From: Christoph Hellwig Subject: Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separate super_operation Date: Fri, 19 Nov 2010 10:50:03 -0500 Message-ID: <20101119155003.GA7145@infradead.org> References: <20101118134804.GN5618@dhcp231-156.rdu.redhat.com> <20101118141957.GK6178@parisc-linux.org> <20101118142918.GA18510@infradead.org> <1290100750.3041.72.camel@mulgrave.site> <1290168976.2570.45.camel@dolmen> <4CE68155.50705@teksavvy.com> <20101119140203.GC10039@thunk.org> <20101119141007.GB25488@infradead.org> <20101119153748.GE10039@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Ted Ts'o , Christoph Hellwig , Mark Lord , Steven Whitehouse , Lukas Czerner , James Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:39725 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751150Ab0KSPuH (ORCPT ); Fri, 19 Nov 2010 10:50:07 -0500 Content-Disposition: inline In-Reply-To: <20101119153748.GE10039@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Nov 19, 2010 at 10:37:48AM -0500, Ted Ts'o wrote: > I think the author of that slide deck was being a little hysterical. > In nearly all of these cases, if the file system is comptently > implemented (i.e., you don't do a trim on anything but a deleted file > block, and _only_ when you know the deleted is committed, and only the > filesystem --- not non-privileged users --- are allowed to use the > TRIM command), there's no issue. It's a huge issue for virtualization, where naive TRIM implementations can expose data deleted in one VM to others. It's also a huge issues for RAIDs as mentioned by you.