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block: change default of .has_zero_init to 0

PATCH Applied Peter Lieven 2 participants 2 messages Jun 28, 2013 Block layer

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Peter Lieven

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#0 lore raw

PATCH v2 1/1 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 <[email protected]>

---
v1->v2:
- fixed typos
- removed bdrv_has_zero_init_1 for vpc and vmdk
- added bdrv_has_zero_init_1 for cow

 block.c               |    8 +++++++-
 block/cow.c           |    1 +
 block/qcow.c          |    1 +
 block/qcow2.c         |    1 +
 block/qed.c           |    1 +
 block/raw-posix.c     |   10 +---------
 block/raw-win32.c     |    7 +------
 block/rbd.c           |    1 +
 block/sheepdog.c      |    1 +
 block/vdi.c           |    1 +
 include/block/block.h |    1 +
 11 files changed, 17 insertions(+), 16 deletions(-)
block.c +7 -1
index 8e77d46..80f72dc 100644
@@ -2916,6 +2916,11 @@ 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);

@@ -2924,7 +2929,8 @@ 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 +1 -0
index 9f94599..1cc2e89 100644
@@ -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 +1 -0
index e2a64c7..5239bd6 100644
@@ -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 +1 -0
index 9383990..0eceefe 100644
@@ -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 +1 -0
index 4651403..f767b05 100644
@@ -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 +1 -9
index c0ccf27..8597d77 100644
@@ -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,

@@ -1526,11 +1527,6 @@ 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",

@@ -1543,7 +1539,6 @@ 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,

@@ -1668,7 +1663,6 @@ 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,

@@ -1770,7 +1764,6 @@ 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,

@@ -1892,7 +1885,6 @@ 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 +1 -6
index 7c03b6d..9b5b2af 100644
@@ -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 +1 -0
index 0f2608b..cb71751 100644
@@ -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 +1 -0
index 1b7c3f1..b397b5b 100644
@@ -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 +1 -0
index 2662d89..8a91525 100644
@@ -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 +1 -0
index 2307f67..dd8eca1 100644
@@ -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);
Signature · 1 line
1.7.9.5
Applied
#1 lore raw

Am 28.06.2013 um 12:47 hat Peter Lieven geschrieben:

Quoted 27 lines

.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.

Quoted 6 lines
Signed-off-by Peter Lieven <[email protected]>

---
v1->v2:
- fixed typos
- removed bdrv_has_zero_init_1 for vpc and vmdk
- added bdrv_has_zero_init_1 for cow

Thanks, applied to the block branch.

Kevin