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drm: use anon-inode instead of relying on cdevs

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DRM drivers share a common address_space across all character-devices of a
single DRM device. This allows simple buffer eviction and mapping-control.
However, DRM core currently waits for the first ->open() on any char-dev
to mark the underlying inode as backing inode of the device. This delayed
initialization causes ugly conditions all over the place:
  if (dev->dev_mapping)
    do_sth();

To avoid delayed initialization and to stop reusing the inode of the
char-dev, we allocate an anonymous inode for each DRM device and reset
filp->f_mapping to it on ->open().

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
This commit is contained in:
David Herrmann
2014-01-03 14:24:19 +01:00
parent 31bbe16f6d
commit 6796cb16c0
15 changed files with 44 additions and 54 deletions
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25
drivers/gpu/drm/drm_fops.c
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@@ -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);
/* share address_space across all char-devs of a single device */
filp->f_mapping = dev->anon_inode->i_mapping;
retcode = drm_open_helper(inode, filp, dev);
if (retcode)
@@ -121,12 +112,6 @@ 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;
}
@@ -434,7 +419,6 @@ 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);
@@ -549,9 +533,6 @@ 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);