The patch titled
Subject: include/linux/bitmap.h: make bitmap_fill() and bitmap_zero() consistent
has been added to the -mm tree. Its filename is
bitmap-make-bitmap_fill-and-bitmap_zero-consistent.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/bitmap-make-bitmap_fill-and-bitmap_zero-consistent.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/bitmap-make-bitmap_fill-and-bitmap_zero-consistent.patch
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From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxx
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Suggested-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/bitmap.h | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff -puN include/linux/bitmap.h~bitmap-make-bitmap_fill-and-bitmap_zero-consistent include/linux/bitmap.h
--- a/include/linux/bitmap.h~bitmap-make-bitmap_fill-and-bitmap_zero-consistent
+++ a/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
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,
_
Patches currently in -mm which might be from andriy.shevchenko@xxxxxxxxxxxxxxx are
scripts-decodecode-make-it-take-multiline-code-line.patch
bitmap-add-bitmap_zero-bitmap_clear-test-cases.patch
bitmap-add-bitmap_fill-bitmap_set-test-cases.patch
bitmap-clean-up-test_zero_fill_copy-test-case-and-rename.patch
bitmap-make-bitmap_fill-and-bitmap_zero-consistent.patch
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