From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [PATCH v2 1/2] anon_inodes: allow external inode allocations Date: Wed, 9 Oct 2013 18:36:16 +0100 Message-ID: <20131009173616.GI13318@ZenIV.linux.org.uk> References: <1380713066-32519-1-git-send-email-dh.herrmann@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org To: David Herrmann Return-path: Content-Disposition: inline In-Reply-To: <1380713066-32519-1-git-send-email-dh.herrmann@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Oct 02, 2013 at 01:24:25PM +0200, David Herrmann wrote: > DRM core shares a single address_space across all inodes that belong to > the same DRM device. This allows efficient unmapping of user-space > mappings during buffer eviction. However, there is no easy way to get a > shared address_space for DRM devices during initialization. Therefore, we > currently delay this step until the first ->open() and save the given > inode for future use. > > This causes ugly delayed initialization throughout the DRM core. TTM > devices end up without a dev_mapping pointer and we have to carefully > respect any underlying filesystem implementation so we don't corrupt the > inode->i_mapping and inode->i_data fields. > > We can avoid this if we were allowed to allocate an anonymous inode for > each DRM device. We only have to set file->f_mapping during ->open() > and no longer need to adjust inode mappings. As fs/anon_inodes.c already > provides a minimal internal FS mount, we extend it to also provide > anonymous inodes for use in drivers like DRM. > > Signed-off-by: David Herrmann > Wanted-by: Daniel Vetter Told-to-stop-abusing-anon_inodes-by: Al Viro Note that anon_inode_getfile_private() is not going to survive - for exact same reasons. It's already removed in vfs.git#experimental, shortly in #for-next as well. Do NOT extend fs/anon_inodes.c; if you need a minimal internal fs mount, just do what fs/aio.c does in the same branch.