On 8/8/21 6:39 PM, Matthew Wilcox wrote:

On Sun, Aug 08, 2021 at 04:50:16PM -0700, John Hubbard wrote:

quoted

@@ -103,8 +103,14 @@ static inline struct page *try_get_compound_head(struct page *page, int refs)
   * same time. (That's true throughout the get_user_pages*() and
   * pin_user_pages*() APIs.) Cases:
   *
- *    FOLL_GET: page's refcount will be incremented by 1.
- *    FOLL_PIN: page's refcount will be incremented by GUP_PIN_COUNTING_BIAS.
+ *    FOLL_GET: page's refcount will be incremented by refs.

I think this would read more clearly if it said @refs (throughout).

OK, will change that for v2.

quoted

+ *
+ *    FOLL_PIN on compound pages that are > two pages long: page's refcount will
+ *        be incremented by refs, and page[2].hpage_pinned_refcount will be
+ *        incremented by refs * GUP_PIN_COUNTING_BIAS.
+ *
+ *    FOLL_PIN on normal pages, or compound pages that are two pages long:
+ *        page's refcount will be incremented by refs * GUP_PIN_COUNTING_BIAS.
   *
   * Return: head page (with refcount appropriately incremented) for success, or
   * NULL upon failure. If neither FOLL_GET nor FOLL_PIN was set, that's

Did you run 'make htmldocs' and see how it renders?  I haven't looked,
but this might work better as an rst list?

Hadn't occurred to me, due to my own incorrect mental separation between
comment kernel docs, and rst formatting ("rst == Documentation/"). I'll give it a try.

thanks,
-- 
John Hubbard
NVIDIA