From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.imc-berlin.de ([217.110.46.186]) by canuck.infradead.org with esmtp (Exim 4.43 #1 (Red Hat Linux)) id 1Coj7z-0000qr-G4 for linux-mtd@lists.infradead.org; Wed, 12 Jan 2005 09:05:40 -0500 Message-ID: <41E52EAD.2090302@imc-berlin.de> Date: Wed, 12 Jan 2005 15:05:33 +0100 From: Steven Scholz MIME-Version: 1.0 To: Ferenc Havasi References: <41E4D6E5.1090407@imc-berlin.de> <41E4EDBE.8070302@inf.u-szeged.hu> In-Reply-To: <41E4EDBE.8070302@inf.u-szeged.hu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-mtd@lists.infradead.org Subject: Re: JFFS2: checking CRCs twice!? List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Ferenc, Ferenc Havasi wrote: > If I am right there are two kind of CRC: hdr_crc and node_crc. At > mounting time only the hdr_crc is checked which depends on only the > header. (using summary there is only one summary CRC check) > > Later (when the data is readed or in the background by GC) the node_crc > will also be checked. GC is running on a "niced" (10) priority, so it > should not disturb any other process. Well, it does. On small, slow systems. > If I am right the CRC protects against unclean reboots and hardware > corruptions. If you need we can modify the summary patch not to check > node_crc for summarized nodes (where the unclean reboots is no problem), That would be nice. > but if we do it you lose the ability to detect the hardware corruption > (flash errors). Unfortunatelly NOR flash doesn't have any error detection. Well. I think when a sectors gots written correctly (and summary is correct), I have to assume that the sector stay intact. So no need for checks. If a sector got broken just by reading it then the whole embedded system is broken and has to be replaced ... -- Steven Scholz