diff mbox series

[089/166] include/linux/swapops.h: correct guards for non_swap_entry()

Message ID 20200407030843.XB8zAqurU%akpm@linux-foundation.org (mailing list archive)
State New, archived
Headers show
Series [001/166] mm, memcg: bypass high reclaim iteration for cgroup hierarchy root | expand

Commit Message

Andrew Morton April 7, 2020, 3:08 a.m. UTC 
From: Steven Price <steven.price@arm.com>
Subject: include/linux/swapops.h: correct guards for non_swap_entry()

If CONFIG_DEVICE_PRIVATE is defined, but neither CONFIG_MEMORY_FAILURE nor
CONFIG_MIGRATION, then non_swap_entry() will return 0, meaning that the
condition (non_swap_entry(entry) && is_device_private_entry(entry)) in
zap_pte_range() will never be true even if the entry is a device private
one.

Equally any other code depending on non_swap_entry() will not function as
expected.

I originally spotted this just by looking at the code, I haven't actually
observed any problems.

Looking a bit more closely it appears that actually this situation
(currently at least) cannot occur:

DEVICE_PRIVATE depends on ZONE_DEVICE
ZONE_DEVICE depends on MEMORY_HOTREMOVE
MEMORY_HOTREMOVE depends on MIGRATION

Link: http://lkml.kernel.org/r/20200305130550.22693-1-steven.price@arm.com
Fixes: 5042db43cc26 ("mm/ZONE_DEVICE: new type of ZONE_DEVICE for unaddressable memory")
Signed-off-by: Steven Price <steven.price@arm.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/swapops.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

--- a/include/linux/swapops.h~mm-correct-guards-for-non_swap_entry
+++ a/include/linux/swapops.h
@@ -350,7 +350,8 @@  static inline void num_poisoned_pages_in
 }
 #endif
 
-#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION)
+#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION) || \
+    defined(CONFIG_DEVICE_PRIVATE)
 static inline int non_swap_entry(swp_entry_t entry)
 {
 	return swp_type(entry) >= MAX_SWAPFILES;