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SubjectRe: [PATCH 34/49] gma500: the GEM and GTT code is device independant
Hi Alan,

On Tue, 5 Jul 2011, Alan Cox wrote:
> From: Alan Cox <alan@linux.intel.com>
>
> Rename the gem and gtt files accordingly.
>
> Signed-off-by: Alan Cox <alan@linux.intel.com>

This caught my eye, and I realize that I'm in the process of
sabotaging your work, or vice versa: sorry!

> +
> + for (i = 0; i < pages; i++) {
> + /* FIXME: review flags later */
> + p = read_cache_page_gfp(mapping, i,
> + __GFP_COLD | GFP_KERNEL);
...
> -
> - for (i = 0; i < pages; i++) {
> - /* FIXME: review flags later */
> - p = read_cache_page_gfp(mapping, i,
> - __GFP_COLD | GFP_KERNEL);

I've been eliminating drm/i915's calls to read_cache_page_gfp(),
while you've been adding them to staging/gma500. It still works in
3.0-rc, but if my further changes go through from mmotm to 3.1-rc,
then read_cache_page_gfp() on a shmem/tmpfs file will crash on the
lack of a readpage method (we could easily make it error instead
of crash, but you'd probably prefer something that actually works).

As example, below is the patch where I updated drm/i915 to be ready
for the changeover. They set __GFP_RECLAIMABLE on the mapping because
they've got a way to discard unpinned object pages when memory is tight;
and sometimes add in __GFP_NORETRY|__GFP_NOWARN when allocating.
I'm guessing you'd just want to use shmem_read_mapping_page() throughout,
after initializing mapping with the appropriate flags (GFP_HIGHUSER_MOVABLE
is fs/inode.c's default: maybe your pages aren't easily movable and you'd
better say GFP_HIGHUSER, or maybe you have reason to need GFP_KERNEL).

Hugh

commit 5949eac4d9b5bf936c12cb7ec3a09084c1326834
Author: Hugh Dickins <hughd@google.com>
Date: Mon Jun 27 16:18:18 2011 -0700

drm/i915: use shmem_read_mapping_page

Soon tmpfs will stop supporting ->readpage and read_cache_page_gfp(): once
"tmpfs: add shmem_read_mapping_page_gfp" has been applied, this patch can
be applied to ease the transition.

Make i915_gem_object_get_pages_gtt() use shmem_read_mapping_page_gfp() in
the one place it's needed; elsewhere use shmem_read_mapping_page(), with
the mapping's gfp_mask properly initialized.

Forget about __GFP_COLD: since tmpfs initializes its pages with memset,
asking for a cold page is counter-productive.

Include linux/shmem_fs.h also in drm_gem.c: with shmem_file_setup() now
declared there too, we shall remove the prototype from linux/mm.h later.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Keith Packard <keithp@keithp.com>
Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 74e4ff5..4012fe4 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -34,6 +34,7 @@
#include <linux/module.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
+#include <linux/shmem_fs.h>
#include "drmP.h"

/** @file drm_gem.c
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c6389de..fa560ce 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -31,6 +31,7 @@
#include "i915_drv.h"
#include "i915_trace.h"
#include "intel_drv.h"
+#include <linux/shmem_fs.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/pci.h>
@@ -359,8 +360,7 @@ i915_gem_shmem_pread_fast(struct drm_device *dev,
if ((page_offset + remain) > PAGE_SIZE)
page_length = PAGE_SIZE - page_offset;

- page = read_cache_page_gfp(mapping, offset >> PAGE_SHIFT,
- GFP_HIGHUSER | __GFP_RECLAIMABLE);
+ page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
if (IS_ERR(page))
return PTR_ERR(page);

@@ -463,8 +463,7 @@ i915_gem_shmem_pread_slow(struct drm_device *dev,
if ((data_page_offset + page_length) > PAGE_SIZE)
page_length = PAGE_SIZE - data_page_offset;

- page = read_cache_page_gfp(mapping, offset >> PAGE_SHIFT,
- GFP_HIGHUSER | __GFP_RECLAIMABLE);
+ page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto out;
@@ -797,8 +796,7 @@ i915_gem_shmem_pwrite_fast(struct drm_device *dev,
if ((page_offset + remain) > PAGE_SIZE)
page_length = PAGE_SIZE - page_offset;

- page = read_cache_page_gfp(mapping, offset >> PAGE_SHIFT,
- GFP_HIGHUSER | __GFP_RECLAIMABLE);
+ page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
if (IS_ERR(page))
return PTR_ERR(page);

@@ -907,8 +905,7 @@ i915_gem_shmem_pwrite_slow(struct drm_device *dev,
if ((data_page_offset + page_length) > PAGE_SIZE)
page_length = PAGE_SIZE - data_page_offset;

- page = read_cache_page_gfp(mapping, offset >> PAGE_SHIFT,
- GFP_HIGHUSER | __GFP_RECLAIMABLE);
+ page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT);
if (IS_ERR(page)) {
ret = PTR_ERR(page);
goto out;
@@ -1558,12 +1555,10 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj,

inode = obj->base.filp->f_path.dentry->d_inode;
mapping = inode->i_mapping;
+ gfpmask |= mapping_gfp_mask(mapping);
+
for (i = 0; i < page_count; i++) {
- page = read_cache_page_gfp(mapping, i,
- GFP_HIGHUSER |
- __GFP_COLD |
- __GFP_RECLAIMABLE |
- gfpmask);
+ page = shmem_read_mapping_page_gfp(mapping, i, gfpmask);
if (IS_ERR(page))
goto err_pages;

@@ -3565,6 +3560,7 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
{
struct drm_i915_private *dev_priv = dev->dev_private;
struct drm_i915_gem_object *obj;
+ struct address_space *mapping;

obj = kzalloc(sizeof(*obj), GFP_KERNEL);
if (obj == NULL)
@@ -3575,6 +3571,9 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
return NULL;
}

+ mapping = obj->base.filp->f_path.dentry->d_inode->i_mapping;
+ mapping_set_gfp_mask(mapping, GFP_HIGHUSER | __GFP_RECLAIMABLE);
+
i915_gem_info_add_obj(dev_priv, size);

obj->base.write_domain = I915_GEM_DOMAIN_CPU;
@@ -3950,8 +3949,7 @@ void i915_gem_detach_phys_object(struct drm_device *dev,

page_count = obj->base.size / PAGE_SIZE;
for (i = 0; i < page_count; i++) {
- struct page *page = read_cache_page_gfp(mapping, i,
- GFP_HIGHUSER | __GFP_RECLAIMABLE);
+ struct page *page = shmem_read_mapping_page(mapping, i);
if (!IS_ERR(page)) {
char *dst = kmap_atomic(page);
memcpy(dst, vaddr + i*PAGE_SIZE, PAGE_SIZE);
@@ -4012,8 +4010,7 @@ i915_gem_attach_phys_object(struct drm_device *dev,
struct page *page;
char *dst, *src;

- page = read_cache_page_gfp(mapping, i,
- GFP_HIGHUSER | __GFP_RECLAIMABLE);
+ page = shmem_read_mapping_page(mapping, i);
if (IS_ERR(page))
return PTR_ERR(page);



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