UBIFS: avoid unnecessary checks

I have a habit of compiling kernel with
EXTRA_CFLAGS="-Wextra -Wno-unused -Wno-sign-compare -Wno-missing-field-initializers"
and so fs/ubifs/key.h give lots (~10) of these every time:

CC      fs/ubifs/tnc_misc.o
In file included from fs/ubifs/ubifs.h:1725,
from fs/ubifs/tnc_misc.c:30:
fs/ubifs/key.h: In function 'key_r5_hash':
fs/ubifs/key.h:64: warning: comparison of unsigned expression >= 0 is always true
fs/ubifs/key.h: In function 'key_test_hash':
fs/ubifs/key.h:81: warning: comparison of unsigned expression >= 0 is always true

This patch fixes the warnings.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/key.h

@@ -37,6 +37,22 @@
 #ifndef __UBIFS_KEY_H__
 #define __UBIFS_KEY_H__
 
+/**
+ * key_mask_hash - mask a valid hash value.
+ * @val: value to be masked
+ *
+ * We use hash values as offset in directories, so values %0 and %1 are
+ * reserved for "." and "..". %2 is reserved for "end of readdir" marker. This
+ * function makes sure the reserved values are not used.
+ */
+static inline uint32_t key_mask_hash(uint32_t hash)
+{
+	hash &= UBIFS_S_KEY_HASH_MASK;
+	if (unlikely(hash <= 2))
+		hash += 3;
+	return hash;
+}
+
 /**
  * key_r5_hash - R5 hash function (borrowed from reiserfs).
  * @s: direntry name
@@ -54,16 +70,7 @@ static inline uint32_t key_r5_hash(const char *s, int len)
 		str++;
 	}
 
-	a &= UBIFS_S_KEY_HASH_MASK;
-
-	/*
-	 * We use hash values as offset in directories, so values %0 and %1 are
-	 * reserved for "." and "..". %2 is reserved for "end of readdir"
-	 * marker.
-	 */
-	if (unlikely(a >= 0 && a <= 2))
-		a += 3;
-	return a;
+	return key_mask_hash(a);
 }
 
 /**
@@ -77,10 +84,7 @@ static inline uint32_t key_test_hash(const char *str, int len)
 
 	len = min_t(uint32_t, len, 4);
 	memcpy(&a, str, len);
-	a &= UBIFS_S_KEY_HASH_MASK;
-	if (unlikely(a >= 0 && a <= 2))
-		a += 3;
-	return a;
+	return key_mask_hash(a);
 }
 
 /**