[PATCH 15/19] writeback: Add for_each_writeback_folio()

Christoph Hellwig
2024-01-25T08:59:04Z

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

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>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
---
include/linux/writeback.h | 10 ++++++++++
mm/page-writeback.c | 8 +++-----
2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index a091817a5dba55..2416da933440e2 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -367,6 +367,16 @@ 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);

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index d5815237fbec29..aca0f43021a20c 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2458,7 +2458,7 @@ 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)
@@ -2474,7 +2474,7 @@ 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);
@@ -2552,9 +2552,7 @@ 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;
--
2.39.2