The patch titled
Subject: mm-remove-an-avoidable-load-of-page-refcount-in-page_ref_add_unless-fix
has been added to the -mm mm-unstable branch. Its filename is
mm-remove-an-avoidable-load-of-page-refcount-in-page_ref_add_unless-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-remove-an-avoidable-load-of-page-refcount-in-page_ref_add_unless-fix.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm-remove-an-avoidable-load-of-page-refcount-in-page_ref_add_unless-fix
Date: Mon Dec 9 07:53:02 PM PST 2024
add comment from David
Link: https://lkml.kernel.org/r/f5a65bf5-5105-4376-9c1c-164a15a4ab79@xxxxxxxxxx
Cc: Mateusz Guzik <mjguzik@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/page_ref.h | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
--- a/include/linux/page_ref.h~mm-remove-an-avoidable-load-of-page-refcount-in-page_ref_add_unless-fix
+++ a/include/linux/page_ref.h
@@ -234,8 +234,15 @@ static inline bool page_ref_add_unless(s
rcu_read_lock();
/* avoid writing to the vmemmap area being remapped */
- if (!page_is_fake_head(page))
+ if (!page_is_fake_head(page)) {
+ /*
+ * atomic_add_unless() will currently never modify the value
+ * if it already is u. If that ever changes, we'd have to have
+ * a separate check here, such that we won't be writing to
+ * write-protected vmemmap areas.
+ */
ret = atomic_add_unless(&page->_refcount, nr, u);
+ }
rcu_read_unlock();
if (page_ref_tracepoint_active(page_ref_mod_unless))
_
Patches currently in -mm which might be from akpm@xxxxxxxxxxxxxxxxxxxx are
mm-vmscan-account-for-free-pages-to-prevent-infinite-loop-in-throttle_direct_reclaim-checkpatch-fixes.patch
mm-swap_cgroup-allocate-swap_cgroup-map-using-vcalloc-fix.patch
mm-page_alloc-add-some-detailed-comments-in-can_steal_fallback-fix.patch
mm-introduce-mmap_lock_speculate_try_beginretry-fix.patch
mm-damon-tests-vaddr-kunith-reduce-stack-consumption.patch
mm-remove-an-avoidable-load-of-page-refcount-in-page_ref_add_unless-fix.patch
xarray-port-tests-to-kunit-fix.patch
fault-inject-use-prandom-where-cryptographically-secure-randomness-is-not-needed-fix.patch
