[merged mm-hotfixes-stable] shmem-fix-smaps-bug-sleeping-while-atomic.patch removed from -mm tree

[merged mm-hotfixes-stable] shmem-fix-smaps-bug-sleeping-while-atomic.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: shmem: fix smaps BUG sleeping while atomic
has been removed from the -mm tree.  Its filename was
     shmem-fix-smaps-bug-sleeping-while-atomic.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Hugh Dickins <hughd@google.com>
Subject: shmem: fix smaps BUG sleeping while atomic
Date: Tue, 22 Aug 2023 22:14:47 -0700 (PDT)

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>
---

 mm/shmem.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/shmem.c~shmem-fix-smaps-bug-sleeping-while-atomic
+++ a/mm/shmem.c
@@ -806,14 +806,16 @@ 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();
_

Patches currently in -mm which might be from hughd@google.com are

mm-khugepaged-fix-collapse_pte_mapped_thp-versus-uffd.patch