Re: [PATCH v3 02/10] iov_iter: add iterator type for dmabuf maps

[Pavel Begunkov]

On 5/13/26 14:29, David Laight wrote:

On Wed, 13 May 2026 11:05:57 +0100
David Laight <david.laight.li...@gmail.com> wrote:

...

@@ -575,7 +575,8 @@ void iov_iter_advance(struct iov_iter *i, size_t size)
  {
        if (unlikely(i->count < size))
                size = i->count;
-       if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) {
+       if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i)) ||
+           unlikely(iov_iter_is_dmabuf_map(i))) {

Doesn't the extra check add more code to all the non-ubuf cases?
This could be fixed by either making iter_type a bitmask (with one bit set)

Not going to do that. It was specifically converted from bitmask
before, and the check optimisations like this were voiced back than.

or writing an iter_is_one_of(i, ITER_xxx, ITER_yyy) define that uses
'(1 << i->iter_type) & ((1 << ITER_xxx) | ...)'

This seems to DTRT:

#define _ITER_IS_ONE_OF(iter, t1, t2, t3, t4, t5, t6, t7, t8, ...) \
     ((1u << (iter)->iter_type) & ((1u << ITER_##t1) | (1u << ITER_##t2) | \
         (1u << ITER_##t3) | (1u << ITER_##t4) | (1u << ITER_##t5) | \
         (1u << ITER_##t6) | (1u << ITER_##t7) | (1u << ITER_##t8)))
#define ITER_IS_ONE_OF(iter, t, ...) \
     _ITER_IS_ONE_OF(iter, t, ## __VA_ARGS__, t, t, t, t, t, t, t)

We definitely don't want that, using them directly would've been
much cleaner.

if (get_type_mask(i) & (TYPE1 | TYPE2)) ...

--
Pavel Begunkov