From b936887e8739d3fa83f87d899f68d136735d9816 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 12 Dec 2016 16:43:38 -0800
Subject: [PATCH] mm: workingset: turn shadow node shrinker bugs into warnings
When the shadow page shrinker tries to reclaim a radix tree node but
finds it in an unexpected state - it should contain no pages, and
non-zero shadow entries - there is no need to kill the executing task or
even the entire system. Warn about the invalid state, then leave that
tree node be. Simply don't put it back on the shadow LRU for future
reclaim and move on.
Link: http://lkml.kernel.org/r/20161117191138.22769-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/workingset.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/mm/workingset.c b/mm/workingset.c
index fb1f9183d89a3..98f830897b1ba 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -418,23 +418,27 @@ static enum lru_status shadow_lru_isolate(struct list_head *item,
* no pages, so we expect to be able to remove them all and
* delete and free the empty node afterwards.
*/
- BUG_ON(!workingset_node_shadows(node));
- BUG_ON(workingset_node_pages(node));
-
+ if (WARN_ON_ONCE(!workingset_node_shadows(node)))
+ goto out_invalid;
+ if (WARN_ON_ONCE(workingset_node_pages(node)))
+ goto out_invalid;
for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
if (node->slots[i]) {
- BUG_ON(!radix_tree_exceptional_entry(node->slots[i]));
+ if (WARN_ON_ONCE(!radix_tree_exceptional_entry(node->slots[i])))
+ goto out_invalid;
+ if (WARN_ON_ONCE(!mapping->nrexceptional))
+ goto out_invalid;
node->slots[i] = NULL;
workingset_node_shadows_dec(node);
- BUG_ON(!mapping->nrexceptional);
mapping->nrexceptional--;
}
}
- BUG_ON(workingset_node_shadows(node));
+ if (WARN_ON_ONCE(workingset_node_shadows(node)))
+ goto out_invalid;
inc_node_state(page_pgdat(virt_to_page(node)), WORKINGSET_NODERECLAIM);
- if (!__radix_tree_delete_node(&mapping->page_tree, node))
- BUG();
+ __radix_tree_delete_node(&mapping->page_tree, node);
+out_invalid:
spin_unlock(&mapping->tree_lock);
ret = LRU_REMOVED_RETRY;
out:
--
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