include/linux/bitops.h: set_mask_bits() to return old value

| > Also, set_mask_bits is used in fs quite a bit and we can possibly come up
| > with a generic llsc based implementation (w/o the cmpxchg loop)
|
| May I also suggest changing the return value of set_mask_bits() to old.
|
| You can compute the new value given old, but you cannot compute the old
| value given new, therefore old is the better return value. Also, no
| current user seems to use the return value, so changing it is without
| risk.

Link: http://lkml.kernel.org/g/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Vineet Gupta <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Reviewed-by: Anthony Yznaga <[email protected]>
Acked-by: Will Deacon <[email protected]>
Cc: Miklos Szeredi <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/bitops.h

@@ -246,7 +246,7 @@ static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
 		new__ = (old__ & ~mask__) | bits__;		\
 	} while (cmpxchg(ptr, old__, new__) != old__);		\
 								\
-	new__;							\
+	old__;							\
 })
 #endif