From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx176.postini.com [74.125.245.176]) by kanga.kvack.org (Postfix) with SMTP id DD17C6B0044 for ; Mon, 12 Mar 2012 10:02:38 -0400 (EDT) Date: Mon, 12 Mar 2012 15:02:29 +0100 From: Jan Kara Subject: Re: [PATCH 5/9] writeback: introduce the pageout work Message-ID: <20120312140229.GG5998@quack.suse.cz> References: <20120302095910.GB1744@quack.suse.cz> <20120302103951.GA13378@localhost> <20120302115700.7d970497.akpm@linux-foundation.org> <20120303135558.GA9869@localhost> <1331135301.32316.29.camel@sauron.fi.intel.com> <20120309073113.GA5337@localhost> <20120309095135.GC21038@quack.suse.cz> <1331309451.29445.42.camel@sauron.fi.intel.com> <20120309211156.GA6262@quack.suse.cz> <1331555774.12037.9.camel@sauron.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1331555774.12037.9.camel@sauron.fi.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Artem Bityutskiy Cc: Jan Kara , Fengguang Wu , Andrew Morton , Greg Thelen , Ying Han , "hannes@cmpxchg.org" , KAMEZAWA Hiroyuki , Rik van Riel , Mel Gorman , Minchan Kim , Linux Memory Management List , LKML , Adrian Hunter On Mon 12-03-12 14:36:14, Artem Bityutskiy wrote: > On Fri, 2012-03-09 at 22:11 +0100, Jan Kara wrote: > > On Fri 09-03-12 18:10:51, Artem Bityutskiy wrote: > > > On Fri, 2012-03-09 at 10:51 +0100, Jan Kara wrote: > > > > > However I cannot find any ubifs functions to form the above loop, so > > > > > ubifs should be safe for now. > > > > Yeah, me neither but I also failed to find a place where > > > > ubifs_evict_inode() truncates inode space when deleting the inode... Artem? > > > > > > We do call 'truncate_inode_pages()': > > > > > > static void ubifs_evict_inode(struct inode *inode) > > > { > > > ... > > > > > > truncate_inode_pages(&inode->i_data, 0); > > > > > > ... > > > } > > Well, but that just removes pages from page cache. You should somewhere > > also free allocated blocks and free the inode... And I'm sure you do, > > otherwise you would pretty quickly notice that file deletion does not work > > :) Just I could not find which function does it. > > ubifs_evict_inode() -> ubifs_jnl_delete_inode() -> > ubifs_tnc_remove_ino() > > Basically, deletion in UBIFS is about writing a so-called "deletion > inode" to the journal and then removing all the data nodes of the > truncated inode from the TNC (in-memory cache of the FS index, which is > just a huge B-tree, like in reiser4 which inspired me long time ago, and > like in btrfs). > > The second part of the overall deletion job will be when we commit - the > updated version of the FS index will be written to the flash media. Oh, I see. This is what I was missing. And I presume you always make sure to have enough space for new FS index so it cannot deadlock when trying to push out dirty pages. > If we get a power cut before the commit, the journal reply will see the > deletion inode and will clean-up the index. The deletion inode is never > erased before the commit. > > Basically, this design is dictated by the fact that we do not have a > cheap way of doing in-place updates. > > This is a short version of the story. Here are some docs as well: > http://www.linux-mtd.infradead.org/doc/ubifs.html#L_documentation I see. Thanks. Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org