From 59749e6ce53735d8b696763742225f126e94603f Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 12 Dec 2016 16:43:35 -0800
Subject: [PATCH] mm: khugepaged: fix radix tree node leak in shmem collapse
error path
The radix tree counts valid entries in each tree node. Entries stored
in the tree cannot be removed by simpling storing NULL in the slot or
the internal counters will be off and the node never gets freed again.
When collapsing a shmem page fails, restore the holes that were filled
with radix_tree_insert() with a proper radix tree deletion.
Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages")
Link: http://lkml.kernel.org/r/20161117191138.22769-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Jan Kara <jack@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
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/khugepaged.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 2779c63bdea0a..5d7c006373d30 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1525,9 +1525,11 @@ static void collapse_shmem(struct mm_struct *mm,
if (!page || iter.index < page->index) {
if (!nr_none)
break;
- /* Put holes back where they were */
- radix_tree_replace_slot(slot, NULL);
nr_none--;
+ /* Put holes back where they were */
+ radix_tree_delete(&mapping->page_tree,
+ iter.index);
+ slot = radix_tree_iter_next(&iter);
continue;
}
--
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