Re: [PATCH v4 2/2] mm/hmm/test: add self tests for HMM

[Ralph Campbell]

On 11/12/19 7:25 AM, Christoph Hellwig wrote:
> Shouldn't this go into mm/ instead? It certainly doesn't seem
> like a library.

I was following the convention for the other vm test kernel modules.
I see a couple of modules in mm/ but I don't have a personal
preference for where to place it.

Andrew, do you have a preference?

> > +static int dmirror_bounce_copy_from(struct dmirror_bounce *bounce,
> > +				    unsigned long addr)
> > +{
> > +	unsigned long end = addr + bounce->size;
> > +	char __user *uptr = (void __user *)addr;
> > +	void *ptr = bounce->ptr;
> > +
> > +	for (; addr < end; addr += PAGE_SIZE, ptr += PAGE_SIZE,
> > +					      uptr += PAGE_SIZE) {
> > +		int ret;
> > +
> > +		ret = copy_from_user(ptr, uptr, PAGE_SIZE);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	return 0;
> > +}
>
> Why does this iterate in page sized chunks?  I don't remember a page
> size limit on copy_{from,to}_user.

Good point. I'll fix that.

> > +static int dmirror_invalidate_range_start(struct mmu_notifier *mn,
> > +				const struct mmu_notifier_range *update)
> > +{
> > +	struct dmirror *dmirror = container_of(mn, struct dmirror, notifier);
> > +
> > +	if (mmu_notifier_range_blockable(update))
> > +		mutex_lock(&dmirror->mutex);
> > +	else if (!mutex_trylock(&dmirror->mutex))
> > +		return -EAGAIN;
> > +
> > +	dmirror_do_update(dmirror, update->start, update->end);
> > +	mutex_unlock(&dmirror->mutex);
> > +	return 0;
> > +}
>
> Can we adopts this to Jasons new interval tree invalidate?

Well, it would mean registering for the whole process address space.
I'll give it a try.

> > +static int dmirror_fops_open(struct inode *inode, struct file *filp)
> > +{
> > +	struct cdev *cdev = inode->i_cdev;
> > +	struct dmirror_device *mdevice;
> > +	struct dmirror *dmirror;
> > +
> > +	/* No exclusive opens. */
> > +	if (filp->f_flags & O_EXCL)
> > +		return -EINVAL;
>
> Device files usually just ignore O_EXCL, I don't see why this one
> would be any different.

OK, I'll remove that test.

> > +	mdevice = container_of(cdev, struct dmirror_device, cdevice);
> > +	dmirror = dmirror_new(mdevice);
> > +	if (!dmirror)
> > +		return -ENOMEM;
> > +
> > +	/* Only the first open registers the address space. */
> > +	mutex_lock(&mdevice->devmem_lock);
> > +	if (filp->private_data)
> > +		goto err_busy;
> > +	filp->private_data = dmirror;
> > +	mutex_unlock(&mdevice->devmem_lock);
>
> ->open is only called for the first open of a given file structure..
>
> > +static int dmirror_fops_release(struct inode *inode, struct file *filp)
> > +{
> > +	struct dmirror *dmirror = filp->private_data;
> > +
> > +	if (!dmirror)
> > +		return 0;
>
> This can't happen if your ->open never returns 0 without setting the
> private data.
>
> > +	filp->private_data = NULL;
>
> The file is feed afterwards, no need to clear the private data.

OK, I'll clean that up.