Re: [PATCH v7 1/1] kasan: Avoid sleepable page allocation from atomic context

[Alexander Gordeev <agordeev@linux.ibm.com>]

On Tue, May 13, 2025 at 12:33:35AM +0900, Harry Yoo wrote:
> Thanks for the update, but I don't think nr_populated is sufficient
> here. If nr_populated in the last iteration is smaller than its value
> in any previous iteration, it could lead to a memory leak.
> 
> That's why I suggested (PAGE_SIZE / sizeof(data.pages[0])).
> ...but on second thought maybe touching the whole array is not
> efficient either.

Yes, I did not like it and wanted to limit the number of pages,
but did not realize that using nr_populated still could produce
leaks. In addition I could simply do:

	max_populted = max(max_populted, nr_populated);
	...
	free_pages_bulk(data.pages, max_populated);

> If this ends up making things complicated probably we should just
> merge v6 instead (v6 looks good)? micro-optimizing vmalloc shadow memory
> population doesn't seem worth it if it comes at the cost of complexity :)

v6 is okay, except that in v7 I use break instead of return:

	ret = apply_to_page_range(...);
	if (ret)
		break;

and as result can call the final:

	free_page((unsigned long)data.pages);

Frankly, I do not have strong opinion.

> -- 
> Cheers,
> Harry / Hyeonggon

Thanks!