GFP_TEMPORARY was introduced by commit e12ba74d8ff3 ("Group short-lived
and reclaimable kernel allocations") along with __GFP_RECLAIMABLE.  It's
primary motivation was to allow users to tell that an allocation is
short lived and so the allocator can try to place such allocations close
together and prevent long term fragmentation.  As much as this sounds
like a reasonable semantic it becomes much less clear when to use the
highlevel GFP_TEMPORARY allocation flag.  How long is temporary? Can the
context holding that memory sleep? Can it take locks? It seems there is
no good answer for those questions.

The current implementation of GFP_TEMPORARY is basically GFP_KERNEL |
__GFP_RECLAIMABLE which in itself is tricky because basically none of
the existing caller provide a way to reclaim the allocated memory.  So
this is rather misleading and hard to evaluate for any benefits.

I have checked some random users and none of them has added the flag
with a specific justification.  I suspect most of them just copied from
other existing users and others just thought it might be a good idea to
use without any measuring.  This suggests that GFP_TEMPORARY just
motivates for cargo cult usage without any reasoning.

I believe that our gfp flags are quite complex already and especially
those with highlevel semantic should be clearly defined to prevent from
confusion and abuse.  Therefore I propose dropping GFP_TEMPORARY and
replace all existing users to simply use GFP_KERNEL.  Please note that
SLAB users with shrinkers will still get __GFP_RECLAIMABLE heuristic and
so they will be placed properly for memory fragmentation prevention.

I can see reasons we might want some gfp flag to reflect shorterm
allocations but I propose starting from a clear semantic definition and
only then add users with proper justification.

This was been brought up before LSF this year by Matthew [1] and it
turned out that GFP_TEMPORARY really doesn't have a clear semantic.  It
seems to be a heuristic without any measured advantage for most (if not
all) its current users.  The follow up discussion has revealed that
opinions on what might be temporary allocation differ a lot between
developers.  So rather than trying to tweak existing users into a
semantic which they haven't expected I propose to simply remove the flag
and start from scratch if we really need a semantic for short term
allocations.

[1] http://lkml.kernel.org/r/20170118054945.GD18349@bombadil.infradead.org

[akpm@linux-foundation.org: fix typo]
[akpm@linux-foundation.org: coding-style fixes]
[sfr@canb.auug.org.au: drm/i915: fix up]
  Link: http://lkml.kernel.org/r/20170816144703.378d4f4d@canb.auug.org.au
Link: http://lkml.kernel.org/r/20170728091904.14627-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Neil Brown <neilb@suse.de>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Updates for 4.14..  I have some further patches from Jordan to add
multiple priority levels and pre-emption, but those will probably be
for 4.15 to give me time for the mesa parts.

* tag 'drm-msm-next-2017-08-22' of git://people.freedesktop.org/~robclark/linux:
  drm/msm/mdp5: mark runtime_pm functions as __maybe_unused
  drm/msm: remove unused variable
  drm/msm/mdp5: make helper function static
  drm/msm: make msm_framebuffer_init() static
  drm/msm: add helper to allocate stolen fb
  drm/msm: don't track fbdev's gem object separately
  drm/msm: add modeset module param
  drm/msm/mdp5: add tracking for clk enable-count
  drm/msm: remove unused define
  drm/msm: Add a helper function for in-kernel buffer allocations
  drm/msm: Attach the GPU MMU when it is created
  drm/msm: Add A5XX hardware fault detection
  drm/msm: Remove uneeded platform dev members
  drm/msm/mdp5: Set up runtime PM for MDSS
  drm/msm/mdp5: Write to SMP registers even if allocations don't change
  drm/msm/mdp5: Don't use mode_set helper funcs for encoders and CRTCs
  drm/msm/dsi: Implement RPM suspend/resume callbacks
  drm/msm/dsi: Set up runtime PM for DSI
  drm/msm/hdmi: Set up runtime PM for HDMI
  drm/msm/mdp5: Use runtime PM get/put API instead of toggling clocks

When CONFIG_PM is disabled, we get harmless warnings about unused
functions:

drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c:1025:12: error: 'mdp5_runtime_resume' defined but not used [-Werror=unused-function]
 static int mdp5_runtime_resume(struct device *dev)
            ^~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/msm/mdp/mdp5/mdp5_kms.c:1015:12: error: 'mdp5_runtime_suspend' defined but not used [-Werror=unused-function]
 static int mdp5_runtime_suspend(struct device *dev)
            ^~~~~~~~~~~~~~~~~~~~

This marks both functions as __maybe_unused so the compiler
can drop them silently.

Fixes: d68fe15b1878 ("drm/msm/mdp5: Use runtime PM get/put API instead of toggling clocks")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rob Clark <robdclark@gmail.com>

A cleanup left behind an unused variable that we have to remove
in order to avoid this harmless warning:

drivers/gpu/drm/msm/adreno/a5xx_gpu.c: In function 'a5xx_zap_shader_init':
drivers/gpu/drm/msm/adreno/a5xx_gpu.c:493:19: error: unused variable 'a5xx_gpu' [-Werror=unused-variable]

Fixes: 8d6f08272b6f ("drm/msm: Remove uneeded platform dev members")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rob Clark <robdclark@gmail.com>

Not needed outside of mdp5_crtc.c.

Signed-off-by: Rob Clark <robdclark@gmail.com>

Only needed in msm_fb.c so don't export it.

Signed-off-by: Rob Clark <robdclark@gmail.com>

We'll later want to re-use this for state-readback when bootloader
enables display, so that we can create an fb for the initial
plane->state->fb.

Signed-off-by: Rob Clark <robdclark@gmail.com>

The drm_framebuffer is refcnt'd these days and will unref the underlying
bo as needed.  So we can simplify a little.

Signed-off-by: Rob Clark <robdclark@gmail.com>

At least for debugging it is nice to have an easy way to force the
driver not to load.

Signed-off-by: Rob Clark <robdclark@gmail.com>

Accessing registers for an unclocked block is an insta-reboot on
snapdragon devices.  So add a bit of logic to track the enable_count so
we can WARN_ON() unclocked register writes.  This makes it much easier
to track down mistakes.

Signed-off-by: Rob Clark <robdclark@gmail.com>