block: change default of .has_zero_init to 0

.has_zero_init defaults to 1 for all formats and protocols.

this is a dangerous default since this means that all
new added drivers need to manually overwrite it to 0 if
they do not ensure that a device is zero initialized
after bdrv_create().

if a driver needs to explicitly set this value to
1 its easier to verify the correctness in the review process.

during review of the existing drivers it turned out
that ssh and gluster had a wrong default of 1.
both protocols support host_devices as backend
which are not by default zero initialized. this
wrong assumption will lead to possible corruption
if qemu-img convert is used to write to such a backend.

vpc and vmdk also defaulted to 1 altough they support
fixed respectively flat extends. this has to be addresses
in separate patches. both formats as well as the mentioned
ssh and gluster are turned to the default of 0 with this
patch for safety.

a similar problem with the wrong default existed for
iscsi most likely because the driver developer did
oversee the default value of 1.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -2911,6 +2911,11 @@ void bdrv_flush_all(void)
     }
 }
 
+int bdrv_has_zero_init_1(BlockDriverState *bs)
+{
+    return 1;
+}
+
 int bdrv_has_zero_init(BlockDriverState *bs)
 {
     assert(bs->drv);
@@ -2919,7 +2924,8 @@ int bdrv_has_zero_init(BlockDriverState *bs)
         return bs->drv->bdrv_has_zero_init(bs);
     }
 
-    return 1;
+    /* safe default */
+    return 0;
 }
 
 typedef struct BdrvCoIsAllocatedData {

block/cow.c

@@ -340,6 +340,7 @@ static BlockDriver bdrv_cow = {
     .bdrv_open      = cow_open,
     .bdrv_close     = cow_close,
     .bdrv_create    = cow_create,
+    .bdrv_has_zero_init     = bdrv_has_zero_init_1,
 
     .bdrv_read              = cow_co_read,
     .bdrv_write             = cow_co_write,

block/qcow.c

@@ -892,6 +892,7 @@ static BlockDriver bdrv_qcow = {
     .bdrv_close		= qcow_close,
     .bdrv_reopen_prepare = qcow_reopen_prepare,
     .bdrv_create	= qcow_create,
+    .bdrv_has_zero_init     = bdrv_has_zero_init_1,
 
     .bdrv_co_readv          = qcow_co_readv,
     .bdrv_co_writev         = qcow_co_writev,

block/qcow2.c

@@ -1785,6 +1785,7 @@ static BlockDriver bdrv_qcow2 = {
     .bdrv_close         = qcow2_close,
     .bdrv_reopen_prepare  = qcow2_reopen_prepare,
     .bdrv_create        = qcow2_create,
+    .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_is_allocated = qcow2_co_is_allocated,
     .bdrv_set_key       = qcow2_set_key,
     .bdrv_make_empty    = qcow2_make_empty,

block/qed.c

@@ -1574,6 +1574,7 @@ static BlockDriver bdrv_qed = {
     .bdrv_close               = bdrv_qed_close,
     .bdrv_reopen_prepare      = bdrv_qed_reopen_prepare,
     .bdrv_create              = bdrv_qed_create,
+    .bdrv_has_zero_init       = bdrv_has_zero_init_1,
     .bdrv_co_is_allocated     = bdrv_qed_co_is_allocated,
     .bdrv_make_empty          = bdrv_qed_make_empty,
     .bdrv_aio_readv           = bdrv_qed_aio_readv,

block/raw-posix.c

@@ -1199,6 +1199,7 @@ static BlockDriver bdrv_file = {
     .bdrv_reopen_abort = raw_reopen_abort,
     .bdrv_close = raw_close,
     .bdrv_create = raw_create,
+    .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_is_allocated = raw_co_is_allocated,
 
     .bdrv_aio_readv = raw_aio_readv,
@@ -1527,11 +1528,6 @@ static int hdev_create(const char *filename, QEMUOptionParameter *options)
     return ret;
 }
 
