Am 27.11.2014 um 16:27 schrieb Artem Bityutskiy: > On Mon, 2014-11-24 at 14:20 +0100, Richard Weinberger wrote: >> If the WL pool runs out of PEBs we schedule a fastmap write >> to refill it as soon as possible. >> Ensure that only one at a time is scheduled otherwise we might end in >> a fastmap write storm because writing the fastmap can schedule another >> write if bitflips are detected. > > Could you please provide some more details about the "write storm". Does > it happen when there are 2 fastmap works in the queue? Or if they run > simultaneously? Why the storm happens and white kind of "writes" it > consists of?
If UBI needs to write a new fastmap while wear leveling (by using get_peb_for_wl()) a fastmap work is scheduled. We cannot write a fastmap in this context because we're in atomic context. At this point one fastmap write is scheduled. If now get_peb_for_wl() is executed a second time it will schedule another fastmap work because the pools are still not refilled. This will go on until finally a fastmap got written. Either by the the kworker or ubi_wl_get_peb(). As now a lot of fastmap works are scheduled they all will be issues in series. Hence, a write storm. :) Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
