From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from a.ns.miles-group.at ([95.130.255.143] helo=radon.swed.at) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ajC1X-0005RB-Ed for linux-mtd@lists.infradead.org; Thu, 24 Mar 2016 20:38:32 +0000 Subject: Re: ubiblock RW To: Ezequiel Garcia , Benson Young References: Cc: "linux-mtd@lists.infradead.org" , David Gstir From: Richard Weinberger Message-ID: <56F4502D.3030902@nod.at> Date: Thu, 24 Mar 2016 21:38:05 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi! Am 24.03.2016 um 15:23 schrieb Ezequiel Garcia: > +MTD > > On 23 March 2016 at 14:40, Benson Young wrote: >> Hello Ezequiel, >> >> I came upon the discussion about block device emulation over UBI. >> http://linux-mtd.infradead.narkive.com/YF0XOFxY/block-device-emulation-on-top-of-ubi-volumes-with-read-write-support >> >> I understand the most recent implementation is read-only emulation for >> mounting squashfs based file system. >> However, I would really like to see the write option be brought back. If >> not, can you please help me about enabling the write option in my build? >> I have used the patch listed in the following link >> https://lwn.net/Articles/525957/ >> but i couldn't find any accompanying util that allows me to create the ubi >> block volume. >> > > You should be able to use mtd-utils' ubiblock tool (maybe you'll need to do > some modifications). > > http://www.linux-mtd.infradead.org/doc/ubi.html#L_ubiblock > >> Reason for this request is that I am looking into root file system >> encryption over un-managed NAND flash. Now the mainline method of disk >> encryption in Linux revolves around >> dm-crypt module which requires a block device. i am under the impression >> that using mtdblock works to an extent until the partition you try to >> map/encrypt has bad blocks in it. >> I have seen discussion about using UBIFS, and I have seen a paper discussing >> it, where the author embeds the encryption engine within UBI layer, so each >> write and read is encrypted. However, its a path I would take when I have no >> choice. Right now dm-crypt is my first choice basically because of the >> availability of support/discussion/information. >> >> I also saw you mentioned that you don't have NAND flash for testing, this is >> something that I can help with. I have an abundance of NAND flash devices. > > I have some devices with SLC NANDs now, but thanks for the offer. > >> For simplicity sake, I work with SLC because of better endurance compared to >> MLC. I am also curious about flash endurance with EXT4 over UBI. Destructive >> erase/write will definitely on my to-do list. >> > > So, like I said here: > > http://linux-mtd.infradead.narkive.com/YF0XOFxY/block-device-emulation-on-top-of-ubi-volumes-with-read-write-support > > We can definitely implement write support if we have a good use case for it. > Encryption might be one. > > Richard, what do you think? I'm definitely not fond of adding write support to ubiblock without turning it into a proper FTL. Otherwise it will be abused and will cause serious damage. Regarding encryption, encryption for UBIFS is in the pipes, Dave and I did already some preliminary work. It will materialize within this year, depending on how much we get distracted by other projects. So far it is a spare time project. The plan is adding file level encryption like ext4 and f2fs have. Thanks, //richard