From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Subject: Re: [PATCH v2 01/12] fs-verity: add a documentation file Date: Mon, 17 Dec 2018 10:32:06 -0800 Message-ID: <20181217183205.GA141684@gmail.com> References: <20181101225230.88058-1-ebiggers@kernel.org> <20181101225230.88058-2-ebiggers@kernel.org> <20181212091406.GA31723@infradead.org> <20181212202609.GA193967@gmail.com> <20181213202249.GA3797@infradead.org> <20181214044802.GA681@sol.localdomain> <20181217164949.GA18626@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181217164949.GA18626@infradead.org> Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, "Theodore Y . Ts'o" , Jaegeuk Kim , Victor Hsieh , Chandan Rajendra , Linus Torvalds List-Id: linux-f2fs-devel.lists.sourceforge.net On Mon, Dec 17, 2018 at 08:49:49AM -0800, Christoph Hellwig wrote: > > > > Given that you alread use an ioctl as the interface what is the problem > > > of passing this data through the ioctl? > > > > Do you mean pass the verity metadata in a buffer? That cannot work in general, > > because it may be too large to fit into memory. > > Have a pointer in the ioctl and do get_user_pages on it. I don't see how that helps. The Merkle tree can still be too large to fit in memory. In the worst case, it might not even fit in the address space. And I don't see how get_user_pages() helps either over just copy_from_user(); what are you proposing to do with the pages after getting them, exactly? - Eric