since when does ARM map the kernel memory in sections?
pwaechtler at mac.com
Wed Apr 27 14:50:10 EDT 2011
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).
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