compiler.h: cast away attributes in WRITE_ONCE magic

kernel build bot showed a warning triggered by commit
76695af20c01 ("locking, arch: use WRITE_ONCE()/READ_ONCE() in
smp_store_release()/smp_load_acquire()"). Turns out that sparse
does not like WRITE_ONCE accessing elements from the (sparse)
rcu address space.

fs/afs/inode.c:448:9: sparse: incorrect type in initializer (different address spaces)
fs/afs/inode.c:448:9:    expected struct afs_permits *__val
fs/afs/inode.c:448:9:    got void [noderef] <asn:4>*<noident>

Solution is to force cast away the sparse attributes for the initializer
of the union in WRITE_SAME. As this now gets too long, lets split
the macro.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index e08a6ae7c0a422fa72fe0b05d47faf14e651e5fb..c836eb2dc44d5b3a4d5e98dfbbd274c4448daa90 100644 (file)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -252,7 +252,12 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
        ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
 
 #define WRITE_ONCE(x, val) \
-       ({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
+({                                                     \
+       union { typeof(x) __val; char __c[1]; } __u =   \
+               { .__val = (__force typeof(x)) (val) }; \
+       __write_once_size(&(x), __u.__c, sizeof(x));    \
+       __u.__val;                                      \
+})
 
 /**
  * READ_ONCE_CTRL - Read a value heading a control dependency