From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wy0-f177.google.com ([74.125.82.177]) by canuck.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1REdTy-00011a-0M for linux-mtd@lists.infradead.org; Fri, 14 Oct 2011 08:51:11 +0000 Received: by wyi11 with SMTP id 11so3416400wyi.36 for ; Fri, 14 Oct 2011 01:51:08 -0700 (PDT) Subject: Re: [PATCH] jffs2: allow disabling of compression schemes at runtime From: Artem Bityutskiy To: Andres Salomon Date: Fri, 14 Oct 2011 11:50:37 +0300 In-Reply-To: <20111003191624.7efd3dce@queued.net> References: <20111003191624.7efd3dce@queued.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Message-ID: <1318582244.12351.73.camel@sauron> Mime-Version: 1.0 Cc: linux-mtd@lists.infradead.org, David Woodhouse , linux-kernel@vger.kernel.org Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2011-10-03 at 19:16 -0700, Andres Salomon wrote: > Currently jffs2 has compile-time constants (and .config options) > regarding whether or not the various compression/decompression > drivers are built in and enabled. This is fine for embedded > systems, but it clashes with distribution kernels. Distro kernels > tend to turn on everything; this causes OpenFirmware to fall > over, as it only supports ZLIB decompression. Booting a kernel > that has LZO compression enabled, writing to the boot partition, > and then rebooting causes OFW to fail to read the kernel from > the filesystem. This is because LZO compression has priority > when writing new data to jffs2, if LZO is enabled. > > To get around that, this patch adds jffs2 module params for each > compressor type that isn't decompression-only. That means I can run > a kernel that has support for LZO and ZLIB decompression (allowing > me to read LZO data off of the root partition), while disabling > LZO compression writes (jffs2.disable_lzo=1) so that the boot > partition stays compatible with OFW. > > Signed-off-by: Andres Salomon You should use mount options instead. Invent nice mount options to configure compression strategy of JFFS2. Or you can simply implement the same option as UBIFS has: compr=xxx. See Documentation/filesystems/ubifs.txt With this option you set the default compressor which is use when writing, and on reading all decompression are supported, seems like exactly what you want. You can also look how it is implemented in UBIFS for reference. -- Best Regards, Artem Bityutskiy