[PATCH v2 0/4] Anonymous Inode Allocations

From: David Herrmann
Date: Tue Aug 13 2013 - 13:43:18 EST


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.


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(-)


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