From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from a.ns.miles-group.at ([95.130.255.143] helo=radon.swed.at) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1XgFNZ-0003G5-Js for linux-mtd@lists.infradead.org; Mon, 20 Oct 2014 16:00:18 +0000 Message-ID: <54453178.3050903@nod.at> Date: Mon, 20 Oct 2014 17:59:52 +0200 From: Richard Weinberger MIME-Version: 1.0 To: dedekind1@gmail.com Subject: Re: [PATCH 3/4] UBI: Fastmap: Care about the protection queue References: <1412029248-22454-1-git-send-email-richard@nod.at> <1412029248-22454-4-git-send-email-richard@nod.at> <1412346676.3795.62.camel@sauron.fi.intel.com> <542EF3BF.1070401@nod.at> <1413206263.7906.18.camel@sauron.fi.intel.com> <543BE21F.5020504@nod.at> <1413213803.7906.45.camel@sauron.fi.intel.com> <543C3E60.4080507@nod.at> <1413282203.7906.72.camel@sauron.fi.intel.com> <543F9895.7010502@nod.at> <1413816389.7906.336.camel@sauron.fi.intel.com> <544527A3.7030508@nod.at> <1413819635.7906.369.camel@sauron.fi.intel.com> In-Reply-To: <1413819635.7906.369.camel@sauron.fi.intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Am 20.10.2014 um 17:40 schrieb Artem Bityutskiy: > On Mon, 2014-10-20 at 17:17 +0200, Richard Weinberger wrote: >>> That's just fastmap code not doing the right thing. We should not touch >>> the work queue directly at all. What we _should_ do instead is to make >>> it empty by asking the subsystem which manages it to flush it. >>> >>> 1. Lock the work queue to prevent anyone from submitting new jobs while >>> we are in process of writing the fastmap. >>> 2. Flush all works >>> 3. do all the fastmap write stuff >>> 4. Unlock >> >> Are you sure? Flushing all works before every fastmap write will slow UBI down. >> The fastmap write is not cheap. The goal should be to make it faster. > > Yes, you are right. So instead, we wanna "freeze" it, and save all PEBs > the jobs in fastmap too. > > Why 'ubi_write_fastmap()' only cares about the erase jobs, and saves the > PEBs from the job as "must be erased". > > What about the "move" jobs? There are no move jobs. Do you mean ubi->move_from/to used in wear_leveling_worker()? How could it happen that a fastmap is written between these? IIRC everything is done under wl_lock. And the PEBs used have to go through the pool. > Also, say, PEB X is in the work queue waiting for erasure. Fastmap comes > along and saves it as "must be erased" in the fastmap. Fastmap finishes > its job, PEB X gets erased, and I write my data there, so PEB X is > referred to by LEB Y. Now I have power cut. Then I attach the flash > again. Surely it is not that fastmap just erases PEB X and I lose the > contents of LEB Y? This cannot happen. If X is erased you cannot write data do it. I must first go thought the pool and the pool is scanned while attaching. Thanks, //richard