From cf1ba6a102b6ef962d58eb1fe3ef67994a1a8ab2 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 22 Aug 2023 22:14:47 -0700 Subject: [PATCH] UPSTREAM: 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(). Bug: 302977171 Link: https://lkml.kernel.org/r/6fe3b3ec-abdf-332f-5c23-6a3b3a3b11a9@google.com (cherry picked from commit e5548f85b4527c4c803b7eae7887c10bf8f90c97) Fixes: 230100321518 ("mm/smaps: simplify shmem handling of pte holes") Change-Id: I1b59341c954cb7eb31709ba0dcc65ec6e67c58c6 Signed-off-by: Hugh Dickins Acked-by: Peter Xu Cc: [5.16+] Signed-off-by: Andrew Morton --- mm/shmem.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index f5232a35f04d..90ffdfd35bc6 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -805,14 +805,16 @@ 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();