From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: [RFC] proposal for a btrfs filesystem layout Date: Fri, 20 Nov 2009 14:50:17 -0500 Message-ID: <20091120195017.GZ3110@think> References: <200911201950.06662.kreijack@libero.it> <934f64a20911201124q2a42fddek87d3f8fe864b3c41@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Goffredo Baroncelli , linux-btrfs@vger.kernel.org, Chris Ball To: David Nicol Return-path: In-Reply-To: <934f64a20911201124q2a42fddek87d3f8fe864b3c41@mail.gmail.com> List-ID: On Fri, Nov 20, 2009 at 01:24:42PM -0600, David Nicol wrote: > On Fri, Nov 20, 2009 at 12:50 PM, Goffredo Baroncelli > wrote: > > > Any comments ? > > BR > > G.Baroncelli > > > since COW semantics require touching directory entries all the way up > to the root of the subvolume, for transaction-intensive applications > it would make sense to provide something that works like "mkdir" but > creates a subvolume that will be mounted at a point rather than a > simple directory entry. To avoid contention serializing updates to the > root directory. Is something like that already in place? COW semantics require touching btree nodes all the way up to the root of the btree, but this is different from the directory. Directories are stored in the btree, but you won't have to touch more than 8 or so btree levels regardless of how deep your directory tree is. -chris