From 949c4a34afacfe800fc442afac117aba15284962 Mon Sep 17 00:00:00 2001 From: Ilija Hadzic Date: Tue, 15 May 2012 16:40:10 -0400 Subject: drm: track dev_mapping in more robust and flexible way Setting dev_mapping (pointer to the address_space structure used for memory mappings) to the address_space of the first opener's inode and then failing if other openers come in through a different inode has a few restrictions that are eliminated by this patch. If we already have valid dev_mapping and we spot an opener with different i_node, we force its i_mapping pointer to the already established address_space structure (first opener's inode). This will make all mappings from drm device hang off the same address_space object. Some benefits (things that now work and didn't work before) of this patch are: * user space can mknod and use any number of device nodes and they will all work fine as long as the major device number is that of the drm module. * user space can even remove the first opener's device nodes and mknod the new one and the applications and windowing system will still work. * GPU drivers can safely assume that dev->dev_mapping is correct address_space and just blindly copy it into their (private) bdev.dev_mapping For reference, some discussion that lead to this patch can be found here: http://lists.freedesktop.org/archives/dri-devel/2012-April/022283.html Signed-off-by: Ilija Hadzic Signed-off-by: Dave Airlie --- drivers/gpu/drm/drm_fops.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'drivers/gpu/drm/drm_fops.c') diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c index d25a61739a7b..5062eec673f1 100644 --- a/drivers/gpu/drm/drm_fops.c +++ b/drivers/gpu/drm/drm_fops.c @@ -140,12 +140,12 @@ int drm_open(struct inode *inode, struct file *filp) } if (!retcode) { mutex_lock(&dev->struct_mutex); - if (minor->type == DRM_MINOR_LEGACY) { - if (dev->dev_mapping == NULL) - dev->dev_mapping = inode->i_mapping; - else if (dev->dev_mapping != inode->i_mapping) - retcode = -ENODEV; - } + if (dev->dev_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); } @@ -509,6 +509,9 @@ 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 */ drm_master_put(&file_priv->master); file_priv->is_master = 0; -- cgit v1.2.3