[PATCH] mm: add dummy can_do_mlock() helper

[Arnd Bergmann]

On kernels without CONFIG_MMU, we get a link error for the siw
driver:

drivers/infiniband/sw/siw/siw_mem.o: In function `siw_umem_get':
siw_mem.c:(.text+0x4c8): undefined reference to `can_do_mlock'

This is probably not the only driver that needs the function
and could otherwise build correctly without CONFIG_MMU, so
add a dummy variant that always returns false.

Fixes: 2251334dcac9 ("rdma/siw: application buffer management")
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
 include/linux/mm.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 66f296181bcc..cc292273e6ba 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1424,7 +1424,11 @@ extern void pagefault_out_of_memory(void);
 
 extern void show_free_areas(unsigned int flags, nodemask_t *nodemask);
 
+#ifdef CONFIG_MMU
 extern bool can_do_mlock(void);
+#else
+static inline bool can_do_mlock(void) { return false; }
+#endif
 extern int user_shm_lock(size_t, struct user_struct *);
 extern void user_shm_unlock(size_t, struct user_struct *);
 
-- 
2.20.0