[PATCH 2/2] DRM: use anon_inode instead of delayed inode init

From: David Herrmann
Date: Wed Oct 02 2013 - 07:25:33 EST

Instead of delaying inode initialization until first ->open(), we can use
an anonymous inode. This avoids modifying FS internal inode fields and
provides us a private address_space right during initialization.

Delayed TTM dev_mapping initialization is currently left untouched to keep
this simple. But we could now safely provide the address_space during
ttm_bo_device_init() instead of delaying until first buffer ->mmap().

Note that this also fixes several bugs:
- We currently call iput(container_of(..dev_mapping..)) before
drm_lastclose(), but we reset dev_mapping to zero at the end of
drm_lastclose(). This fails if dev_mapping points to an address_space
other than the current inode and the char-dev got already removed.
- We also drop dev_mapping during any drm_lastclose() call. So if
user-space still has VMAs to our buffers, we will be unable to unmap
them if the next ->firstopen() is on another inode. dev_mapping will
then point to a new address_space and we leak mappings that we no
longer control.
- We ignore inode->i_mapping completely. It is unlikely that a FS uses it
to overwrite inode->i_data for char-devs, but it definitely doesn't
look very nice to ignore it silently.

Tested with nouveau on x86_64.

Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/gpu/drm/ast/ast_ttm.c | 2 +-
drivers/gpu/drm/cirrus/cirrus_ttm.c | 2 +-
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 | 2 +-
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 +-
include/drm/drmP.h | 2 +-
15 files changed, 30 insertions(+), 37 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_ttm.c b/drivers/gpu/drm/ast/ast_ttm.c
index 32aecb3..74eed74 100644
--- a/drivers/gpu/drm/ast/ast_ttm.c
+++ b/drivers/gpu/drm/ast/ast_ttm.c
@@ -324,7 +324,7 @@ int ast_bo_create(struct drm_device *dev, int size, int align,
}

astbo->bo.bdev = &ast->ttm.bdev;
- astbo->bo.bdev->dev_mapping = dev->dev_mapping;
+ astbo->bo.bdev->dev_mapping = dev->anon_inode->i_mapping;

ast_ttm_placement(astbo, TTM_PL_FLAG_VRAM | TTM_PL_FLAG_SYSTEM);

diff --git a/drivers/gpu/drm/cirrus/cirrus_ttm.c b/drivers/gpu/drm/cirrus/cirrus_ttm.c
index 75becde..abd401d 100644
--- a/drivers/gpu/drm/cirrus/cirrus_ttm.c
+++ b/drivers/gpu/drm/cirrus/cirrus_ttm.c
@@ -329,7 +329,7 @@ int cirrus_bo_create(struct drm_device *dev, int size, int align,
}

cirrusbo->bo.bdev = &cirrus->ttm.bdev;
- cirrusbo->bo.bdev->dev_mapping = dev->dev_mapping;
+ cirrusbo->bo.bdev->dev_mapping = dev->anon_inode->i_mapping;

cirrus_ttm_placement(cirrusbo, TTM_PL_FLAG_VRAM | TTM_PL_FLAG_SYSTEM);

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index e572dd2..7d91ddb 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -231,7 +231,6 @@ int drm_lastclose(struct drm_device * dev)

drm_legacy_dma_takedown(dev);

- dev->dev_mapping = NULL;
mutex_unlock(&dev->struct_mutex);

drm_legacy_dev_reinit(dev);
diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
index 3f84277..41a57c8 100644
--- a/drivers/gpu/drm/drm_fops.c
+++ b/drivers/gpu/drm/drm_fops.c
@@ -84,8 +84,6 @@ int drm_open(struct inode *inode, struct file *filp)
struct drm_minor *minor;
int retcode = 0;
int need_setup = 0;
- struct address_space *old_mapping;
- struct address_space *old_imapping;

minor = idr_find(&drm_minors_idr, minor_id);
if (!minor)
@@ -99,16 +97,9 @@ int drm_open(struct inode *inode, struct file *filp)

if (!dev->open_count++)
need_setup = 1;
- mutex_lock(&dev->struct_mutex);
- old_imapping = inode->i_mapping;
- old_mapping = dev->dev_mapping;
- if (old_mapping == NULL)
- dev->dev_mapping = &inode->i_data;
- /* ihold ensures nobody can remove inode with our i_data */
- ihold(container_of(dev->dev_mapping, struct inode, i_data));
- inode->i_mapping = dev->dev_mapping;
- filp->f_mapping = dev->dev_mapping;
- mutex_unlock(&dev->struct_mutex);
+
+ /* set address_space for shared mappings */
+ filp->f_mapping = dev->anon_inode->i_mapping;

