[Devel] [PATCH] tcache: Repeat invalidation in tcache_invalidate_node_pages()

[Kirill Tkhai]

When there are more than 2 users of a page,  __tcache_page_tree_delete()
fails to freeze it. We skip it and never try to freeze the page again.

In this case the page remains not invalidated, and tcache_node->nr_pages
never decremented. Later, we catch WARN_ON() reporting about this.

The patch fixes the problem. In case of we failed to invalidate a page,
we remember that, and return to such pages after others are invalidated.

https://jira.sw.ru/browse/PSBM-78354

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 mm/tcache.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/mm/tcache.c b/mm/tcache.c
index d1a2c53e11a..cbc50d4b8bc 100644
--- a/mm/tcache.c
+++ b/mm/tcache.c
@@ -903,13 +903,15 @@ tcache_invalidate_node_pages(struct tcache_node *node)
 	struct page *pages[TCACHE_PAGEVEC_SIZE];
 	pgoff_t index = 0;
 	unsigned nr_pages;
+	bool repeat;
 	int i;
 
 	/*
 	 * First forbid new page insertions - see tcache_page_tree_replace.
 	 */
 	node->invalidated = true;
-
+again:
+	repeat = false;
 	while ((nr_pages = tcache_lookup(pages, node, index,
 						TCACHE_PAGEVEC_SIZE, indices))) {
 		for (i = 0; i < nr_pages; i++) {
@@ -925,13 +927,20 @@ tcache_invalidate_node_pages(struct tcache_node *node)
 				tcache_lru_del(node->pool, page, false);
 				local_irq_enable();
 				tcache_put_page(page);
-			} else
+			} else {
 				local_irq_enable();
+				repeat = true;
+			}
 		}
 		cond_resched();
 		index++;
 	}
 
+	if (repeat) {
+		index = 0;
+		goto again;
+	}
+
 	WARN_ON(node->nr_pages != 0);
 }