On 10/11/19 4:25 PM, John Snow wrote:
From: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
hbitmap_reset has an unobvious property: it rounds requested region up.
It may provoke bugs, like in recently fixed write-blocking mode of
mirror: user calls reset on unaligned region, not keeping in mind that
there are possible unrelated dirty bytes, covered by rounded-up region
and information of this unrelated "dirtiness" will be lost.
Make hbitmap_reset strict: assert that arguments are aligned, allowing
only one exception when @start + @count == hb->orig_size. It's needed
to comfort users of hbitmap_next_dirty_area, which cares about
hb->orig_size.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
Reviewed-by: Max Reitz <mreitz@xxxxxxxxxx>
Message-Id: <20190806152611.280389-1-vsementsov@xxxxxxxxxxxxx>
[Maintainer edit: Max's suggestions from on-list. --js]
Signed-off-by: John Snow <jsnow@xxxxxxxxxx>
---
include/qemu/hbitmap.h | 5 +++++
tests/test-hbitmap.c | 2 +-
util/hbitmap.c | 4 ++++
3 files changed, 10 insertions(+), 1 deletion(-)
+++ b/util/hbitmap.c
@@ -476,6 +476,10 @@ void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count)
/* Compute range in the last layer. */
uint64_t first;
uint64_t last = start + count - 1;
+ uint64_t gran = 1ULL << hb->granularity;
+
+ assert(!(start & (gran - 1)));
+ assert(!(count & (gran - 1)) || (start + count == hb->orig_size));
I know I'm replying a bit late (since this is now a pull request), but
would it be worth using the dedicated macro:
assert(QEMU_IS_ALIGNED(start, gran));
assert(QEMU_IS_ALIGNED(count, gran) || start + count == hb->orig_size);
instead of open-coding it? (I would also drop the extra () around the
right half of ||). If we want it, that would now be a followup patch.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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