Re: [PATCH v3 02/15] userfaultfd: introduce struct mfill_state

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 1 Apr 2026 10:36:03 +0300 Mike Rapoport <rppt@kernel.org> wrote:

> Here's a fixup (it causes a conflict in patch 4 though).
> Andrew, I can send v4 if you prefer.

Looks pretty simple.  "userfaultfd: introduce mfill_get_vma() and
mfill_put_vma()" now leaves things like this:

retry:
	err = mfill_get_vma(&state);
	if (err)
		goto out;
	state.vma = dst_vma;

	/*
	 * If this is a HUGETLB vma, pass off to appropriate routine
	 */
	if (is_vm_hugetlb_page(state.vma))
		return mfill_atomic_hugetlb(ctx, state.vma, dst_start,
					    src_start, len, flags);

	while (state.src_addr < src_start + len) {
		VM_WARN_ON_ONCE(state.dst_addr >= dst_start + len);

		err = mfill_establish_pmd(&state);
		if (err)
			break;

		/*
		 * For shmem mappings, khugepaged is allowed to remove page
		 * tables under us; pte_offset_map_lock() will deal with that.
		 */

		err = mfill_atomic_pte(&state);
		cond_resched();

		if (unlikely(err == -ENOENT)) {
			void *kaddr;

			mfill_put_vma(&state);
			VM_WARN_ON_ONCE(!state.folio);

			kaddr = kmap_local_folio(state.folio, 0);
			err = copy_from_user(kaddr,
					     (const void __user *)state.src_addr,
					     PAGE_SIZE);
			kunmap_local(kaddr);
			if (unlikely(err)) {
				err = -EFAULT;
				goto out;
			}
			flush_dcache_folio(state.folio);
			goto retry;
		} else
			VM_WARN_ON_ONCE(state.folio);

		if (!err) {
			state.dst_addr += PAGE_SIZE;
			state.src_addr += PAGE_SIZE;
			copied += PAGE_SIZE;

			if (fatal_signal_pending(current))
				err = -EINTR;
		}
		if (err)
			break;
	}