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authorHugh Dickins <hughd@google.com>2023-08-22 22:14:47 -0700
committerAndrew Morton <akpm@linux-foundation.org>2023-08-24 14:59:47 -0700
commite5548f85b4527c4c803b7eae7887c10bf8f90c97 (patch)
treee89cd6f78cdd98fedad9054d38f517249240016c
parentf84f62e69963d7742acec4340ec1c4c7ef22b887 (diff)
shmem: fix smaps BUG sleeping while atomic
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(). Link: https://lkml.kernel.org/r/6fe3b3ec-abdf-332f-5c23-6a3b3a3b11a9@google.com Fixes: 230100321518 ("mm/smaps: simplify shmem handling of pte holes") Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Peter Xu <peterx@redhat.com> Cc: <stable@vger.kernel.org> [5.16+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--mm/shmem.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index f5af4b943e42..d963c747dabc 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();