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 it again.
In this case the page remains not invalidated, and tcache_node->nr_pages
never decremented. Later, we catch WARN_ON() reporting about this.
tcache_shrink_scan() tcache_destroy_pool
tcache_lru_isolate()
tcache_grab_pool()
...
page_cache_get_speculative() -->cnt == 2
...
tcache_put_pool() --> pool cnt zero
...
wait_for_completion(&pool->completion);
tcache_reclaim_pages
tcache_invalidate_node_pages()
__tcache_reclaim_page() tcache_lookup()
page_cache_get_speculative --> cnt == 3
__tcache_page_tree_delete
page_ref_freeze(2) -->fail
page_ref_freeze(2) -->fail
The patch fixes the problem. In case of we failed to invalidate a page,
we remember this, and return to such pages after others are invalidated.
https://jira.sw.ru/browse/PSBM-78354
v2: Also fix tcache_detach_page()
Signed-off-by: Kirill Tkhai
---
mm/tcache.c | 21 +++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/mm/tcache.c b/mm/tcache.c
index d1a2c53e11a3..760e417d491b 100644
--- a/mm/tcache.c
+++ b/mm/tcache.c
@@ -850,6 +850,14 @@ static struct page *tcache_detach_page(struct tcache_node
*node, pgoff_t index,
if (page)
tcache_lru_del(node->pool, page, reused);
local_irq_restore(flags);
+ /*
+* Shrinker could isolated the page in parallel
+* with us. This case page_ref_freeze(page, 2)
+* in __tcache_page_tree_delete() fails, and
+* we have to repeat the cycle.
+*/
+ if (!page)
+ goto repeat;
}
return page;
@@ -903,13 +911,15 @@ 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 +935,20 @@ 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);
}
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