This is a note to let you know that I've just added the patch titled
shmem: fix smaps BUG sleeping while atomic
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
shmem-fix-smaps-bug-sleeping-while-atomic.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e5548f85b4527c4c803b7eae7887c10bf8f90c97 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@xxxxxxxxxx>
Date: Tue, 22 Aug 2023 22:14:47 -0700
Subject: shmem: fix smaps BUG sleeping while atomic
From: Hugh Dickins <hughd@xxxxxxxxxx>
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@xxxxxxxxxx
Fixes: 230100321518 ("mm/smaps: simplify shmem handling of pte holes")
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.16+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/mm/shmem.c
+++ b/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 stable-queue which might be from hughd@xxxxxxxxxx are
queue-6.4/shmem-fix-smaps-bug-sleeping-while-atomic.patch
