Sean Paul <seanpaul@xxxxxxxxxxxx> 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!
--
-keith
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