesystem becoming unreadable to future kernels. +Memory Mapped cramfs image +-------------------------- + +The CRAMFS_PHYSMEM Kconfig option adds support for loading data directly +from a physical linear memory range (usually non volatile memory like Flash) +to cramfs instead of going through the block device layer. This saves some +memory since no intermediate buffering is necessary to hold the data before +decompressing. + +And when data blocks are kept uncompressed and properly aligned, they will +automatically be mapped directly into user space whenever possible providing +eXecute-In-Place (XIP) from ROM of read-only segments. Data segments mapped +read-write (hence they have to be copied to RAM) may still be compressed in +the cramfs image in the same file along with non compressed read-only +segments. Both MMU and no-MMU systems are supported. This is particularly +handy for tiny embedded systems with very tight memory constraints. + +The filesystem type for this feature is "cramfs_physmem" to distinguish it +from the block device (or MTD) based access. The location of the cramfs +image in memory is system dependent. You must know the proper physical +address where the cramfs image is located and specify it using the +physaddr=0x******** mount option (for example, if the physical address +of the cramfs image is 0x80100000, the following command would mount it +on /mnt: + +$ mount -t cramfs_physmem -o physaddr=0x80100000 none /mnt + +To boot such an image as the root filesystem, the following kernel +commandline parameters must be provided: + + "rootfstype=cramfs_physmem rootflags=physaddr=0x80100000" + + +Tools +----- + +A version of mkcramfs that can take advantage of the latest capabilities +described above can be found here: + +https://github.com/npitre/cramfs-tools + + For /usr/share/magic -------------------- diff --git a/MAINTAINERS b/MAINTAINERS index 1c3feffb1c..f00aec6a66 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3612,8 +3612,8 @@ F: drivers/cpuidle/* F: include/linux/cpuidle.h CRAMFS FILESYSTEM -W: http://sourceforge.net/projects/cramfs/ -S: Orphan / Obsolete +M: Nicolas Pitre +S: Maintained F: Documentation/filesystems/cramfs.txt F: fs/cramfs/ diff --git a/fs/cramfs/Kconfig b/fs/cramfs/Kconfig index 5b4e0b7e13..ae1fe6c795 100644 --- a/fs/cramfs/Kconfig +++ b/fs/cramfs/Kconfig @@ -1,5 +1,5 @@ config CRAMFS - tristate "Compressed ROM file system support (cramfs) (OBSOLETE)" + tristate "Compressed ROM file system support (cramfs)" select ZLIB_INFLATE help Saying Y here includes support for CramFs (Compressed ROM File @@ -15,8 +15,11 @@ config CRAMFS cramfs. Note that the root file system (the one containing the directory /) cannot be compiled as a module. - This filesystem is obsoleted by SquashFS, which is much better - in terms of performance and features. + This filesystem is limited in capabilities and performance on + purpose to remain small and low on RAM usage. It is most suitable + for small embedded systems. For a more capable compressed filesystem + you should look at SquashFS which is much better in terms of + performance and features. If unsure, say N.