Commit 7b57976d authored Jun 12, 2013 by Akinobu Mita Committed by Linus Torvalds Jun 12, 2013

frontswap: fix incorrect zeroing and allocation size for frontswap_map



The bitmap accessed by bitops must have enough size to hold the required
numbers of bits rounded up to a multiple of BITS_PER_LONG.  And the
bitmap must not be zeroed by memset() if the number of bits cleared is
not a multiple of BITS_PER_LONG.

This fixes incorrect zeroing and allocation size for frontswap_map.  The
incorrect zeroing part doesn't cause any problem because frontswap_map
is freed just after zeroing.  But the wrongly calculated allocation size
may cause the problem.

For 32bit systems, the allocation size of frontswap_map is about twice
as large as required size.  For 64bit systems, the allocation size is
smaller than requeired if the number of bits is not a multiple of
BITS_PER_LONG.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 736f3203

mm/frontswap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -319,7 +319,7 @@ void __frontswap_invalidate_area(unsigned type)
		return;
		frontswap_ops->invalidate_area(type);
		atomic_set(&sis->frontswap_pages, 0);
		memset(sis->frontswap_map, 0, sis->max / sizeof(long));
		bitmap_zero(sis->frontswap_map, sis->max);
		}
		clear_bit(type, need_init);
		}

mm/swapfile.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2116,7 +2116,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
		}
		/* frontswap enabled? set up bit-per-page map for frontswap */
		if (frontswap_enabled)
		frontswap_map = vzalloc(maxpages / sizeof(long));
		frontswap_map = vzalloc(BITS_TO_LONGS(maxpages) * sizeof(long));

		if (p->bdev) {
		if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {

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