[PATCH v4 01/23] pagemap: Add filemap_grab_folio()

["Vishal Moola (Oracle)" <vishal.moola@gmail.com>]

Add function filemap_grab_folio() to grab a folio from the page cache.
This function is meant to serve as a folio replacement for
grab_cache_page, and is used to facilitate the removal of
find_get_pages_range_tag().

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/pagemap.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index bbccb4044222..74d87e37a142 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -547,6 +547,26 @@ static inline struct folio *filemap_lock_folio(struct address_space *mapping,
 	return __filemap_get_folio(mapping, index, FGP_LOCK, 0);
 }
 
+/**
+ * filemap_grab_folio - grab a folio from the page cache
+ * @mapping: The address space to search
+ * @index: The page index
+ *
+ * Looks up the page cache entry at @mapping & @index. If no folio is found,
+ * a new folio is created. The folio is locked, marked as accessed, and
+ * returned.
+ *
+ * Return: A found or created folio. NULL if no folio is found and failed to
+ * create a folio.
+ */
+static inline struct folio *filemap_grab_folio(struct address_space *mapping,
+					pgoff_t index)
+{
+	return __filemap_get_folio(mapping, index,
+			FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
+			mapping_gfp_mask(mapping));
+}
+
 /**
  * find_get_page - find and get a page reference
  * @mapping: the address_space to search
-- 
2.38.1