From 7e934cf5ace1dceeb804f7493fa28bb697ed3c52 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Thu, 12 Mar 2020 17:29:11 -0400 Subject: xarray: Fix early termination of xas_for_each_marked xas_for_each_marked() is using entry == NULL as a termination condition of the iteration. When xas_for_each_marked() is used protected only by RCU, this can however race with xas_store(xas, NULL) in the following way: TASK1 TASK2 page_cache_delete() find_get_pages_range_tag() xas_for_each_marked() xas_find_marked() off = xas_find_chunk() xas_store(&xas, NULL) xas_init_marks(&xas); ... rcu_assign_pointer(*slot, NULL); entry = xa_entry(off); And thus xas_for_each_marked() terminates prematurely possibly leading to missed entries in the iteration (translating to missing writeback of some pages or a similar problem). If we find a NULL entry that has been marked, skip it (unless we're trying to allocate an entry). Reported-by: Jan Kara CC: stable@vger.kernel.org Fixes: ef8e5717db01 ("page cache: Convert delete_batch to XArray") Signed-off-by: Matthew Wilcox (Oracle) --- tools/testing/radix-tree/main.c | 1 + 1 file changed, 1 insertion(+) (limited to 'tools/testing/radix-tree/main.c') diff --git a/tools/testing/radix-tree/main.c b/tools/testing/radix-tree/main.c index 7a22d6e3732e..f2cbc8e5b97c 100644 --- a/tools/testing/radix-tree/main.c +++ b/tools/testing/radix-tree/main.c @@ -311,6 +311,7 @@ int main(int argc, char **argv) regression4_test(); iteration_test(0, 10 + 90 * long_run); iteration_test(7, 10 + 90 * long_run); + iteration_test2(10 + 90 * long_run); single_thread_tests(long_run); /* Free any remaining preallocated nodes */ -- cgit v1.2.3