pagemap: add filemap_grab_folio()

Patch series "Convert to filemap_get_folios_tag()", v5.

This patch series replaces find_get_pages_range_tag() with
filemap_get_folios_tag().  This also allows the removal of multiple calls
to compound_head() throughout.

It also makes a good chunk of the straightforward conversions to folios,
and takes the opportunity to introduce a function that grabs a folio from
the pagecache.

This patch (of 23):

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().

Link: https://lkml.kernel.org/r/20230104211448.4804-1-vishal.moola@gmail.com
Link: https://lkml.kernel.org/r/20230104211448.4804-2-vishal.moola@gmail.com
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 29e1f9e..468183b 100644 (file)
--- 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,
 }
 
 /**
+ * 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
  * @offset: the page index