[PATCH 12/19] writeback: Factor writeback_iter_init() out of write_cache_pages()

Christoph Hellwig
2024-01-25T08:58:53Z

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

Make it return the first folio in the batch so that we can use it
in a typical for() pattern.

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>
---
mm/page-writeback.c | 39 ++++++++++++++++++++-------------------
1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 432bb42d0829d1..ae9f659e6796ac 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2446,6 +2446,22 @@ static struct folio *writeback_get_folio(struct address_space *mapping,
return folio;
}

+static struct folio *writeback_iter_init(struct address_space *mapping,
+ struct writeback_control *wbc)
+{
+ if (wbc->range_cyclic)
+ wbc->index = mapping->writeback_index; /* prev offset */
+ else
+ wbc->index = wbc->range_start >> PAGE_SHIFT;
+
+ if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
+ tag_pages_for_writeback(mapping, wbc->index, wbc_end(wbc));
+
+ wbc->err = 0;
+ folio_batch_init(&wbc->fbatch);
+ return writeback_get_folio(mapping, wbc);
+}
+
/**
* write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
* @mapping: address space structure to write
@@ -2481,29 +2497,14 @@ int write_cache_pages(struct address_space *mapping,
struct writeback_control *wbc, writepage_t writepage,
void *data)
{
+ struct folio *folio;
int error;
- pgoff_t end; /* Inclusive */

- if (wbc->range_cyclic) {
- wbc->index = mapping->writeback_index; /* prev offset */
- end = -1;
- } else {
- wbc->index = wbc->range_start >> PAGE_SHIFT;
- end = wbc->range_end >> PAGE_SHIFT;
- }
- if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
- tag_pages_for_writeback(mapping, wbc->index, end);
-
- folio_batch_init(&wbc->fbatch);
- wbc->err = 0;
-
- for (;;) {
- struct folio *folio = writeback_get_folio(mapping, wbc);
+ for (folio = writeback_iter_init(mapping, wbc);
+ folio;
+ folio = writeback_get_folio(mapping, wbc)) {
unsigned long nr;

- if (!folio)
- break;
-
folio_lock(folio);
if (!folio_prepare_writeback(mapping, wbc, folio)) {
folio_unlock(folio);
--
2.39.2