6.1-stable review patch. If anyone has any objections, please let me know.
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From: Hugh Dickins hughd@google.com
commit e5548f85b4527c4c803b7eae7887c10bf8f90c97 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/shmem.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/shmem.c +++ b/mm/shmem.c @@ -800,14 +800,16 @@ unsigned long shmem_partial_swap_usage(s 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();