From: Jan Kara Subject: Re: [v8 4/5] ext4: adds FS_IOC_FSSETXATTR/FS_IOC_FSGETXATTR interface support Date: Thu, 5 Feb 2015 17:38:15 +0100 Message-ID: <20150205163815.GK4258@quack.suse.cz> References: <54C11733.7080801@yandex-team.ru> <20150123015307.GD24722@dastard> <54C23751.7000009@yandex-team.ru> <20150123233026.GP16552@dastard> <20150127080239.GQ16552@dastard> <54C76C3D.4070404@yandex-team.ru> <20150128003746.GR16552@dastard> <54D23919.3000408@yandex-team.ru> <20150204225844.GA12722@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Konstantin Khlebnikov , Andy Lutomirski , Li Xi , Linux FS Devel , "linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Linux API , Theodore Ts'o , Andreas Dilger , Jan Kara , Al Viro , Christoph Hellwig , dmonakhov-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, "Eric W. Biederman" To: Dave Chinner Return-path: Content-Disposition: inline In-Reply-To: <20150204225844.GA12722@dastard> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org Hello, > Users have *always* been allowed to set the project ID of > their own files. How else are they going to set the project ID on > files they create in random directories so to account them to the > correct project they are working on? > > However, you keep making the assumption that project quotas == > directory subtree quotas. Project quotas are *not limited* to > directory subtrees - the subtree quota implementation is just an > implementation that *sets the default project ID* on files as they > are created. > > e.g. there are production systems out there where project quotas are > used to track home directory space usage rather than user quotas. > This means users can take actions like "this file actually belongs > to project X and it shouldn't be accounted against my home > directory". Users can create their own sub directories that account > everything by default to project X rather than their own home > directory. > > Again: project quotas are an *accounting* mechanism, not a security > mechanism. OK, but now I got confused ;) So if users can change project ID of files they own, what's the point of project quotas? If I need to create a file and project quota doesn't allow me, I just set its project ID to some random number and I'm done with that... So are really project quotas just "advisory" - i.e., all users of a system cooperate so that project X doesn't use more space than it should (and project quotas make this cooperation somewhat simpler) or is there something which limits which project IDs user can set? I didn't find anything... Honza -- Jan Kara SUSE Labs, CR