-static int hdev_has_zero_init(BlockDriverState *bs)
-{
-    return 0;
-}
-
 static BlockDriver bdrv_host_device = {
     .format_name        = "host_device",
     .protocol_name        = "host_device",
@@ -1544,7 +1540,6 @@ static BlockDriver bdrv_host_device = {
     .bdrv_reopen_abort   = raw_reopen_abort,
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
-    .bdrv_has_zero_init = hdev_has_zero_init,
 
     .bdrv_aio_readv	= raw_aio_readv,
     .bdrv_aio_writev	= raw_aio_writev,
@@ -1669,7 +1664,6 @@ static BlockDriver bdrv_host_floppy = {
     .bdrv_reopen_abort   = raw_reopen_abort,
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
-    .bdrv_has_zero_init = hdev_has_zero_init,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,
@@ -1771,7 +1765,6 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_reopen_abort   = raw_reopen_abort,
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
-    .bdrv_has_zero_init = hdev_has_zero_init,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,
@@ -1893,7 +1886,6 @@ static BlockDriver bdrv_host_cdrom = {
     .bdrv_reopen_abort   = raw_reopen_abort,
     .bdrv_create        = hdev_create,
     .create_options     = raw_create_options,
-    .bdrv_has_zero_init = hdev_has_zero_init,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,

block/raw-win32.c

@@ -459,6 +459,7 @@ static BlockDriver bdrv_file = {
     .bdrv_file_open	= raw_open,
     .bdrv_close		= raw_close,
     .bdrv_create	= raw_create,
+    .bdrv_has_zero_init = bdrv_has_zero_init_1,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,
@@ -570,11 +571,6 @@ static int hdev_open(BlockDriverState *bs, QDict *options, int flags)
     return 0;
 }
 
-static int hdev_has_zero_init(BlockDriverState *bs)
-{
-    return 0;
-}
-
 static BlockDriver bdrv_host_device = {
     .format_name	= "host_device",
     .protocol_name	= "host_device",
@@ -582,7 +578,6 @@ static BlockDriver bdrv_host_device = {
     .bdrv_probe_device	= hdev_probe_device,
     .bdrv_file_open	= hdev_open,
     .bdrv_close		= raw_close,
-    .bdrv_has_zero_init = hdev_has_zero_init,
 
     .bdrv_aio_readv     = raw_aio_readv,
     .bdrv_aio_writev    = raw_aio_writev,

block/rbd.c

@@ -996,6 +996,7 @@ static BlockDriver bdrv_rbd = {
     .bdrv_file_open     = qemu_rbd_open,
     .bdrv_close         = qemu_rbd_close,
     .bdrv_create        = qemu_rbd_create,
+    .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_get_info      = qemu_rbd_getinfo,
     .create_options     = qemu_rbd_create_options,
     .bdrv_getlength     = qemu_rbd_getlength,

block/sheepdog.c

@@ -2401,6 +2401,7 @@ static BlockDriver bdrv_sheepdog_unix = {
     .bdrv_file_open = sd_open,
     .bdrv_close     = sd_close,
     .bdrv_create    = sd_create,
+    .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_getlength = sd_getlength,
     .bdrv_truncate  = sd_truncate,
 

block/vdi.c

@@ -779,6 +779,7 @@ static BlockDriver bdrv_vdi = {
     .bdrv_close = vdi_close,
     .bdrv_reopen_prepare = vdi_reopen_prepare,
     .bdrv_create = vdi_create,
+    .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_is_allocated = vdi_co_is_allocated,
     .bdrv_make_empty = vdi_make_empty,
 

include/block/block.h

@@ -272,6 +272,7 @@ void bdrv_drain_all(void);
 
 int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);
 int bdrv_co_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);
+int bdrv_has_zero_init_1(BlockDriverState *bs);
 int bdrv_has_zero_init(BlockDriverState *bs);
 int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
                       int *pnum);