From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga01.intel.com ([192.55.52.88]) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1WQtwJ-0002m0-81 for linux-mtd@lists.infradead.org; Fri, 21 Mar 2014 07:32:28 +0000 Message-ID: <1395387117.5163.79.camel@sauron.fi.intel.com> Subject: Re: Corrupt empty space From: Artem Bityutskiy To: "Gupta, Pekon" Date: Fri, 21 Mar 2014 09:31:57 +0200 In-Reply-To: <20980858CB6D3A4BAE95CA194937D5E73EAB4DAF@DBDE04.ent.ti.com> References: <1394524000.6302.217.camel@sauron.fi.intel.com> <20980858CB6D3A4BAE95CA194937D5E73EAB4DAF@DBDE04.ent.ti.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Cc: HOUR =?ISO-8859-1?Q?Fr=E9deric?= , Kent Li , "linux-mtd@lists.infradead.org" Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 2014-03-21 at 07:18 +0000, Gupta, Pekon wrote: > It's still getting discussed in [a] and [b]. But there are multiple issues to it. > > (1) Many hardware controllers cannot parse ECC errors in blank-pages. > So, checking number of 0-bits in a page is done in software by comparing > each byte with 0xff. OK. > (2) Counting number of 0-bits in a page in software, brings down your read-performance. UBIFS _only_ needs this when doing recovery, which is _only_ done after unclean reboots, and this kind of reads would be done _only_ for a couple of max I/O units and _only_ if there is a corrupted node in the journal. IOW, this would be done rarely, and for just few pages on mount. -- Best Regards, Artem Bityutskiy