[PATCH 16/17] mm: Make __end_folio_writeback() return void

Matthew Wilcox (Oracle)
2023-09-15T18:38:18Z

Rather than check the result of test-and-clear, just check that we have
the writeback bit set at the start. This wouldn't catch every case, but
it's good enough (and enables the next patch).

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
mm/filemap.c | 9 +++++++--
mm/internal.h | 2 +-
mm/page-writeback.c | 38 ++++++++++++++++----------------------
3 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 8262b85593be..53c0d71aae8e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1595,9 +1595,15 @@ EXPORT_SYMBOL(folio_wait_private_2_killable);
/**
* folio_end_writeback - End writeback against a folio.
* @folio: The folio.
+ *
+ * The folio must actually be under writeback.
+ *
+ * Context: May be called from process or interrupt context.
*/
void folio_end_writeback(struct folio *folio)
{
+ VM_BUG_ON_FOLIO(!folio_test_writeback(folio), folio);
+
/*
* folio_test_clear_reclaim() could be used here but it is an
* atomic operation and overkill in this particular case. Failing
@@ -1617,8 +1623,7 @@ void folio_end_writeback(struct folio *folio)
* reused before the folio_wake().
*/
folio_get(folio);
- if (!__folio_end_writeback(folio))
- BUG();
+ __folio_end_writeback(folio);

smp_mb__after_atomic();
folio_wake(folio, PG_writeback);
diff --git a/mm/internal.h b/mm/internal.h
index 30cf724ddbce..ccb08dd9b5ec 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -105,7 +105,7 @@ static inline void wake_throttle_isolated(pg_data_t *pgdat)

vm_fault_t do_swap_page(struct vm_fault *vmf);
void folio_rotate_reclaimable(struct folio *folio);
-bool __folio_end_writeback(struct folio *folio);
+void __folio_end_writeback(struct folio *folio);
void deactivate_file_folio(struct folio *folio);
void folio_activate(struct folio *folio);

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index b8d3d7040a50..410b53e888e3 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2940,11 +2940,10 @@ static void wb_inode_writeback_end(struct bdi_writeback *wb)
spin_unlock_irqrestore(&wb->work_lock, flags);
}

-bool __folio_end_writeback(struct folio *folio)
+void __folio_end_writeback(struct folio *folio)
{
long nr = folio_nr_pages(folio);
struct address_space *mapping = folio_mapping(folio);
- bool ret;

folio_memcg_lock(folio);
if (mapping && mapping_use_writeback_tags(mapping)) {
@@ -2953,19 +2952,16 @@ bool __folio_end_writeback(struct folio *folio)
unsigned long flags;

xa_lock_irqsave(&mapping->i_pages, flags);
- ret = folio_test_clear_writeback(folio);
- if (ret) {
- __xa_clear_mark(&mapping->i_pages, folio_index(folio),
- PAGECACHE_TAG_WRITEBACK);
- if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
- struct bdi_writeback *wb = inode_to_wb(inode);
-
- wb_stat_mod(wb, WB_WRITEBACK, -nr);
- __wb_writeout_add(wb, nr);
- if (!mapping_tagged(mapping,
- PAGECACHE_TAG_WRITEBACK))
- wb_inode_writeback_end(wb);
- }
+ folio_test_clear_writeback(folio);
+ __xa_clear_mark(&mapping->i_pages, folio_index(folio),
+ PAGECACHE_TAG_WRITEBACK);
+ if (bdi->capabilities & BDI_CAP_WRITEBACK_ACCT) {
+ struct bdi_writeback *wb = inode_to_wb(inode);
+
+ wb_stat_mod(wb, WB_WRITEBACK, -nr);
+ __wb_writeout_add(wb, nr);
+ if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK))
+ wb_inode_writeback_end(wb);
}

if (mapping->host && !mapping_tagged(mapping,
@@ -2974,15 +2970,13 @@ bool __folio_end_writeback(struct folio *folio)

xa_unlock_irqrestore(&mapping->i_pages, flags);
} else {
- ret = folio_test_clear_writeback(folio);
- }
- if (ret) {
- lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr);
- zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
- node_stat_mod_folio(folio, NR_WRITTEN, nr);
+ folio_test_clear_writeback(folio);
}
+
+ lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr);
+ zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
+ node_stat_mod_folio(folio, NR_WRITTEN, nr);
folio_memcg_unlock(folio);
- return ret;
}

bool __folio_start_writeback(struct folio *folio, bool keep_write)
--
2.40.1