[PATCH v12 1/7] mm: move clearing the dropbehind flag of a found folio into a helper

[Mike Snitzer <snitzer@kernel.org>]

Move the code in __filemap_get_folio_mpol() that clears PG_dropbehind
on a folio found by a cached lookup, and takes the folio off
WB_DONTCACHE_DIRTY, into filemap_clear_dropbehind().  No functional
change.  The next patch changes the helper.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
 mm/filemap.c | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index b04be64a5069f..437113addbddf 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1956,6 +1956,24 @@ void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
 	return folio;
 }
 
+/* Clear the dropbehind flag of a folio that a cached lookup found. */
+static void filemap_clear_dropbehind(struct address_space *mapping,
+				     struct folio *folio)
+{
+	if (!folio_test_clear_dropbehind(folio))
+		return;
+	if (folio_test_dirty(folio) && mapping_can_writeback(mapping)) {
+		struct inode *inode = mapping->host;
+		struct bdi_writeback *wb;
+		struct wb_lock_cookie cookie = {};
+		long nr = folio_nr_pages(folio);
+
+		wb = unlocked_inode_to_wb_begin(inode, &cookie);
+		wb_stat_mod(wb, WB_DONTCACHE_DIRTY, -nr);
+		unlocked_inode_to_wb_end(inode, &cookie);
+	}
+}
+
 /**
  * __filemap_get_folio_mpol - Find and get a reference to a folio.
  * @mapping: The address_space to search.
@@ -2087,19 +2105,8 @@ struct folio *__filemap_get_folio_mpol(struct address_space *mapping,
 	if (!folio)
 		return ERR_PTR(-ENOENT);
 	/* not an uncached lookup, clear uncached if set */
-	if (!(fgp_flags & FGP_DONTCACHE) && folio_test_clear_dropbehind(folio)) {
-		if (folio_test_dirty(folio) &&
-		    mapping_can_writeback(mapping)) {
-			struct inode *inode = mapping->host;
-			struct bdi_writeback *wb;
-			struct wb_lock_cookie cookie = {};
-			long nr = folio_nr_pages(folio);
-
-			wb = unlocked_inode_to_wb_begin(inode, &cookie);
-			wb_stat_mod(wb, WB_DONTCACHE_DIRTY, -nr);
-			unlocked_inode_to_wb_end(inode, &cookie);
-		}
-	}
+	if (!(fgp_flags & FGP_DONTCACHE))
+		filemap_clear_dropbehind(mapping, folio);
 	return folio;
 }
 EXPORT_SYMBOL(__filemap_get_folio_mpol);
-- 
2.52.0