From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from majordomo by infradead.org with local (Exim 3.03 #1) id 13Jzgn-0002j8-00 for mtd-list@infradead.org; Wed, 02 Aug 2000 15:40:09 +0100 Received: from dns.cygnus.co.uk ([194.130.39.3] helo=pasanda.cygnus.co.uk) by infradead.org with smtp (Exim 3.03 #1) id 13Jzgm-0002j2-00 for mtd@infradead.org; Wed, 02 Aug 2000 15:40:08 +0100 From: David Woodhouse In-Reply-To: References: To: Alexander Larsson Cc: Markus Thiesmeyer , mtd@infradead.org, jffs-dev@axis.com, bmatthews@redhat.com Subject: Re: Is JFFS a full featured filesystem? Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Wed, 02 Aug 2000 15:20:04 +0100 Message-ID: <24735.965226004@cygnus.co.uk> Sender: owner-mtd@infradead.org List-ID: alex@cendio.se said: > Exactly how did you plan to work out the dirty ranges? Compare with > on-flash contents? Apparently it's easy when using generic_file_write, because prepare_write will give you the exact range. When doing writable mmap() we have to do something cleverer - basically yes, comparing with the on-flash contents. We can either do that by going and reading the flash nodes again on writepage(), or we can keep a copy of the clean page in RAM before it's dirtied. To start with, I'm inclined just to accept the hit of the 4Kb writes, and let the GC combine nodes later as necessary. Comparing with old contents can come later. This is only going to be a problem with writable mmap(), which isn't supported at the moment _anyway_. The normal write() case is fairly simple to optimise. -- dwmw2 To unsubscribe, send "unsubscribe mtd" to majordomo@infradead.org