Re: [PATCH v10 3/6] fs/proc/task_mmu: Implement IOCTL to get and/or the clear info about PTEs

[Muhammad Usama Anjum]

Hi Cyrill,

Thank you for your time and review.

On 2/9/23 3:22 AM, Cyrill Gorcunov wrote:
> On Thu, Feb 02, 2023 at 04:29:12PM +0500, Muhammad Usama Anjum wrote:
> ...
> Hi Muhammad! I'm really sorry for not commenting this code, just out of time and i
> fear cant look with precise care at least for some time, hopefully other CRIU guys
> pick it up. Anyway, here a few comment from a glance.
> 
>> +
>> +static inline int pagemap_scan_output(bool wt, bool file, bool pres, bool swap,
>> +				      struct pagemap_scan_private *p, unsigned long addr,
>> +				      unsigned int len)
>> +{
> 
> This is a big function and usually it's a flag to not declare it as "inline" until
> there very serious reson to.
I'll remove all these inline in next revision.

> 
>> +	unsigned long bitmap, cur = PAGEMAP_SCAN_BITMAP(wt, file, pres, swap);
>> +	bool cpy = true;
>> +	struct page_region *prev = &p->prev;
>> +
>> +	if (HAS_NO_SPACE(p))
>> +		return -ENOSPC;
>> +
>> +	if (p->max_pages && p->found_pages + len >= p->max_pages)
>> +		len = p->max_pages - p->found_pages;
>> +	if (!len)
>> +		return -EINVAL;
>> +
>> +	if (p->required_mask)
>> +		cpy = ((p->required_mask & cur) == p->required_mask);
>> +	if (cpy && p->anyof_mask)
>> +		cpy = (p->anyof_mask & cur);
>> +	if (cpy && p->excluded_mask)
>> +		cpy = !(p->excluded_mask & cur);
>> +	bitmap = cur & p->return_mask;
>> +	if (cpy && bitmap) {
> 
> You can exit early here simply
> 
> 	if (!cpy || !bitmap)
> 		return 0;
I'm avoiding an extra return here.

> 
> saving one tab for the code below.
> 
>> +		if ((prev->len) && (prev->bitmap == bitmap) &&
>> +		    (prev->start + prev->len * PAGE_SIZE == addr)) {
>> +			prev->len += len;
>> +			p->found_pages += len;
>> +		} else if (p->vec_index < p->vec_len) {
>> +			if (prev->len) {
>> +				memcpy(&p->vec[p->vec_index], prev, sizeof(struct page_region));
>> +				p->vec_index++;
>> +			}
>> +			prev->start = addr;
>> +			prev->len = len;
>> +			prev->bitmap = bitmap;
>> +			p->found_pages += len;
>> +		} else {
>> +			return -ENOSPC;
>> +		}
>> +	}
>> +	return 0;
>> +}
>> +
>> +static inline int export_prev_to_out(struct pagemap_scan_private *p, struct page_region __user *vec,
>> +				     unsigned long *vec_index)
>> +{
> 
> No need for inline either.
> 
>> +	struct page_region *prev = &p->prev;
>> +
>> +	if (prev->len) {
>> +		if (copy_to_user(&vec[*vec_index], prev, sizeof(struct page_region)))
>> +			return -EFAULT;
>> +		p->vec_index++;
>> +		(*vec_index)++;
>> +		prev->len = 0;
>> +	}
>> +	return 0;
>> +}
>> +
>> +static inline int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
>> +					 unsigned long end, struct mm_walk *walk)
>> +{
> 
> Same, no need for inline. I've a few comments more in my mind will try to
> collect them tomorrow.
Your review would be much appreciated.

-- 
BR,
Muhammad Usama Anjum