From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754602AbeDBW6l (ORCPT ); Mon, 2 Apr 2018 18:58:41 -0400 Received: from mail-pl0-f66.google.com ([209.85.160.66]:45419 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754522AbeDBW6k (ORCPT ); Mon, 2 Apr 2018 18:58:40 -0400 X-Google-Smtp-Source: AIpwx4/b6L016KxVZGlFb8sLtNBleTsvydaEJKNDoIQOzx/L5tWhY+429FydKx87e3XibIaKEXrYMQ== From: Omar Sandoval To: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Cc: kernel-team@fb.com, Matthew Wilcox , Andrew Morton , Rasmus Villemoes , Linus Torvalds , stable@kernel.org Subject: [PATCH] bitmap: fix memset optimization on big-endian systems Date: Mon, 2 Apr 2018 15:58:31 -0700 Message-Id: <817147544aa3ecc2b78d6cadeab713869d8805e6.1522709616.git.osandov@fb.com> X-Mailer: git-send-email 2.16.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Omar Sandoval Commit 2a98dc028f91 introduced an optimization to bitmap_{set,clear}() which uses memset() when the start and length are constants aligned to a byte. This is wrong on big-endian systems; our bitmaps are arrays of unsigned long, so bit n is not at byte n / 8 in memory. This was caught by the Btrfs selftests, but the bitmap selftests also fail when run on a big-endian machine. We can still use memset if the start and length are aligned to an unsigned long, so do that on big-endian. The same problem applies to the memcmp in bitmap_equal(), so fix it there, too. Fixes: 2a98dc028f91 ("include/linux/bitmap.h: turn bitmap_set and bitmap_clear into memset when possible") Fixes: 2c6deb01525a ("bitmap: use memcmp optimisation in more situations") Cc: stable@kernel.org Reported-by: "Erhard F." Signed-off-by: Omar Sandoval --- include/linux/bitmap.h | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-) diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 5f11fbdc27f8..1ee46f492267 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -302,12 +302,20 @@ static inline void bitmap_complement(unsigned long *dst, const unsigned long *sr __bitmap_complement(dst, src, nbits); } +#ifdef __LITTLE_ENDIAN +#define BITMAP_MEM_ALIGNMENT 8 +#else +#define BITMAP_MEM_ALIGNMENT (8 * sizeof(unsigned long)) +#endif +#define BITMAP_MEM_MASK (BITMAP_MEM_ALIGNMENT - 1) + static inline int bitmap_equal(const unsigned long *src1, const unsigned long *src2, unsigned int nbits) { if (small_const_nbits(nbits)) return !((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits)); - if (__builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8)) + if (__builtin_constant_p(nbits & BITMAP_MEM_MASK) && + IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT)) return !memcmp(src1, src2, nbits / 8); return __bitmap_equal(src1, src2, nbits); } @@ -358,8 +366,10 @@ static __always_inline void bitmap_set(unsigned long *map, unsigned int start, { if (__builtin_constant_p(nbits) && nbits == 1) __set_bit(start, map); - else if (__builtin_constant_p(start & 7) && IS_ALIGNED(start, 8) && - __builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8)) + else if (__builtin_constant_p(start & BITMAP_MEM_MASK) && + IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) && + __builtin_constant_p(nbits & BITMAP_MEM_MASK) && + IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT)) memset((char *)map + start / 8, 0xff, nbits / 8); else __bitmap_set(map, start, nbits); @@ -370,8 +380,10 @@ static __always_inline void bitmap_clear(unsigned long *map, unsigned int start, { if (__builtin_constant_p(nbits) && nbits == 1) __clear_bit(start, map); - else if (__builtin_constant_p(start & 7) && IS_ALIGNED(start, 8) && - __builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8)) + else if (__builtin_constant_p(start & BITMAP_MEM_MASK) && + IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) && + __builtin_constant_p(nbits & BITMAP_MEM_MASK) && + IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT)) memset((char *)map + start / 8, 0, nbits / 8); else __bitmap_clear(map, start, nbits); -- 2.16.3