(2010/04/13 2:39), Marcelo Tosatti wrote:
On Mon, Apr 12, 2010 at 07:35:35PM +0900, Takuya Yoshikawa wrote:
This patch fixes a bug found by Avi during the review process
of my dirty bitmap related work.
To ppc and ia64 people:
The fix is really simple but touches all architectures using
dirty bitmaps. So please check this will not suffer your part.
===
Int is not long enough to store the size of a dirty bitmap.
This patch fixes this problem with the introduction of a wrapper
function to calculate the sizes of dirty bitmaps.
Note: in mark_page_dirty(), we have to consider the fact that
__set_bit() takes the offset as int, not long.
Signed-off-by: Takuya Yoshikawa<yoshikawa.takuya@xxxxxxxxxxxxx>
Applied, thanks.
Thanks everyone!
BTW, just from my curiosity, are there any cases in which we use such huge
number of pages currently?
ALIGN(memslot->npages, BITS_PER_LONG) / 8;
More than G pages need really big memory!
-- We are assuming some special cases like "short" int size?
If so, we may have to care about a lot of things from now on, because common
functions like __set_bit() don't support such long buffers.
If not, my patch might be over hacking -- especially the following part:
@@ -1183,10 +1183,13 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
memslot = gfn_to_memslot_unaliased(kvm, gfn);
if (memslot && memslot->dirty_bitmap) {
unsigned long rel_gfn = gfn - memslot->base_gfn;
+ unsigned long *p = memslot->dirty_bitmap +
+ rel_gfn / BITS_PER_LONG;
+ int offset = rel_gfn % BITS_PER_LONG;
/* avoid RMW */
- if (!generic_test_le_bit(rel_gfn, memslot->dirty_bitmap))
- generic___set_le_bit(rel_gfn, memslot->dirty_bitmap);
+ if (!generic_test_le_bit(offset, p))
+ generic___set_le_bit(offset, p);
}
}
--
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