mm: workingset: turn shadow node shrinker bugs into warnings (b936887e) · Commits · 戴 / test

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

+12 −8

Original line number	Diff line number	Diff line
		@@ -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:

Admin message