From: Fuad Tabba tabba@google.com
No functional change intended.
Signed-off-by: Fuad Tabba tabba@google.com Signed-off-by: Elliot Berman quic_eberman@quicinc.com --- include/linux/mm.h | 32 -------------------------------- include/linux/page_ref.h | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 32 insertions(+), 32 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h index 9849dfda44d43..fd0d10b08e7ac 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1580,38 +1580,6 @@ static inline void put_page(struct page *page) folio_put(folio); }
-/* - * GUP_PIN_COUNTING_BIAS, and the associated functions that use it, overload - * the page's refcount so that two separate items are tracked: the original page - * reference count, and also a new count of how many pin_user_pages() calls were - * made against the page. ("gup-pinned" is another term for the latter). - * - * With this scheme, pin_user_pages() becomes special: such pages are marked as - * distinct from normal pages. As such, the unpin_user_page() call (and its - * variants) must be used in order to release gup-pinned pages. - * - * Choice of value: - * - * By making GUP_PIN_COUNTING_BIAS a power of two, debugging of page reference - * counts with respect to pin_user_pages() and unpin_user_page() becomes - * simpler, due to the fact that adding an even power of two to the page - * refcount has the effect of using only the upper N bits, for the code that - * counts up using the bias value. This means that the lower bits are left for - * the exclusive use of the original code that increments and decrements by one - * (or at least, by much smaller values than the bias value). - * - * Of course, once the lower bits overflow into the upper bits (and this is - * OK, because subtraction recovers the original values), then visual inspection - * no longer suffices to directly view the separate counts. However, for normal - * applications that don't have huge page reference counts, this won't be an - * issue. - * - * Locking: the lockless algorithm described in folio_try_get_rcu() - * provides safe operation for get_user_pages(), page_mkclean() and - * other calls that race to set up page table entries. - */ -#define GUP_PIN_COUNTING_BIAS (1U << 10) - void unpin_user_page(struct page *page); void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, bool make_dirty); diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h index 1acf5bac7f503..e6aeaafb143ca 100644 --- a/include/linux/page_ref.h +++ b/include/linux/page_ref.h @@ -62,6 +62,38 @@ static inline void __page_ref_unfreeze(struct page *page, int v)
#endif
+/* + * GUP_PIN_COUNTING_BIAS, and the associated functions that use it, overload + * the page's refcount so that two separate items are tracked: the original page + * reference count, and also a new count of how many pin_user_pages() calls were + * made against the page. ("gup-pinned" is another term for the latter). + * + * With this scheme, pin_user_pages() becomes special: such pages are marked as + * distinct from normal pages. As such, the unpin_user_page() call (and its + * variants) must be used in order to release gup-pinned pages. + * + * Choice of value: + * + * By making GUP_PIN_COUNTING_BIAS a power of two, debugging of page reference + * counts with respect to pin_user_pages() and unpin_user_page() becomes + * simpler, due to the fact that adding an even power of two to the page + * refcount has the effect of using only the upper N bits, for the code that + * counts up using the bias value. This means that the lower bits are left for + * the exclusive use of the original code that increments and decrements by one + * (or at least, by much smaller values than the bias value). + * + * Of course, once the lower bits overflow into the upper bits (and this is + * OK, because subtraction recovers the original values), then visual inspection + * no longer suffices to directly view the separate counts. However, for normal + * applications that don't have huge page reference counts, this won't be an + * issue. + * + * Locking: the lockless algorithm described in folio_try_get_rcu() + * provides safe operation for get_user_pages(), page_mkclean() and + * other calls that race to set up page table entries. + */ +#define GUP_PIN_COUNTING_BIAS (1U << 10) + static inline int page_ref_count(const struct page *page) { return atomic_read(&page->_refcount);