On Sat, Feb 11, 2017 at 9:59 AM, Logan Gunthorpe <[email protected]> wrote: > On 11/02/17 01:56 AM, Dan Williams wrote: >> >> When the device is unregistered it invalidates all existing mappings, >> but the driver may continue to service vm fault requests until the >> final put of the cdev. Until that time the fault handler needs to be >> able to check dax_dev->alive. Since the final cdev put is handled by >> the vfs I use the cdev's kobject to keep the struct dax_dev instance >> alive. > > > I'm just taking a wild stab at this, but would it not make sense to just > take a reference to the dax_dev device in dax_open and put it back it in > dax_release? (Or perhaps, in the open/close of the vm_ops.) That way the > structure won't be free'd until there are no users and alive will always be > accessible. > > It would also be a bit more clear as to what's going on because you are > actually making a reference in filp->private_data. >
Why, when the lifetime of the cdev is already correct? See commit ba09c01d2fa8 "dax: convert to the cdev api". I used to take explicit references like you suggest, but cdev made it cleaner.
