bitops: Add __ffs64 bitop
Finds the first set bit in a 64 bit word. This is required in order
to fix a bug in GFS2, but I think it should be a generic function
in case of future users.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Willy Tarreau <w@1wt.eu>
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 6182913..c05a29c 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -112,6 +112,25 @@
return fls64(l);
}
+/**
+ * __ffs64 - find first set bit in a 64 bit word
+ * @word: The 64 bit word
+ *
+ * On 64 bit arches this is a synomyn for __ffs
+ * The result is not defined if no bits are set, so check that @word
+ * is non-zero before calling this.
+ */
+static inline unsigned long __ffs64(u64 word)
+{
+#if BITS_PER_LONG == 32
+ if (((u32)word) == 0UL)
+ return __ffs((u32)(word >> 32)) + 32;
+#elif BITS_PER_LONG != 64
+#error BITS_PER_LONG not 32 or 64
+#endif
+ return __ffs((unsigned long)word);
+}
+
#ifdef __KERNEL__
#ifdef CONFIG_GENERIC_FIND_FIRST_BIT