[PATCH v4 3/5] folio: Add replacements for page_endio()

[David Howells]

Add three functions to replace page_endio():

 (1) folio_end_read().  End a read to a folio.

 (2) folio_end_write().  End a write from a folio.

 (3) folio_endio().  A switcher that does one or the other of the above.

Change page_endio() to just call folio_endio().  Note that the parameter
order is switched so that the folio_endio() stub doesn't have to shuffle
the params around, but can rather just test and jump.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Tested-by: Jeff Layton <jlayton@xxxxxxxxxx>
Tested-by: Dominique Martinet <asmadeus@xxxxxxxxxxxxx>
Tested-by: kafs-testing@xxxxxxxxxxxx
Link: https://lore.kernel.org/r/1088663.1635955216@xxxxxxxxxxxxxxxxxxxxxx/
---

 include/linux/pagemap.h |    9 ++++++-
 mm/filemap.c            |   64 ++++++++++++++++++++++++++++++++---------------
 2 files changed, 51 insertions(+), 22 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 1a0c646eb6ff..fd90544bb3e4 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -895,7 +895,14 @@ static inline int __must_check write_one_page(struct page *page)
 int __set_page_dirty_nobuffers(struct page *page);
 int __set_page_dirty_no_writeback(struct page *page);
 
-void page_endio(struct page *page, bool is_write, int err);
+void folio_end_read(struct folio *folio, int err);
+void folio_end_write(struct folio *folio, int err);
+void folio_endio(struct folio *folio, int err, bool is_write);
+
+static inline void page_endio(struct page *page, bool is_write, int err)
+{
+	folio_endio(page_folio(page), err, is_write);
+}
 
 void folio_end_private_2(struct folio *folio);
 void folio_wait_private_2(struct folio *folio);
diff --git a/mm/filemap.c b/mm/filemap.c
index daa0e23a6ee6..841e87b2d6ab 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1612,33 +1612,55 @@ void folio_end_writeback(struct folio *folio)
 }
 EXPORT_SYMBOL(folio_end_writeback);
 
-/*
- * After completing I/O on a page, call this routine to update the page
- * flags appropriately
+/**
+ * folio_end_read - Update the state of a folio after a read
+ * @folio: The folio to update
+ * @err: The error code (or 0) to apply
  */
-void page_endio(struct page *page, bool is_write, int err)
+void folio_end_read(struct folio *folio, int err)
 {
-	if (!is_write) {
-		if (!err) {
-			SetPageUptodate(page);
-		} else {
-			ClearPageUptodate(page);
-			SetPageError(page);
-		}
-		unlock_page(page);
+	if (!err) {
+		folio_mark_uptodate(folio);
 	} else {
-		if (err) {
-			struct address_space *mapping;
+		folio_clear_uptodate(folio);
+		folio_set_error(folio);
+	}
+	folio_unlock(folio);
+}
+EXPORT_SYMBOL_GPL(folio_end_read);
 
-			SetPageError(page);
-			mapping = page_mapping(page);
-			if (mapping)
-				mapping_set_error(mapping, err);
-		}
-		end_page_writeback(page);
+/**
+ * folio_end_write - Update the state of a folio after a write
+ * @folio: The folio to update
+ * @err: The error code (or 0) to apply
+ */
+void folio_end_write(struct folio *folio, int err)
+{
+	if (err) {
+		struct address_space *mapping = folio_mapping(folio);
+
+		folio_set_error(folio);
+		if (mapping)
+			mapping_set_error(mapping, err);
 	}
+	folio_end_writeback(folio);
+}
+EXPORT_SYMBOL_GPL(folio_end_write);
+
+/**
+ * folio_endio - Update the state of a folio after a read or write
+ * @folio: The folio to update
+ * @err: The error code (or 0) to apply
+ * @is_write: True if this was a write
+ */
+void folio_endio(struct folio *folio, int err, bool is_write)
+{
+	if (is_write)
+		folio_end_write(folio, err);
+	else
+		folio_end_read(folio, err);
 }
-EXPORT_SYMBOL_GPL(page_endio);
+EXPORT_SYMBOL_GPL(folio_endio);
 
 /**
  * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.