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authorSteven Whitehouse <swhiteho@redhat.com>2009-04-23 08:48:15 +0100
committerSteven Whitehouse <swhiteho@redhat.com>2009-04-23 10:06:35 +0100
commit952043ac12a117d8e94bddd9088338d7ad20ca7d (patch)
tree3ad716873d90392fbf1888084af9be7e5e242e1f /include/linux
parent091069740304c979f957ceacec39c461d0192158 (diff)
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>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/bitops.h19
1 files changed, 19 insertions, 0 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 61829139795..c05a29cb9bb 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -112,6 +112,25 @@ static inline unsigned fls_long(unsigned long l)
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