cpumask: add cpumask_scnprintf_len function

Add a new function cpumask_scnprintf_len() to return the number of
characters needed to display "len" cpumask bits.  The current method
of allocating NR_CPUS bytes is incorrect as what's really needed is
9 characters per 32-bit word of cpumask bits (8 hex digits plus the
seperator [','] or the terminating NULL.)  This function provides the
caller the means to allocate the correct string length.

Cc: Paul Jackson <pj@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 16 insertions, 0 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 2c9242e..a6939e1 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -316,6 +316,22 @@ int bitmap_scnprintf(char *buf, unsigned int buflen,
 EXPORT_SYMBOL(bitmap_scnprintf);
 
 /**
+ * bitmap_scnprintf_len - return buffer length needed to convert
+ * bitmap to an ASCII hex string.
+ * @len: number of bits to be converted
+ */
+int bitmap_scnprintf_len(unsigned int len)
+{
+	/* we need 9 chars per word for 32 bit words (8 hexdigits + sep/null) */
+	int bitslen = ALIGN(len, CHUNKSZ);
+	int wordlen = CHUNKSZ / 4;
+	int buflen = (bitslen / wordlen) * (wordlen + 1) * sizeof(char);
+
+	return buflen;
+}
+EXPORT_SYMBOL(bitmap_scnprintf_len);
+
+/**
  * __bitmap_parse - convert an ASCII hex string into a bitmap.
  * @buf: pointer to buffer containing string.
  * @buflen: buffer size in bytes.  If string is smaller than this