From mboxrd@z Thu Jan 1 00:00:00 1970 From: andreiw@motorola.com (Andrei Warkentin) Date: Thu, 28 Apr 2011 16:38:22 -0500 Subject: since when does ARM map the kernel memory in sections? In-Reply-To: <201104282226.23005.pwaechtler@mac.com> References: <201104282226.23005.pwaechtler@mac.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Apr 28, 2011 at 3:26 PM, Peter Waechtler wrote: > Am Mittwoch, 27. April 2011, 02:27:57 schrieben Sie: >> On Tue, Apr 26, 2011 at 5:58 PM, Jamie Lokier wrote: >> >> Reliable writes are exposed via REQ_FUA. >> > >> > Are you sure that's appropriate? >> > >> > Unless I have misunderstood (very possible), REQ_FUA means writes hit >> > non-volatile storage before acknowledgement, not that they are atomic. >> > I think the normal users of REQ_FUA don't require or expect large >> > atomic writes; they use it as a shortcut for (write & flush this >> > write) without implying anything else is flushed. >> >> I would agree with you that it's not the best mapping. However, a failed >> MMC write transaction has other properties. If I understand correctly, >> depending on mode of failure (say pulling power), you might wind up >> with extra data getting erased (because erase >> happens at erase unit boundary), and erase can be done before all the >> data was transferred from host to card. >> > > No, it's not because of the erase unit size larger than write size. > An "erase unit" is cleared by garbage collection only IFF the complete unit is > unused - asynchronously by the ongoing write transaction. The problem with > damaging neighboring data is: density. No beer (today), i'm drinking wine ;) > > The cells storing the "bits" gets smaller and smaller and with multi level > cells even more bits are represented by "fewer electrons". Programming the > neighbor cell disturbs the fragile cells. If the error correction is disturbed > by power loss: off we go... > > Someone from the flash vendors eavesdropping? Please, pretty please ... :) > > ? ? ? ?Peter > > P.S. Andrei: sorry for reposting, but Kmail confuses me with "Reply to all" > No problem, I'm confused actually if my mails got through... Here and in the other mmc flash reliability thread. A