From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
If this BUG() ever triggers, we'll have a dead system with no particular
information. Dumping the page will give us a fighting chance of debugging
the problem, and I think it's safe for us to just continue if we try
to clear the writeback bit on a page which already has the writeback
bit clear.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/filemap.c | 4 +---
mm/page-writeback.c | 5 +++++
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index b7c5d2402370..401b24d980ba 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1293,9 +1293,7 @@ void end_page_writeback(struct page *page)
rotate_reclaimable_page(page);
}
- if (!test_clear_page_writeback(page))
- BUG();
-
+ test_clear_page_writeback(page);
smp_mb__after_atomic();
wake_up_page(page, PG_writeback);
}
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7326b54ab728..ebaf0d8263a6 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2718,6 +2718,11 @@ int test_clear_page_writeback(struct page *page)
struct lruvec *lruvec;
int ret;
+ if (WARN_ON(!PageWriteback(page))) {
+ dump_page(page, "!writeback");
+ return false;
+ }
+
memcg = lock_page_memcg(page);
lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
if (mapping && mapping_use_writeback_tags(mapping)) {
--
2.25.1
