Sean Paul seanpaul@chromium.org writes:
nit: space before ,
Thanks.
- /* Clone the lessor file to create a new file for us */
- DRM_DEBUG_LEASE("Allocating lease file\n");
- path_get(&lessor_file->f_path);
Please forgive the stupid question, but where is this reference given up?
That's not a stupid question, it's a very subtle one which took me quite a while to sort out. Here's path_get:
void path_get(const struct path *path) { mntget(path->mnt); dget(path->dentry); }
So, getting a reference on a 'path' actually gets a reference on two of the things it points to.
alloc_file is passed the path and doesn't take an additional reference on either of these fields, presumably because the normal path has the caller taking a reference while looking up the object and handing that reference off to alloc_file. In our case, we're creating a new file that refers to the same path as an existing one, so we need another reference.
When the file is finally freed in __fput, the two references are dropped at the end of the function:
static void __fput(struct file *file) { struct dentry *dentry = file->f_path.dentry; struct vfsmount *mnt = file->f_path.mnt;
...
dput(dentry); mntput(mnt); }
This was probably the twistiest part of creating a lease. All of the DRM stuff was trivial; getting the core kernel object reference counts right was a pain.
- if (lessee->lessor == NULL)
/* owner can use all objects */object_idr = &lessee->dev->mode_config.crtc_idr;What about other types of objects?
If I understand your question correctly, the answer is that 'crtc_idr' is misnamed -- it holds all of the mode setting objects.
Thanks for your review, let me know if you have more questions!