@@ -2521,6 +2521,7 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
struct folio **folios, unsigned int max_folios,
pgoff_t *offset);
+void folio_split_user_page_pin(struct folio *folio, unsigned long npages);
int get_user_pages_fast(unsigned long start, int nr_pages,
unsigned int gup_flags, struct page **pages);
@@ -3733,3 +3733,23 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
return ret;
}
EXPORT_SYMBOL_GPL(memfd_pin_folios);
+
+/**
+ * folio_split_user_page_pin() - split the pin on a high order folio
+ * @folio: the folio to split
+ * @npages: The new number of pages the folio pin reference should hold
+ *
+ * Given a high order folio that is already pinned, adjust the reference
+ * count to allow unpin_user_page_range() and related to be called on a
+ * the folio. npages is the number of pages that will be passed to a
+ * future unpin_user_page_range().
+ */
+void folio_split_user_page_pin(struct folio *folio, unsigned long npages)
+{
+ if (!folio_test_large(folio) || is_huge_zero_folio(folio) ||
+ npages == 1)
+ return;
+ atomic_add(npages - 1, &folio->_refcount);
+ atomic_add(npages - 1, &folio->_pincount);
+}
+EXPORT_SYMBOL_GPL(folio_split_user_page_pin);
Export a function that repins a high-order folio at small-page granularity. This allows any range of small pages within the folio to be unpinned later. For example, pages pinned via memfd_pin_folios and modified by folio_split_user_page_pin could be unpinned via unpin_user_page(s). Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Steve Sistare <steven.sistare@oracle.com> --- In V2 this has been renamed from repin_folio_unhugely, but is otherwise unchanged from V1. --- --- include/linux/mm.h | 1 + mm/gup.c | 20 ++++++++++++++++++++ 2 files changed, 21 insertions(+)