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| author | Yury Norov <yury.norov@gmail.com> | 2023-02-27 22:24:36 +0300 |
|---|---|---|
| committer | Yury Norov <yury.norov@gmail.com> | 2023-06-22 23:57:41 +0300 |
| commit | c1d2ba10f594046831d14b03f194e8d05e78abad (patch) | |
| tree | 6d6ad141cd6405d9620287e868a6b4770578fca8 | |
| parent | c4c14c290682e080da5cee81f4998062e1be274a (diff) | |
| download | linux-c1d2ba10f594046831d14b03f194e8d05e78abad.tar.xz | |
lib/bitmap: drop optimization of bitmap_{from,to}_arr64
bitmap_{from,to}_arr64() optimization is overly optimistic on 32-bit LE
architectures when it's wired to bitmap_copy_clear_tail().
bitmap_copy_clear_tail() takes care of unused bits in the bitmap up to
the next word boundary. But on 32-bit machines when copying bits from
bitmap to array of 64-bit words, it's expected that the unused part of
a recipient array must be cleared up to 64-bit boundary, so the last 4
bytes may stay untouched when nbits % 64 <= 32.
While the copying part of the optimization works correct, that clear-tail
trick makes corresponding tests reasonably fail:
test_bitmap: bitmap_to_arr64(nbits == 1): tail is not safely cleared: 0xa5a5a5a500000001 (must be 0x0000000000000001)
Fix it by removing bitmap_{from,to}_arr64() optimization for 32-bit LE
arches.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/lkml/20230225184702.GA3587246@roeck-us.net/
Fixes: 0a97953fd221 ("lib: add bitmap_{from,to}_arr64")
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
| -rw-r--r-- | include/linux/bitmap.h | 8 | ||||
| -rw-r--r-- | lib/bitmap.c | 2 |
2 files changed, 4 insertions, 6 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 7d6d73b78147..03644237e1ef 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -302,12 +302,10 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, #endif /* - * On 64-bit systems bitmaps are represented as u64 arrays internally. On LE32 - * machines the order of hi and lo parts of numbers match the bitmap structure. - * In both cases conversion is not needed when copying data from/to arrays of - * u64. + * On 64-bit systems bitmaps are represented as u64 arrays internally. So, + * the conversion is not needed when copying data from/to arrays of u64. */ -#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN) +#if BITS_PER_LONG == 32 void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits); void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits); #else diff --git a/lib/bitmap.c b/lib/bitmap.c index 1c81413c51f8..ddb31015e38a 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -1495,7 +1495,7 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits) EXPORT_SYMBOL(bitmap_to_arr32); #endif -#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN) +#if BITS_PER_LONG == 32 /** * bitmap_from_arr64 - copy the contents of u64 array of bits to bitmap * @bitmap: array of unsigned longs, the destination bitmap |