[PATCH v9 59/96] mm/writeback: Add folio_mark_dirty

[Matthew Wilcox (Oracle)]

Reimplement set_page_dirty() as a wrapper around folio_mark_dirty().
There is no change to filesystems as they were already being called
with the compound_head of the page being marked dirty.  We avoid
several calls to compound_head(), both statically (through
using folio_dirty() instead of PageDirty() and dynamically by
calling folio_mapping() instead of page_mapping().

Also return bool instead of int to show the range of values actually
returned, and add kernel-doc.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
 include/linux/mm.h  |  3 ++-
 mm/folio-compat.c   |  6 ++++++
 mm/page-writeback.c | 28 +++++++++++++++-------------
 3 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 75279db82040..c72cecbfe00d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1998,7 +1998,8 @@ int redirty_page_for_writepage(struct writeback_control *wbc,
 void account_page_dirtied(struct page *page, struct address_space *mapping);
 void account_page_cleaned(struct page *page, struct address_space *mapping,
 			  struct bdi_writeback *wb);
-int set_page_dirty(struct page *page);
+bool folio_mark_dirty(struct folio *folio);
+bool set_page_dirty(struct page *page);
 int set_page_dirty_lock(struct page *page);
 void __cancel_dirty_page(struct page *page);
 static inline void cancel_dirty_page(struct page *page)
diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index d229b979b00d..a504ecf1d695 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -60,3 +60,9 @@ void mem_cgroup_uncharge(struct page *page)
 	folio_uncharge_cgroup(page_folio(page));
 }
 #endif
+
+bool set_page_dirty(struct page *page)
+{
+	return folio_mark_dirty(page_folio(page));
+}
+EXPORT_SYMBOL(set_page_dirty);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 4d36f4d3037f..d810841ed03a 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2543,8 +2543,9 @@ int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
 }
 EXPORT_SYMBOL(redirty_page_for_writepage);
 
-/*
- * Dirty a page.
+/**
+ * folio_mark_dirty - Mark a folio as being modified.
+ * @folio: The folio.
  *
  * For pages with a mapping this should be done under the page lock
  * for the benefit of asynchronous memory errors who prefer a consistent
@@ -2553,12 +2554,13 @@ EXPORT_SYMBOL(redirty_page_for_writepage);
  *
  * If the mapping doesn't provide a set_page_dirty a_op, then
  * just fall through and assume that it wants buffer_heads.
+ *
+ * Return: True if the folio was newly dirtied, false if it was already dirty.
  */
-int set_page_dirty(struct page *page)
+bool folio_mark_dirty(struct folio *folio)
 {
-	struct address_space *mapping = page_mapping(page);
+	struct address_space *mapping = folio_mapping(folio);
 
-	page = compound_head(page);
 	if (likely(mapping)) {
 		int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
 		/*
@@ -2571,21 +2573,21 @@ int set_page_dirty(struct page *page)
 		 * it will confuse readahead and make it restart the size rampup
 		 * process. But it's a trivial problem.
 		 */
-		if (PageReclaim(page))
-			ClearPageReclaim(page);
+		if (folio_reclaim(folio))
+			folio_clear_reclaim_flag(folio);
 #ifdef CONFIG_BLOCK
 		if (!spd)
 			spd = __set_page_dirty_buffers;
 #endif
-		return (*spd)(page);
+		return (*spd)(&folio->page);
 	}
-	if (!PageDirty(page)) {
-		if (!TestSetPageDirty(page))
-			return 1;
+	if (!folio_dirty(folio)) {
+		if (!folio_test_set_dirty_flag(folio))
+			return true;
 	}
-	return 0;
+	return false;
 }
-EXPORT_SYMBOL(set_page_dirty);
+EXPORT_SYMBOL(folio_mark_dirty);
 
 /*
  * set_page_dirty() is racy if the caller has no reference against
-- 
2.30.2