The patch titled
Subject: shmem: fix smaps BUG sleeping while atomic
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
shmem-fix-smaps-bug-sleeping-while-atomic.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/shmem-fix-smaps-bug-sleeping-while-atomic.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
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@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>
---
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@xxxxxxxxxx are
shmem-fix-smaps-bug-sleeping-while-atomic.patch
