[PATCH 0/2] Anonymous Inode Allocations

[David Herrmann]

Hi

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 (but kept simple, TTM can be converted later).

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 an 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)
So I didn't spent much time on that approach.

Cheers
David

David Herrmann (2):
  anon_inodes: allow external inode allocations
  DRM: use anon_inode instead of delayed inode init

 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        |  4 ++--
 drivers/gpu/drm/nouveau/nouveau_gem.c  |  2 +-
 drivers/gpu/drm/omapdrm/omap_gem.c     |  7 ++++---
 drivers/gpu/drm/qxl/qxl_object.c       |  2 +-
 drivers/gpu/drm/qxl/qxl_ttm.c          |  2 +-
 drivers/gpu/drm/radeon/radeon_object.c |  2 +-
 drivers/gpu/drm/radeon/radeon_ttm.c    |  2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    |  2 +-
 fs/anon_inodes.c                       | 36 +++++++++++++++++++++++++++-------
 include/drm/drmP.h                     |  2 +-
 include/linux/anon_inodes.h            |  1 +
 14 files changed, 57 insertions(+), 42 deletions(-)

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1.8.3.2