[PATCH] atomic: inc_not_zero

Introduce an atomic_inc_not_zero operation.  Make this a special case of
atomic_add_unless because lockless pagecache actually wants
atomic_inc_not_negativeone due to its offset refcount.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/asm-frv/atomic.h b/include/asm-frv/atomic.h
index 55f06a0e949f..f6539ff569c5 100644
--- a/include/asm-frv/atomic.h
+++ b/include/asm-frv/atomic.h
@@ -416,4 +416,14 @@ extern uint32_t __cmpxchg_32(uint32_t *v, uint32_t test, uint32_t new);
 
 #define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
 
+#define atomic_add_unless(v, a, u)                              \
+({                                                              \
+        int c, old;                                             \
+        c = atomic_read(v);                                     \
+        while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
+                c = old;                                        \
+        c != (u);                                               \
+})
+#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
+
 #endif /* _ASM_ATOMIC_H */