From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Wed, 27 Apr 2011 15:32:24 +0200 Subject: since when does ARM map the kernel memory in sections? In-Reply-To: <20110427131905.GF5832@shareable.org> References: <20110427131905.GF5832@shareable.org> Message-ID: <201104271532.24898.arnd@arndb.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Arnd