Commit 38841dcd authored by Max Reitz's avatar Max Reitz
Browse files

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: default avatarStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Message-id: 20190724171239.8764-7-mreitz@redhat.com
Reviewed-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent b647d69a

block/qcow2.c

+28 −1
Original line number Diff line number Diff line
@@ -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,