From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
To: qemu-block@nongnu.org
Cc: fam@euphon.net, kwolf@redhat.com, vsementsov@virtuozzo.com,
qemu-devel@nongnu.org, mreitz@redhat.com, den@openvz.org,
jsnow@redhat.com
Subject: [Qemu-devel] [PATCH v2] util/hbitmap: strict hbitmap_reset
Date: Tue, 6 Aug 2019 18:26:11 +0300 [thread overview]
Message-ID: <20190806152611.280389-1-vsementsov@virtuozzo.com> (raw)
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@virtuozzo.com>
---
v2 based on Max's https://github.com/XanClic/qemu.git block
which will be merged soon to 4.1, and this patch goes to 4.2
Based-on: https://github.com/XanClic/qemu.git block
v1 was "[PATCH] util/hbitmap: fix unaligned reset", and as I understand
we all agreed to just assert alignment instead of aligning down
automatically.
include/qemu/hbitmap.h | 5 +++++
tests/test-hbitmap.c | 2 +-
util/hbitmap.c | 4 ++++
3 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h
index 4afbe6292e..7865e819ca 100644
--- a/include/qemu/hbitmap.h
+++ b/include/qemu/hbitmap.h
@@ -132,6 +132,11 @@ void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t count);
* @count: Number of bits to reset.
*
* Reset a consecutive range of bits in an HBitmap.
+ * @start and @count must be aligned to bitmap granularity. The only exception
+ * is resetting the tail of the bitmap: @count may be equal to @start +
+ * hb->orig_size, in this case @count may be not aligned. @start + @count
+ * allowed to be greater than hb->orig_size, but only if @start < hb->orig_size
+ * and @start + @count = ALIGN_UP(hb->orig_size, granularity).
*/
void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count);
diff --git a/tests/test-hbitmap.c b/tests/test-hbitmap.c
index 592d8219db..2be56d1597 100644
--- a/tests/test-hbitmap.c
+++ b/tests/test-hbitmap.c
@@ -423,7 +423,7 @@ static void test_hbitmap_granularity(TestHBitmapData *data,
hbitmap_test_check(data, 0);
hbitmap_test_set(data, 0, 3);
g_assert_cmpint(hbitmap_count(data->hb), ==, 4);
- hbitmap_test_reset(data, 0, 1);
+ hbitmap_test_reset(data, 0, 2);
g_assert_cmpint(hbitmap_count(data->hb), ==, 2);
}
diff --git a/util/hbitmap.c b/util/hbitmap.c
index bcc0acdc6a..586920cb52 100644
--- a/util/hbitmap.c
+++ 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));
trace_hbitmap_reset(hb, start, count,
start >> hb->granularity, last >> hb->granularity);
--
2.18.0
next reply other threads:[~2019-08-06 15:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 15:26 Vladimir Sementsov-Ogievskiy [this message]
2019-08-06 16:09 ` [Qemu-devel] [PATCH v2] util/hbitmap: strict hbitmap_reset Max Reitz
2019-08-06 16:19 ` Vladimir Sementsov-Ogievskiy
2019-08-07 16:27 ` John Snow
2019-09-11 15:13 ` Vladimir Sementsov-Ogievskiy
2019-09-11 17:59 ` John Snow
2019-09-12 8:20 ` Vladimir Sementsov-Ogievskiy
2019-09-13 18:49 ` John Snow
2019-09-16 8:00 ` Kevin Wolf
2019-09-16 16:38 ` John Snow
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