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qcow2: Fix .bdrv_has_zero_init() 

If a qcow2 file is preallocated, it can no longer guarantee that it
initially appears as filled with zeroes.

So implement .bdrv_has_zero_init() by checking whether the file is
preallocated; if so, forward the call to the underlying storage node,
except for when it is encrypted: Encrypted preallocated images always
return effectively random data, so .bdrv_has_zero_init() must always
return 0 for them.

.bdrv_has_zero_init_truncate() can remain bdrv_has_zero_init_1(),
because it presupposes PREALLOC_MODE_OFF.

Reported-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190724171239.8764-7-mreitz@redhat.com
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2019-07-24 19:12:34 +02:00
parent b647d69adc
commit 38841dcd27
1 changed files with 28 additions and 1 deletions
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29
block/qcow2.c
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@ -4632,6 +4632,33 @@ static ImageInfoSpecific *qcow2_get_specific_info(BlockDriverState *bs,
return spec_info;
}
static int qcow2_has_zero_init(BlockDriverState *bs)
{
BDRVQcow2State *s = bs->opaque;
bool preallocated;
if (qemu_in_coroutine()) {
qemu_co_mutex_lock(&s->lock);
}
/*
* Check preallocation status: Preallocated images have all L2
* tables allocated, nonpreallocated images have none. It is
* therefore enough to check the first one.
*/
preallocated = s->l1_size > 0 && s->l1_table[0] != 0;
if (qemu_in_coroutine()) {
qemu_co_mutex_unlock(&s->lock);
}
if (!preallocated) {
return 1;
} else if (bs->encrypted) {
return 0;
} else {
return bdrv_has_zero_init(s->data_file->bs);
}
}
static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t pos)
{
@ -5187,7 +5214,7 @@ BlockDriver bdrv_qcow2 = {
.bdrv_child_perm = bdrv_format_default_perms,
.bdrv_co_create_opts = qcow2_co_create_opts,
.bdrv_co_create = qcow2_co_create,
.bdrv_has_zero_init = bdrv_has_zero_init_1,
.bdrv_has_zero_init = qcow2_has_zero_init,
.bdrv_has_zero_init_truncate = bdrv_has_zero_init_1,
.bdrv_co_block_status = qcow2_co_block_status,