retcode = drm_open_helper(inode, filp, dev);
if (retcode)
@@ -122,12 +113,6 @@ int drm_open(struct inode *inode, struct file *filp)
return 0;

err_undo:
- mutex_lock(&dev->struct_mutex);
- filp->f_mapping = old_imapping;
- inode->i_mapping = old_imapping;
- iput(container_of(dev->dev_mapping, struct inode, i_data));
- dev->dev_mapping = old_mapping;
- mutex_unlock(&dev->struct_mutex);
dev->open_count--;
return retcode;
}
@@ -492,9 +477,6 @@ int drm_release(struct inode *inode, struct file *filp)
}
}

- BUG_ON(dev->dev_mapping == NULL);
- iput(container_of(dev->dev_mapping, struct inode, i_data));
-
/* drop the reference held my the file priv */
if (file_priv->master)
drm_master_put(&file_priv->master);
diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 39d8645..0d9efa2 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -31,6 +31,7 @@
* DEALINGS IN THE SOFTWARE.
*/

+#include <linux/anon_inodes.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
@@ -271,8 +272,14 @@ int drm_fill_in_dev(struct drm_device *dev,
mutex_init(&dev->struct_mutex);
mutex_init(&dev->ctxlist_mutex);

+ /* create private address_space on anon inode */
+ dev->anon_inode = anon_inode_new();
+ if (IS_ERR(dev->anon_inode))
+ return PTR_ERR(dev->anon_inode);
+
if (drm_ht_create(&dev->map_hash, 12)) {
- return -ENOMEM;
+ retcode = -ENOMEM;
+ goto err_inode;
}

/* the DRM has 6 basic counters */
@@ -313,6 +320,8 @@ int drm_fill_in_dev(struct drm_device *dev,

error_out_unreg:
drm_lastclose(dev);
+err_inode:
+ iput(dev->anon_inode);
return retcode;
}
EXPORT_SYMBOL(drm_fill_in_dev);
@@ -465,6 +474,7 @@ void drm_put_dev(struct drm_device *dev)

drm_put_minor(&dev->primary);

+ iput(dev->anon_inode);
list_del(&dev->driver_item);
kfree(dev->devname);
kfree(dev);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 36c4ad9..fc571cc 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1435,7 +1435,8 @@ i915_gem_release_mmap(struct drm_i915_gem_object *obj)
if (!obj->fault_mappable)
return;

- drm_vma_node_unmap(&obj->base.vma_node, obj->base.dev->dev_mapping);
+ drm_vma_node_unmap(&obj->base.vma_node,
+ obj->base.dev->anon_inode->i_mapping);
obj->fault_mappable = false;
}

diff --git a/drivers/gpu/drm/mgag200/mgag200_ttm.c b/drivers/gpu/drm/mgag200/mgag200_ttm.c
index 07b192f..bb2a1cb 100644
--- a/drivers/gpu/drm/mgag200/mgag200_ttm.c
+++ b/drivers/gpu/drm/mgag200/mgag200_ttm.c
@@ -324,7 +324,7 @@ int mgag200_bo_create(struct drm_device *dev, int size, int align,
}

mgabo->bo.bdev = &mdev->ttm.bdev;
- mgabo->bo.bdev->dev_mapping = dev->dev_mapping;
+ mgabo->bo.bdev->dev_mapping = dev->anon_inode->i_mapping;

mgag200_ttm_placement(mgabo, TTM_PL_FLAG_VRAM | TTM_PL_FLAG_SYSTEM);

diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index f32b712..4572758 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -237,7 +237,7 @@ nouveau_gem_ioctl_new(struct drm_device *dev, void *data,
struct nouveau_bo *nvbo = NULL;
int ret = 0;

