]> git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/commit
bitmap: fix memset optimization on big-endian systems
authorOmar Sandoval <osandov@fb.com>
Mon, 2 Apr 2018 22:58:31 +0000 (15:58 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 3 Apr 2018 03:52:27 +0000 (20:52 -0700)
commit21035965f60b0502fc6537b232839389bb4ce664
treeb4c969cd182d8e30dd9b0123c945f200ab50f14a
parentf5a8eb632b562bd9c16c389f5db3a5260fba4157
bitmap: fix memset optimization on big-endian systems

Commit 2a98dc028f91 ("include/linux/bitmap.h: turn bitmap_set and
bitmap_clear into memset when possible") 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." <erhard_f@mailbox.org>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
include/linux/bitmap.h