On Wed, 13 May 2026 11:05:57 +0100 David Laight david.laight.linux@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) 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)
int foo(void *); int f(struct iov_iter *i) { return ITER_IS_ONE_OF(i, UBUF, KVEC) ? foo(i) : 0; }
See https://godbolt.org/z/sMz93zah1
Pasting ITER_ on the front ensures the values are constants of the right type. OTOH it makes it harder to search for uses of each type. You could paste _ITER_ on the front, elsewhere define _ITER_ITER_UVEC to be ITER_UVEC (etc), and require the caller use the full name.
-- David