smaps_pte_hole_lookup() is calling shmem_partial_swap_usage() with page
table lock held: but shmem_partial_swap_usage() does cond_resched_rcu()
if need_resched(): "BUG: sleeping function called from invalid context".
Since shmem_partial_swap_usage() is designed to count across a range, but
smaps_pte_hole_lookup() only calls it for a single page slot, just break
out of the loop on the last or only page, before checking need_resched().
Fixes: 230100321518 ("mm/smaps: simplify shmem handling of pte holes")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 5.16+
---
mm/shmem.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 7a0c1e19d9f8..c512a5e82f8d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -806,14 +806,16 @@ unsigned long shmem_partial_swap_usage(struct address_space *mapping,
XA_STATE(xas, &mapping->i_pages, start);
struct page *page;
unsigned long swapped = 0;
+ unsigned long max = end - 1;
rcu_read_lock();
- xas_for_each(&xas, page, end - 1) {
+ xas_for_each(&xas, page, max) {
if (xas_retry(&xas, page))
continue;
if (xa_is_value(page))
swapped++;
-
+ if (xas.xa_index == max)
+ break;
if (need_resched()) {
xas_pause(&xas);
cond_resched_rcu();
--
2.35.3
