From: Steven Price steven.price@arm.com
[ Upstream commit 3f3673d7d324d872d9d8ddb73b3e5e47fbf12e0d ]
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
Fixes: 5042db43cc26 ("mm/ZONE_DEVICE: new type of ZONE_DEVICE for unaddressable memory") Signed-off-by: Steven Price steven.price@arm.com Signed-off-by: Andrew Morton akpm@linux-foundation.org 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 Link: http://lkml.kernel.org/r/20200305130550.22693-1-steven.price@arm.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/swapops.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/include/linux/swapops.h b/include/linux/swapops.h index 877fd239b6fff..3208a520d0be3 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -348,7 +348,8 @@ static inline void num_poisoned_pages_inc(void) } #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;