From: Joe Korty <joe.korty@ccur.com>
This patch replaces the call to bitmap_shift_right() in bitmap_parse() with
bitmap_shift_left().
I also prepended comments to the bitmap_shift_* functions defining what
'left' and 'right' means. This is under the theory that if I and all the
reviewers were bamboozled, others in the future occasionally might be too.
---
25-akpm/lib/bitmap.c | 24 +++++++++++++++++++++++-
1 files changed, 23 insertions(+), 1 deletion(-)
diff -puN lib/bitmap.c~bitmap_parse-fix lib/bitmap.c
--- 25/lib/bitmap.c~bitmap_parse-fix 2004-03-22 20:17:39.592327032 -0800
+++ 25-akpm/lib/bitmap.c 2004-03-22 20:17:39.596326424 -0800
@@ -71,6 +71,17 @@ void bitmap_complement(unsigned long *bi
}
EXPORT_SYMBOL(bitmap_complement);
+/*
+ * bitmap_shift_write - logical right shift of the bits in a bitmap
+ * @dst - destination bitmap
+ * @src - source bitmap
+ * @nbits - shift by this many bits
+ * @bits - bitmap size, in bits
+ *
+ * Shifting right (dividing) means moving bits in the MS -> LS bit
+ * direction. Zeros are fed into the vacated MS positions and the
+ * LS bits shifted off the bottom are lost.
+ */
void bitmap_shift_right(unsigned long *dst,
const unsigned long *src, int shift, int bits)
{
@@ -86,6 +97,17 @@ void bitmap_shift_right(unsigned long *d
}
EXPORT_SYMBOL(bitmap_shift_right);
+/*
+ * bitmap_shift_left - logical left shift of the bits in a bitmap
+ * @dst - destination bitmap
+ * @src - source bitmap
+ * @nbits - shift by this many bits
+ * @bits - bitmap size, in bits
+ *
+ * Shifting left (multiplying) means moving bits in the LS -> MS
+ * direction. Zeros are fed into the vacated LS bit positions
+ * and those MS bits shifted off the top are lost.
+ */
void bitmap_shift_left(unsigned long *dst,
const unsigned long *src, int shift, int bits)
{
@@ -269,7 +291,7 @@ int bitmap_parse(const char __user *ubuf
if (nchunks == 0 && chunk == 0)
continue;
- bitmap_shift_right(maskp, maskp, CHUNKSZ, nmaskbits);
+ bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits);
*maskp |= chunk;
nchunks++;
nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
_