+/**
- pin_user_pages_fast() - pin user pages in memory without taking locks
- Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See
- get_user_pages_fast() for documentation on the function arguments, because
- the arguments here are identical.
- FOLL_PIN means that the pages must be released via put_user_page(). Please
- see Documentation/vm/pin_user_pages.rst for further details.
- This is intended for Case 1 (DIO) in Documentation/vm/pin_user_pages.rst. It
- is NOT intended for Case 2 (RDMA: long-term pins).
- */
+int pin_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages)+{
- /* FOLL_GET and FOLL_PIN are mutually exclusive. */
- if (WARN_ON_ONCE(gup_flags & FOLL_GET))
return -EINVAL;- gup_flags |= FOLL_PIN;
- return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
+} +EXPORT_SYMBOL_GPL(pin_user_pages_fast);
I was somewhat wondering about the number of functions you add here. So we have:
pin_user_pages() pin_user_pages_fast() pin_user_pages_remote()
and then longterm variants:
pin_longterm_pages() pin_longterm_pages_fast() pin_longterm_pages_remote()
and obviously we have gup like: get_user_pages() get_user_pages_fast() get_user_pages_remote() ... and some other gup variants ...
I think we really should have pin_* vs get_* variants as they are very different in terms of guarantees and after conversion, any use of get_* variant in non-mm code should be closely scrutinized. OTOH pin_longterm_* don't look *that* useful to me and just using pin_* instead with FOLL_LONGTERM flag would look OK to me and somewhat reduce the number of functions which is already large enough? What do people think? I don't feel too strongly about this but wanted to bring this up.
I'm a bit concerned with the function explosion myself. I think what you suggest is a happy medium. So I'd be ok with that.
Ira