[PATCH 13/17] writeback: Factor writeback_get_folio() out of write_cache_pages()

[Christoph Hellwig <hch@xxxxxx>]

From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>

Move the loop for should-we-write-this-folio to its own function.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 mm/page-writeback.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index efcfffa800884d..9d37dd5e58ffb6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2442,6 +2442,25 @@ static bool should_writeback_folio(struct address_space *mapping,
 	return true;
 }
 
+static struct folio *writeback_get_folio(struct address_space *mapping,
+		struct writeback_control *wbc)
+{
+	struct folio *folio;
+
+	for (;;) {
+		folio = writeback_get_next(mapping, wbc);
+		if (!folio)
+			return NULL;
+		folio_lock(folio);
+		if (likely(should_writeback_folio(mapping, wbc, folio)))
+			break;
+		folio_unlock(folio);
+	}
+
+	trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
+	return folio;
+}
+
 static struct folio *writeback_iter_init(struct address_space *mapping,
 		struct writeback_control *wbc)
 {
@@ -2455,7 +2474,7 @@ static struct folio *writeback_iter_init(struct address_space *mapping,
 
 	wbc->err = 0;
 	folio_batch_init(&wbc->fbatch);
-	return writeback_get_next(mapping, wbc);
+	return writeback_get_folio(mapping, wbc);
 }
 
 /**
@@ -2498,17 +2517,9 @@ int write_cache_pages(struct address_space *mapping,
 
 	for (folio = writeback_iter_init(mapping, wbc);
 	     folio;
-	     folio = writeback_get_next(mapping, wbc)) {
+	     folio = writeback_get_folio(mapping, wbc)) {
 		unsigned long nr;
 
-		folio_lock(folio);
-		if (!should_writeback_folio(mapping, wbc, folio)) {
-			folio_unlock(folio);
-			continue;
-		}
-
-		trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
-
 		error = writepage(folio, wbc, data);
 		nr = folio_nr_pages(folio);
 		wbc->nr_to_write -= nr;
-- 
2.39.2