[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, 15 insertions, 0 deletions

diff --git a/include/asm-sh/atomic.h b/include/asm-sh/atomic.h
index a148c762d366..aabfd334462c 100644
--- a/include/asm-sh/atomic.h
+++ b/include/asm-sh/atomic.h
@@ -101,6 +101,21 @@ static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
         return ret;
 }
 
+static inline int atomic_add_unless(atomic_t *v, int a, int u)
+{
+        int ret;
+        unsigned long flags;
+
+        local_irq_save(flags);
+        ret = v->counter;
+        if (ret != u)
+                v->counter += a;
+        local_irq_restore(flags);
+
+        return ret != u;
+}
+#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
+
 static __inline__ void atomic_clear_mask(unsigned int mask, atomic_t *v)
 {
         unsigned long flags;