- drm->ttm.bdev.dev_mapping = drm->dev->dev_mapping;
+ drm->ttm.bdev.dev_mapping = drm->dev->anon_inode->i_mapping;

if (!pfb->memtype_valid(pfb, req->info.tile_flags)) {
NV_ERROR(cli, "bad page flags: 0x%08x\n", req->info.tile_flags);
diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index 533f6eb..7115c23 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -153,7 +153,7 @@ static struct {
static void evict_entry(struct drm_gem_object *obj,
enum tiler_fmt fmt, struct usergart_entry *entry)
{
- if (obj->dev->dev_mapping) {
+ if (obj->dev->anon_inode->i_mapping) {
struct omap_gem_object *omap_obj = to_omap_bo(obj);
int n = usergart[fmt].height;
size_t size = PAGE_SIZE * n;
@@ -164,12 +164,13 @@ static void evict_entry(struct drm_gem_object *obj,
int i;
/* if stride > than PAGE_SIZE then sparse mapping: */
for (i = n; i > 0; i--) {
- unmap_mapping_range(obj->dev->dev_mapping,
+ unmap_mapping_range(obj->dev->anon_inode->i_mapping,
off, PAGE_SIZE, 1);
off += PAGE_SIZE * m;
}
} else {
- unmap_mapping_range(obj->dev->dev_mapping, off, size, 1);
+ unmap_mapping_range(obj->dev->anon_inode->i_mapping,
+ off, size, 1);
}
}

diff --git a/drivers/gpu/drm/qxl/qxl_object.c b/drivers/gpu/drm/qxl/qxl_object.c
index 8691c76..f3204c9 100644
--- a/drivers/gpu/drm/qxl/qxl_object.c
+++ b/drivers/gpu/drm/qxl/qxl_object.c
@@ -83,7 +83,7 @@ int qxl_bo_create(struct qxl_device *qdev,
int r;

if (unlikely(qdev->mman.bdev.dev_mapping == NULL))
- qdev->mman.bdev.dev_mapping = qdev->ddev->dev_mapping;
+ qdev->mman.bdev.dev_mapping = qdev->ddev->anon_inode->i_mapping;
if (kernel)
type = ttm_bo_type_kernel;
else
diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
index 037786d..7d7ff7a 100644
--- a/drivers/gpu/drm/qxl/qxl_ttm.c
+++ b/drivers/gpu/drm/qxl/qxl_ttm.c
@@ -517,7 +517,7 @@ int qxl_ttm_init(struct qxl_device *qdev)
DRM_INFO("qxl: %luM of IO pages memory ready (VRAM domain)\n",
((unsigned)num_io_pages * PAGE_SIZE) / (1024 * 1024));
if (unlikely(qdev->mman.bdev.dev_mapping == NULL))
- qdev->mman.bdev.dev_mapping = qdev->ddev->dev_mapping;
+ qdev->mman.bdev.dev_mapping = qdev->ddev->anon_inode->i_mapping;
r = qxl_ttm_debugfs_init(qdev);
if (r) {
DRM_ERROR("Failed to init debugfs\n");
diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index c0fa4aa..0900b36 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -120,7 +120,7 @@ int radeon_bo_create(struct radeon_device *rdev,

size = ALIGN(size, PAGE_SIZE);

- rdev->mman.bdev.dev_mapping = rdev->ddev->dev_mapping;
+ rdev->mman.bdev.dev_mapping = rdev->ddev->anon_inode->i_mapping;
if (kernel) {
type = ttm_bo_type_kernel;
} else if (sg) {
diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 71245d6..ab1b8ff 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -737,7 +737,7 @@ int radeon_ttm_init(struct radeon_device *rdev)
}
DRM_INFO("radeon: %uM of GTT memory ready.\n",
(unsigned)(rdev->mc.gtt_size / (1024 * 1024)));
- rdev->mman.bdev.dev_mapping = rdev->ddev->dev_mapping;
+ rdev->mman.bdev.dev_mapping = rdev->ddev->anon_inode->i_mapping;

r = radeon_ttm_debugfs_init(rdev);
if (r) {
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 1a90f0a..d5a20c4 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -762,7 +762,7 @@ static int vmw_driver_open(struct drm_device *dev, struct drm_file *file_priv)
goto out_no_tfile;

file_priv->driver_priv = vmw_fp;
- dev_priv->bdev.dev_mapping = dev->dev_mapping;
+ dev_priv->bdev.dev_mapping = dev->anon_inode->i_mapping;

return 0;

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index b46fb45..073772a 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1197,7 +1197,7 @@ struct drm_device {
unsigned int num_crtcs; /**< Number of CRTCs on this device */
void *dev_private; /**< device private data */
void *mm_private;
- struct address_space *dev_mapping;
+ struct inode *anon_inode;
struct drm_sigdata sigdata; /**< For block_all_signals */
sigset_t sigmask;

--
1.8.4

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