writeback: Add for_each_writeback_folio()

Wrap up the iterator with a nice bit of syntactic sugar.  Now the
caller doesn't need to know about wbc->err and can just return error,
not knowing that the iterator took care of storing errors correctly.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 7dd050b40e4b40dc2d11a7eb59dc2ca4320b6c85..84d5306ef0450cd9b85aae7c81dcb367c379d651 100644 (file)
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -369,14 +369,22 @@ int balance_dirty_pages_ratelimited_flags(struct address_space *mapping,
 
 bool wb_over_bg_thresh(struct bdi_writeback *wb);
 
+struct folio *writeback_iter_init(struct address_space *mapping,
+               struct writeback_control *wbc);
+struct folio *writeback_iter_next(struct address_space *mapping,
+               struct writeback_control *wbc, struct folio *folio, int error);
+
+#define for_each_writeback_folio(mapping, wbc, folio, error)           \
+       for (folio = writeback_iter_init(mapping, wbc);                 \
+            folio || ((error = wbc->err), false);                      \
+            folio = writeback_iter_next(mapping, wbc, folio, error))
+
 typedef int (*writepage_t)(struct folio *folio, struct writeback_control *wbc,
                                void *data);
-
-void tag_pages_for_writeback(struct address_space *mapping,
-                            pgoff_t start, pgoff_t end);
 int write_cache_pages(struct address_space *mapping,
                      struct writeback_control *wbc, writepage_t writepage,
                      void *data);
+
 int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
 void writeback_set_ratelimit(void);
 void tag_pages_for_writeback(struct address_space *mapping,

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 16cc414202117dbd44a789b569b6990162a9b40c..7ee4deb3eef0f70ca033aacf4e7e510eb266f45f 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2450,7 +2450,7 @@ static struct folio *writeback_get_folio(struct address_space *mapping,
        return folio;
 }
 
-static struct folio *writeback_iter_init(struct address_space *mapping,
+struct folio *writeback_iter_init(struct address_space *mapping,
                struct writeback_control *wbc)
 {
        if (wbc->range_cyclic) {
@@ -2472,7 +2472,7 @@ static struct folio *writeback_iter_init(struct address_space *mapping,
        return writeback_get_folio(mapping, wbc);
 }
 
-static struct folio *writeback_iter_next(struct address_space *mapping,
+struct folio *writeback_iter_next(struct address_space *mapping,
                struct writeback_control *wbc, struct folio *folio, int error)
 {
        unsigned long nr = folio_nr_pages(folio);
@@ -2551,13 +2551,10 @@ int write_cache_pages(struct address_space *mapping,
        struct folio *folio;
        int error;
 
-       for (folio = writeback_iter_init(mapping, wbc);
-            folio;
-            folio = writeback_iter_next(mapping, wbc, folio, error)) {
+       for_each_writeback_folio(mapping, wbc, folio, error)
                error = writepage(folio, wbc, data);
-       }
 
-       return wbc->err;
+       return error;
 }
 EXPORT_SYMBOL(write_cache_pages);