| Message ID | 6fe3b3ec-abdf-332f-5c23-6a3b3a3b11a9@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [mm-hotfixes-unstable] shmem: fix smaps BUG sleeping while atomic | expand |
On Tue, Aug 22, 2023 at 10:14:47PM -0700, Hugh Dickins wrote: > 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@google.com> > Cc: stable@vger.kernel.org # 5.16+ Oops.. thanks Hugh. Acked-by: Peter Xu <peterx@redhat.com>
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();
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@google.com> Cc: stable@vger.kernel.org # 5.16+ --- mm/shmem.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)