mm/writeback: Add folio_redirty_for_writepage()

Reimplement redirty_page_for_writepage() as a wrapper around
folio_redirty_for_writepage().  Account the number of pages in the
folio, add kernel-doc and move the prototype to writeback.h.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>

2 files changed, 27 insertions, 10 deletions

diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 39f5a8d963b1..c1e01bc36d32 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -95,3 +95,10 @@ bool clear_page_dirty_for_io(struct page *page)
 	return folio_clear_dirty_for_io(page_folio(page));
 }
 EXPORT_SYMBOL(clear_page_dirty_for_io);
+
+bool redirty_page_for_writepage(struct writeback_control *wbc,
+		struct page *page)
+{
+	return folio_redirty_for_writepage(wbc, page_folio(page));
+}
+EXPORT_SYMBOL(redirty_page_for_writepage);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7ef904363fb7..a0c35a9d8029 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2575,21 +2575,31 @@ void folio_account_redirty(struct folio *folio)
 }
 EXPORT_SYMBOL(folio_account_redirty);
 
-/*
- * When a writepage implementation decides that it doesn't want to write this
- * page for some reason, it should redirty the locked page via
- * redirty_page_for_writepage() and it should then unlock the page and return 0
+/**
+ * folio_redirty_for_writepage - Decline to write a dirty folio.
+ * @wbc: The writeback control.
+ * @folio: The folio.
+ *
+ * When a writepage implementation decides that it doesn't want to write
+ * @folio for some reason, it should call this function, unlock @folio and
+ * return 0.
+ *
+ * Return: True if we redirtied the folio.  False if someone else dirtied
+ * it first.
  */
-int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
+bool folio_redirty_for_writepage(struct writeback_control *wbc,
+		struct folio *folio)
 {
-	int ret;
+	bool ret;
+	long nr = folio_nr_pages(folio);
+
+	wbc->pages_skipped += nr;
+	ret = filemap_dirty_folio(folio->mapping, folio);
+	folio_account_redirty(folio);
 
-	wbc->pages_skipped++;
-	ret = __set_page_dirty_nobuffers(page);
-	account_page_redirty(page);
 	return ret;
 }
-EXPORT_SYMBOL(redirty_page_for_writepage);
+EXPORT_SYMBOL(folio_redirty_for_writepage);
 
 /**
  * folio_mark_dirty - Mark a folio as being modified.