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stream: do not copy unallocated sectors from the base 

Unallocated sectors should really never be accessed by the guest,
so there's no need to copy them during the streaming process.
If they are read by the guest during streaming, guest-initiated
copy-on-read will copy them (we're in the base == NULL case, which
enables copy on read).  If they are read after we disconnect the
image from the base, they will read as zeroes anyway.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2012-05-08 16:51:58 +02:00 committed by Kevin Wolf
parent b21d677ee9
commit efcc7a2324
2 changed files with 7 additions and 16 deletions
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18
block/stream.c
View File

@ -130,14 +130,9 @@ static int coroutine_fn is_allocated_base(BlockDriverState *top,
*/
intermediate = top->backing_hd;
while (intermediate) {
while (intermediate != base) {
int pnum_inter;
/* reached base */
if (intermediate == base) {
*pnum = n;
return 1;
}
ret = bdrv_co_is_allocated(intermediate, sector_num, nb_sectors,
&pnum_inter);
if (ret < 0) {
@ -160,6 +155,7 @@ static int coroutine_fn is_allocated_base(BlockDriverState *top,
intermediate = intermediate->backing_hd;
}
*pnum = n;
return 1;
}
@ -203,14 +199,8 @@ wait:
break;
}
if (base) {
ret = is_allocated_base(bs, base, sector_num,
STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
} else {
ret = bdrv_co_is_allocated(bs, sector_num,
STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE,
&n);
}
ret = is_allocated_base(bs, base, sector_num,
STREAM_BUFFER_SIZE / BDRV_SECTOR_SIZE, &n);
trace_stream_one_iteration(s, sector_num, n, ret);
if (ret == 0) {
if (s->common.speed) {

5
tests/qemu-iotests/030
View File

@ -83,8 +83,9 @@ class TestSingleDrive(ImageStreamingTestCase):
self.assert_no_active_streams()
self.vm.shutdown()
self.assertFalse('sectors not allocated' in qemu_io('-c', 'map', test_img),
'image file not fully populated after streaming')
self.assertEqual(qemu_io('-c', 'map', backing_img),
qemu_io('-c', 'map', test_img),
'image file map does not match backing file after streaming')
def test_stream_partial(self):
self.assert_no_active_streams()