On 1/2/22 13:57, Matthew Wilcox (Oracle) wrote:
This is like folio_put(), but puts N references at once instead of
just one. It's like put_page_refs(), but does one atomic operation
instead of two, and is available to more than just gup.c.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/linux/mm.h | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index d8b7d7ed14dd..98a10412d581 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1237,6 +1237,26 @@ static inline void folio_put(struct folio *folio)
__put_page(&folio->page);
}
+/**
+ * folio_put_refs - Reduce the reference count on a folio.
+ * @folio: The folio.
+ * @refs: The number of references to reduce.
+ *
+ * If the folio's reference count reaches zero, the memory will be
+ * released back to the page allocator and may be used by another
+ * allocation immediately. Do not access the memory or the struct folio
+ * after calling folio_put_refs() unless you can be sure that these weren't
+ * the last references.
+ *
+ * Context: May be called in process or interrupt context, but not in NMI
+ * context. May be called while holding a spinlock.
The context documentation is a nice touch.
Come to think of it, there probably aren't many mm functions that *can* be called
in NMI context. :)
+ */
+static inline void folio_put_refs(struct folio *folio, int refs)
+{
+ if (folio_ref_sub_and_test(folio, refs))
+ __put_page(&folio->page);
+}
+
Looks good, and definitely better than the previous put_page_refs() approach.
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
thanks,
--
John Hubbard
NVIDIA
static inline void put_page(struct page *page)
{
struct folio *folio = page_folio(page);
