From mboxrd@z Thu Jan 1 00:00:00 1970 From: Edward Shishkin Subject: Semantic (mountable) subvolumes in Reiser4 Date: Sat, 30 Jul 2016 11:20:10 +0200 Message-ID: <579C714A.7040304@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject :content-transfer-encoding; bh=F1IYHTRbK+0EUhcaXD2x1by+no9XDc1Fv7zH9zlezNk=; b=oikHniGmOkkhm5dLMOfeI92QAJpa0LKnbe47kMUXgBsJZIBex1zHQaj7JJq2vFjvtG Xz0BZFjormIeXtr+aITU8oiFXzAmg/ArmrHy/adb9A/XD6Vzih/yHfeEqfFhcVN0Un3z GpYFs/2KDBw57Kw3FTvEz+da0IwSWGk7hH9UajLqm75MZHUeIxQSA08BXq8mR1ZO9qZD KpbrsfZfnCxbk2Slcs/Hp47ZC5ldOv6rzTu2lDZap4hUHoCc7PBR5YI218J7mswj0GoE zpLTt2/bdWxkF6u1Hmjejkj3DDDkqOkQdwaCUO9VlexUb4zSOb72lZt82v7Fs5LRL4p8 9kLw== Sender: reiserfs-devel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: ReiserFS development mailing list Semantic (mountable) subvolume is simply a named subtree of the semanic tree. Such subtree has unusual root, which is not refered by the parent directory. That is, parent directory doesn't contain a record about that root. So normally, you can not access this subtree. In order to access a semantic subvolume, you first have to "mount" it. "Mounting" a semantic subvoume creates a reference to its root (specifically, the mount point refers to that root), which makes it accessible. In other bits semantic subvolumes look like usual subtrees of the semantic tree, which are always "visible". Semantic subvolumes is not something new, they are present in some other file systems (though with different names) and have many applications in virtualization (mostly due to their "isolation"). Semantic subvolumes can be easily implemented in Reiser4. if someone cares, then I'll provide details. Thanks, Edward.