linux-kernel - [PATCH v2 0/4] Anonymous Inode Allocations

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Message-Id: <1376415739-11685-1-git-send-email-dh.herrmann@gmail.com>
Date:	Tue, 13 Aug 2013 19:42:15 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	dri-devel@...ts.freedesktop.org
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Dave Airlie <airlied@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	David Herrmann <dh.herrmann@...il.com>
Subject: [PATCH v2 0/4] Anonymous Inode Allocations

Hi

This is v2 of my anon_inodes allocation series. I would really like some
comments on #1 (and maybe #2) from VFS maintainers/developers so we can continue
with this work. Patches 1 and 2 are unchanged, I added 3 and 4 to clean up DRM
delayed initializations based on the new anon_inode.

This implements anon_inodes_new() to create anonymous inodes. Patch #1
describes the changes to anon_inodes.c and why DRM could make great use of this.
Patch #2 converts DRM core to use anon_inodes_new() instead of delayed
dev_mapping initialization. Patches #3 and #4 simplify the various driver bits
to drop unused code paths.

The idea is to get an anonymous backing inode for DRM devices without waiting
for the first char-dev inode. We use it to unmap userspace mappings via
unmap_mapping_range() if we have to evict buffers if GTT runs short or if the FW
framebuffers are destroyed.
We need the inode only once the first user-space mapping was created. But the
delayed initialization causes an ugly code base and keeps inodes of char-devs
around just to preserve the address_space.

We actually only need the address_space, but mm core requires a corresponding
file* and FS core requires mapping->host to be set (although I am not sure
whether we can hit those paths with char-devs). So I went with the whole
anonymous inode approach.

If anyone has an idea how to use an embedded "struct address_space" inside of
"drm_device" and set "dev_mapping->host" to the shared anon_inode_inode, I'd be
happy to implement it. However, I didn't succeed and I am actually not sure that
separate "struct address_space" are actually supported. For instance, DRM core
uses code like:
  container_of(dev_mapping, struct inode, i_data)
which would break in this case.

Cheers
David

David Herrmann (4):
  anon_inodes: allow external inode allocations
  DRM: use anon_inode instead of delayed inode init
  drm: init TTM dev_mapping in ttm_bo_device_init()
  drm/omap: remove useless if() in evict_entry()

 drivers/gpu/drm/ast/ast_ttm.c          |  4 +++-
 drivers/gpu/drm/cirrus/cirrus_ttm.c    |  4 +++-
 drivers/gpu/drm/drm_drv.c              |  1 -
 drivers/gpu/drm/drm_fops.c             | 24 +++--------------------
 drivers/gpu/drm/drm_stub.c             | 12 +++++++++++-
 drivers/gpu/drm/i915/i915_gem.c        |  3 ++-
 drivers/gpu/drm/mgag200/mgag200_ttm.c  |  4 +++-
 drivers/gpu/drm/nouveau/nouveau_gem.c  |  2 --
 drivers/gpu/drm/nouveau/nouveau_ttm.c  |  4 +++-
 drivers/gpu/drm/omapdrm/omap_gem.c     | 33 +++++++++++++++----------------
 drivers/gpu/drm/qxl/qxl_object.c       |  2 --
 drivers/gpu/drm/qxl/qxl_ttm.c          |  6 +++---
 drivers/gpu/drm/radeon/radeon_object.c |  1 -
 drivers/gpu/drm/radeon/radeon_ttm.c    |  5 +++--
 drivers/gpu/drm/ttm/ttm_bo.c           |  3 ++-
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    |  5 +++--
 fs/anon_inodes.c                       | 36 +++++++++++++++++++++++++++-------
 include/drm/drmP.h                     |  2 +-
 include/drm/drm_vma_manager.h          |  6 +++---
 include/drm/ttm/ttm_bo_driver.h        |  2 ++
 include/linux/anon_inodes.h            |  1 +
 21 files changed, 91 insertions(+), 69 deletions(-)

-- 
1.8.3.4

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