From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.sigma-star.at ([95.130.255.111]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1drmXq-00014L-SJ for linux-mtd@lists.infradead.org; Tue, 12 Sep 2017 14:52:13 +0000 From: Richard Weinberger To: Ricard Wanderlof Cc: dedekind1@gmail.com, Jonas Holmberg , Linux mtd , Cristian Ionescu-Idbohrn Subject: Re: Actual usage of files in ubifs Date: Tue, 12 Sep 2017 16:52:03 +0200 Message-ID: <5426894.QDpU4CeFDX@blindfold> In-Reply-To: References: <1682206.lC8nDS1gi7@blindfold> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Ricard, Am Dienstag, 12. September 2017, 11:15:25 CEST schrieb Ricard Wanderlof: > On Mon, 11 Sep 2017, Richard Weinberger wrote: > > Am Montag, 11. September 2017, 17:44:09 CEST schrieb Artem Bityutskiy: > > > > Good point. I was solely thinking along the lines of how much space > > > > the > > > > actual file occupied, not considering metadata. That would be a good > > > > starting point. I'm guessing that for moderate file sizes the > > > > metadata > > > > would be relatively small compared to the file itself? > > > > > > I would think a "slow" version of this would not be that hard to > > > implement - walk the index and sum up node sizes. Subtract header sizes > > > if you do not want metadata. > > > > > > I am not sure what would be the API? Do other FSes implement something > > > like this? > > > > I think a "show MTD usage by inode" should be implementable via debugfs. > > Maybe, after a discussion on linux-fsdevel a per-file ioctl(). > > > > But first I'd like to know more about the use-case and where to draw the > > border. e.g. If a file as xattrs, do you also account them? UBIFS > > modules xattrs via inodes. So, they have a rather huge space overhead. > > In our specific situation the use case is basically that given a specific > set files (in the root file system), how much flash is actually needed, > also considering that different types of files have different compression > ratios depending on the content. I.e. a large text file might not hurt as > much as a large binary since the former compresses better. > > So primarily it is the total amount needed for the whole file system, but > it quickly comes down how much individual files consume. In our case it's > not necessary to do the operation on a running file system, but in the > more general case that might be more useful. > > I would think that this is something that is known somewhere inside > mkfs.ubifs, or is the information too convoluted to be easily extractable? Adding this to mkfs.ubifs shouldn't be a big deal. And I agree your use case makes sense. Do you want to send me a patch? :) Thanks, //richard -- sigma star gmbh - Eduard-Bodem-Gasse 6 - 6020 Innsbruck - Austria ATU66964118 - FN 374287y