From mboxrd@z Thu Jan 1 00:00:00 1970 From: pwaechtler@mac.com (Peter Waechtler) Date: Wed, 27 Apr 2011 20:50:10 +0200 Subject: since when does ARM map the kernel memory in sections? In-Reply-To: <201104271532.24898.arnd@arndb.de> References: <20110427131905.GF5832@shareable.org> <201104271532.24898.arnd@arndb.de> Message-ID: <201104272050.10644.pwaechtler@mac.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Am Mittwoch, 27. April 2011, 15:32:24 schrieb Arnd Bergmann: > On Wednesday 27 April 2011, Jamie Lokier wrote: > > Imho, only if there's a use for it. If this is about whole partitions > > picking up random data corruption, versus not doing so, then I suggest > > the choice of "Reliable Write" vs. "Unreliable Write" be a mount > > option or hdparm-style block device option. > > > > If there are tighter guarantees, such as "Unreliable Write" corruption > > being limited to the written naturally aligned 1MB blocks (say), and > > it was genuinely faster, that would be really valuable information to > > pass up to filesystems - and to userspace - as you can structure > > reliability around that in lots of ways. > > In all the SDHC cards that I have seen, the corruption should be local to > an erase block of the size that is supposedly found in > /sys/block/mmcblk*/device/preferred_erase_size, which is typically 4 MB. > > However, I don't think that the standard actually guarantees this and, > worse, some cards that I have seen actually lie about the erase block > size and claim that it is 4 MB when it is actually 1.5, 2, 3 or 8 MB. > > For eMMC devices, I don't think we can read the erase block size. > I have to check, but I think to remember that it can be calculated by values provided in CSD/ ex CSD or whatever that acronym was... 4 or 8MB sounds familiar to me (and my problem). Peter