[RFC] PTR_ERR: return 0 if ptr isn't an error value.

[Rusty Russell]

Back in 2011, Uwe Kleine-KÃnig added the nonsensically-named
PTR_RET(), providing a means to avoid if() statements in code (commit 
fa9ee9c4b9).

Instead, just make PTR_ERR() return 0 if the pointer isn't an error
value.  This is harmless, since PTR_ERR() should have never been
passed a non-error value.  And GCC is usually smart enough to remove
the extra test if IS_ERR() has already been called.

My vmlinux text increased by 300 bytes:

	   text	   data	    bss	    dec	    hex	filename
	6029452	 491628	2576384	9097464	 8ad0f8	vmlinux
	6029721	 491628	2576384	9097733	 8ad205	vmlinux.PTR_ERR

Cc: Uwe Kleine-KÃnig <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Thomas Meyer <thomas@xxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>

diff --git a/include/linux/err.h b/include/linux/err.h
index f2edce2..621d859 100644
--- a/include/linux/err.h
+++ b/include/linux/err.h
@@ -24,14 +24,16 @@ static inline void * __must_check ERR_PTR(long error)
 	return (void *) error;
 }
 
-static inline long __must_check PTR_ERR(const void *ptr)
+static inline long __must_check IS_ERR(const void *ptr)
 {
-	return (long) ptr;
+	return IS_ERR_VALUE((unsigned long)ptr);
 }
 
-static inline long __must_check IS_ERR(const void *ptr)
+static inline long __must_check PTR_ERR(const void *ptr)
 {
-	return IS_ERR_VALUE((unsigned long)ptr);
+	if (IS_ERR(ptr))
+		return (long) ptr;
+	return 0;
 }
 
 static inline long __must_check IS_ERR_OR_NULL(const void *ptr)
@@ -52,14 +54,7 @@ static inline void * __must_check ERR_CAST(const void *ptr)
 	return (void *) ptr;
 }
 
-static inline int __must_check PTR_RET(const void *ptr)
-{
-	if (IS_ERR(ptr))
-		return PTR_ERR(ptr);
-	else
-		return 0;
-}
-
+#define PTR_RET	PTR_ERR
 #endif
 
 #endif /* _LINUX_ERR_H */
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