From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-199112-1520461872-2-3359096215038275780 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, SPF_PASS -0.001, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='62.4.15.54', Host='mail.bootlin.com', Country='FR', FromHeader='com', MailFrom='com' X-Spam-charsets: plain='US-ASCII' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: boris.brezillon@bootlin.com ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1520461871; b=IZzzGilOmc9LYAt+xhSbeviW1qxAZQVFzYFWhXAaLfc3SZ/ GplCKtZSljZopbXY029z9yRCNT+uuTEJduWnOm2Jec5HJz7txp3d6RMSdnhGNm5H 3w0YwECENKgPBEpntnFa3AjF/V8IfDokxOYzUuY3iLSzJFql7cRlASLakoLZat/v dmRET3Zv2Krr2FhD2FsodqWwNdtcsCqx4EkwSQYphqrArMDg29D3hcGexZj8/EPa iGqLyr59MZIEsFYQ61snuNurqEqgUViuxoQMYMvdB5ebLF/j2IQFkk+Ra8uYDpYj 2NZnBnrMlkjoKCmKgHtt4xF0ydUTMYCGpTFsaQA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :in-reply-to:references:mime-version:content-type :content-transfer-encoding; s=arctest; t=1520461871; bh=IQlJScVM RRLCSVTN2qpEkGblr/NfPUvJQBcN4d6mL/A=; b=P4kpfqBJ8bIZY0td/Y69T8+V MnHsKoAvukUF0pTMXlzEAuyzwbSjj+NX5n6Q661isT4LqezExdGPHGWR4babVczG zW+vn9RXWVPrM4PkBwISr6t81SIaWuueViOL9+SiHZRzH5V0BeNmXQvHbkHuU+jf lEyX/yOcXsfIKZjvlxmAN/W92TU8DMj9OcEYGrqfG9+HsiNmbTLez315JQU0f6B9 Ti/f4QEyzWbuSXEpD5QnYVWY0ErmDb97GpJ6ZFS7bp8VSUHboJ78EaeVW7pvDd+d IpjQ3c699ocfBGPz983ES0SyhH3pZ08gKoWhom5d98Gi2fkzw1fCoX75X8n89Q== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,d=none) header.from=bootlin.com; iprev=pass policy.iprev=62.4.15.54 (mail.bootlin.com); spf=pass smtp.mailfrom=boris.brezillon@bootlin.com smtp.helo=mail.bootlin.com; x-aligned-from=pass; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=mail.bootlin.com x-ptr-lookup=mail.bootlin.com; x-return-mx=pass smtp.domain=bootlin.com smtp.result=pass smtp_is_org_domain=yes header.domain=bootlin.com header.result=pass header_is_org_domain=yes Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=none (p=none,d=none) header.from=bootlin.com; iprev=pass policy.iprev=62.4.15.54 (mail.bootlin.com); spf=pass smtp.mailfrom=boris.brezillon@bootlin.com smtp.helo=mail.bootlin.com; x-aligned-from=pass; x-category=clean score=-100 state=0; x-ptr=pass x-ptr-helo=mail.bootlin.com x-ptr-lookup=mail.bootlin.com; x-return-mx=pass smtp.domain=bootlin.com smtp.result=pass smtp_is_org_domain=yes header.domain=bootlin.com header.result=pass header_is_org_domain=yes X-Remote-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on mail.bootlin.com X-Remote-Spam-Level: X-Remote-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,SHORTCIRCUIT, URIBL_BLOCKED shortcircuit=ham autolearn=disabled version=3.4.0 Date: Wed, 7 Mar 2018 23:30:57 +0100 From: Boris Brezillon To: Pavel Machek Cc: David Woodhouse , Greg KH , Steve deRosier , Richard Weinberger , Boris Brezillon , dedekind1@gmail.com, tharvey@gateworks.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, marek.vasut@gmail.com, linux-mtd@lists.infradead.org, cyrille.pitchen@wedev4u.fr, computersforpeace@gmail.com Subject: Re: [PATCH] ubi: Reject MLC NAND Message-ID: <20180307233057.54bd35c3@bbrezillon> In-Reply-To: <20180307221733.GE10438@amd> References: <20180303104554.5958-1-richard@nod.at> <20180306231805.GA28183@amd> <6772577.AmT7QaWTNU@blindfold> <20180307214342.GA9852@amd> <1520460673.31298.136.camel@infradead.org> <20180307221733.GE10438@amd> X-Mailer: Claws Mail 3.15.0-dirty (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Hi Pavel, On Wed, 7 Mar 2018 23:17:33 +0100 Pavel Machek wrote: > On Wed 2018-03-07 22:11:13, David Woodhouse wrote: > > > > > > On Wed, 2018-03-07 at 14:08 -0800, Steve deRosier wrote: > > > > > > To clarify one thing: the reason for this is MLC has actually never > > > been supported, nor worked properly. The fact that it kinda worked was > > > incidental and the cause of major problems for people due to that not > > > being clear. This patch only makes it explicit and avoids people > > > mistakenly trying to use UBIFS on MLC flash and risking their data and > > > products. To me, that's what's important. > > > > > > This is an important patch, even if all it does is keep people from > > > loosing data. It also changes the conversation from "I have a > > > corrupted UBIFS device, BTW it's on MLC..." to "What can we do to get > > > UBIFS to work on MLC". > > Well, for -stable I'd suggest printk(KERN_ALERT ...) but keep the > system running. > > > This is a bug fix. > > > > UBI on MLC never worked. It was a bug that we ever permitted it. This > > is now fixed. > > Yeah, well, so lets say I have a working hardware (maybe using > read-only UBI on MLC), update to next stable kernel, and now kernel > refuses to see the partition. Read-only does not save you from the read-disturb issue, and you even have to take care of programming the full erase-block on some MLC NANDs, which AFAIR is not done when updating a static volume. I have one simple question: did you ever play with MLC NANDs or are you just trolling? If you had, like Richard and I did when working on MLC support, I'm pretty sure you wouldn't play this "don't backport to stable" card. Now, if you volunteer to add reliable MLC support, I can send you a few boards to play with. I even have a "working but not so tested PoC" here [1] if you want to finish the job, but please don't do the mistake of thinking the fix is that simple. > > I'll certainly not consider this patch a bug fix. And apparently a lot of people disagree with you on this point, and I guess all of them had problems with MLC NANDs. > > Removing support for hardware that "only works by mistake" may be good > idea, but maybe it is slightly too surprising for a -stable. I wouldn't say "work by mistake" but "seems to work at first but in the end breaks", so definitely a candidate for -stable IMO. Regards, Boris [1]https://github.com/bbrezillon/linux/tree/nand/mlc -- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com