include/linux/bitmap.h: make bitmap_fill() and bitmap_zero() consistent
Behaviour of bitmap_fill() differs from bitmap_zero() in a way how bits
behind bitmap are handed. bitmap_zero() clears entire bitmap by unsigned
long boundary, while bitmap_fill() mimics bitmap_set().
Here we change bitmap_fill() behaviour to be consistent with bitmap_zero()
and add a note to documentation.
The change might reveal some bugs in the code where unused bits are
handled differently and in such cases bitmap_set() has to be used.
Link: http://lkml.kernel.org/r/20180109172430.87452-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Yury Norov <ynorov@caviumnetworks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index e43533e..d9bf699 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -67,6 +67,11 @@
* bitmap_from_arr32(dst, buf, nbits) Copy nbits from u32[] buf to dst
* bitmap_to_arr32(buf, src, nbits) Copy nbits from buf to u32[] dst
*
+ * Note, bitmap_zero() and bitmap_fill() operate over the region of
+ * unsigned longs, that is, bits behind bitmap till the unsigned long
+ * boundary will be zeroed or filled as well. Consider to use
+ * bitmap_clear() or bitmap_set() to make explicit zeroing or filling
+ * respectively.
*/
/**
@@ -202,12 +207,12 @@ static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
static inline void bitmap_fill(unsigned long *dst, unsigned int nbits)
{
- unsigned int nlongs = BITS_TO_LONGS(nbits);
- if (!small_const_nbits(nbits)) {
- unsigned int len = (nlongs - 1) * sizeof(unsigned long);
- memset(dst, 0xff, len);
+ if (small_const_nbits(nbits))
+ *dst = ~0UL;
+ else {
+ unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
+ memset(dst, 0xff, len);
}
- dst[nlongs - 1] = BITMAP_LAST_WORD_MASK(nbits);
}
static inline void bitmap_copy(unsigned long *dst, const unsigned long *src,