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

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