Re: [PATCH v7 3/4] fs/proc/task_mmu: Implement IOCTL to get and/or the clear info about PTEs

[Peter Xu]

On Mon, Jan 23, 2023 at 05:18:13PM +0500, Muhammad Usama Anjum wrote:
> >> +	if (IS_GET_OP(p) && p->max_pages && (p->found_pages == p->max_pages))
> >> +		return -ENOSPC;
> > 
> > This is the function to test "whether the walker should walk the vma
> > specified".  This check should IIUC be meaningless because found_pages
> > doesn't boost during vma switching, while OTOH your pmd walker fn should do
> > proper check when increasing found_pages and return -ENOSPC properly when
> > the same condition met.  That should be enough, IMHO.
> This check is needed in case we want to abort the walk at once. We return
> negative value from here which aborts the walk. Returning negative value
> from pmd_entry doesn't abort the walk. So this check is needed in the
> test_walk.

Why?  What I see locally is (walk_pmd_range):

		if (ops->pmd_entry)
			err = ops->pmd_entry(pmd, addr, next, walk);
		if (err)
			break;

Thanks,

-- 
Peter Xu