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qcow2: Add keep_data_file command-line option

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Add a command-line-only option to prevent overwriting the file specified
as external data file.

This option is only available on the qemu-img create command line, not
via blockdev-create, as it makes no sense there: That interface
separates file creation and formatting, so where the external data file
attached to a newly formatted qcow2 node comes from is completely up to
the user.

Implementation detail: Enabling this option will not only not overwrite
the external data file, but also assume it already exists, for two
reasons:
- It is simpler than checking whether the file exists, and only skipping
  creating it when it does not.  It is therefore also less error-prone,
  i.e. we can never accidentally overwrite an existing file because we
  made some mistake in checking whether it exists.
- I think it makes sense from a user's perspective: You set this option
  when you want to use an existing data file, and you unset it when you
  want a new one.  Getting an error when you expect to use an existing
  data file seems to me a nice warning that something is not right.

Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20250530084448.192369-2-hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[kwolf: Removed redundant has_data_file_raw check]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Hanna Czenczek
2025-05-30 10:44:44 +02:00
committed by Kevin Wolf
parent 1d6610099b
commit 910451bc5b
3 changed files with 87 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

72
block/qcow2.c
View File

@@ -3991,6 +3991,8 @@ qcow2_co_create_opts(BlockDriver *drv, const char *filename, QemuOpts *opts,
BlockDriverState *bs = NULL;
BlockDriverState *data_bs = NULL;
const char *val;
bool keep_data_file = false;
BlockdevCreateOptionsQcow2 *qcow2_opts;
int ret;
/* Only the keyval visitor supports the dotted syntax needed for
@@ -4022,6 +4024,22 @@ qcow2_co_create_opts(BlockDriver *drv, const char *filename, QemuOpts *opts,
qdict_put_str(qdict, BLOCK_OPT_COMPAT_LEVEL, "v3");
}
val = qdict_get_try_str(qdict, BLOCK_OPT_KEEP_DATA_FILE);
if (val) {
if (!strcmp(val, "on")) {
keep_data_file = true;
} else if (!strcmp(val, "off")) {
keep_data_file = false;
} else {
error_setg(errp,
"Invalid value '%s' for '%s': Must be 'on' or 'off'",
val, BLOCK_OPT_KEEP_DATA_FILE);
ret = -EINVAL;
goto finish;
}
qdict_del(qdict, BLOCK_OPT_KEEP_DATA_FILE);
}
/* Change legacy command line options into QMP ones */
static const QDictRenames opt_renames[] = {
{ BLOCK_OPT_BACKING_FILE, "backing-file" },
@@ -4058,9 +4076,11 @@ qcow2_co_create_opts(BlockDriver *drv, const char *filename, QemuOpts *opts,
/* Create and open an external data file (protocol layer) */
val = qdict_get_try_str(qdict, BLOCK_OPT_DATA_FILE);
if (val) {
ret = bdrv_co_create_file(val, opts, false, errp);
if (ret < 0) {
goto finish;
if (!keep_data_file) {
ret = bdrv_co_create_file(val, opts, false, errp);
if (ret < 0) {
goto finish;
}
}
data_bs = bdrv_co_open(val, NULL, NULL,
@@ -4073,6 +4093,11 @@ qcow2_co_create_opts(BlockDriver *drv, const char *filename, QemuOpts *opts,
qdict_del(qdict, BLOCK_OPT_DATA_FILE);
qdict_put_str(qdict, "data-file", data_bs->node_name);
} else if (keep_data_file) {
error_setg(errp, "Must not use '%s=on' without '%s'",
BLOCK_OPT_KEEP_DATA_FILE, BLOCK_OPT_DATA_FILE);
ret = -EINVAL;
goto finish;
}
/* Set 'driver' and 'node' options */
@@ -4093,6 +4118,37 @@ qcow2_co_create_opts(BlockDriver *drv, const char *filename, QemuOpts *opts,
goto finish;
}
qcow2_opts = &create_options->u.qcow2;
if (!qcow2_opts->has_preallocation) {
qcow2_opts->preallocation = PREALLOC_MODE_OFF;
}
if (keep_data_file &&
qcow2_opts->preallocation != PREALLOC_MODE_OFF &&
qcow2_opts->preallocation != PREALLOC_MODE_METADATA)
{
error_setg(errp, "Preallocating more than only metadata would "
"overwrite the external data file's content and is "
"therefore incompatible with '%s=on'",
BLOCK_OPT_KEEP_DATA_FILE);
ret = -EINVAL;
goto finish;
}
if (keep_data_file &&
qcow2_opts->preallocation == PREALLOC_MODE_OFF &&
!qcow2_opts->data_file_raw)
{
error_setg(errp, "'%s=on' requires '%s=metadata' or '%s=on', or the "
"file contents will not be visible",
BLOCK_OPT_KEEP_DATA_FILE,
BLOCK_OPT_PREALLOC,
BLOCK_OPT_DATA_FILE_RAW);
ret = -EINVAL;
goto finish;
}
/* Silently round up size */
create_options->u.qcow2.size = ROUND_UP(create_options->u.qcow2.size,
BDRV_SECTOR_SIZE);
@@ -4103,7 +4159,9 @@ finish:
if (ret < 0) {
bdrv_graph_co_rdlock();
bdrv_co_delete_file_noerr(bs);
bdrv_co_delete_file_noerr(data_bs);
if (!keep_data_file) {
bdrv_co_delete_file_noerr(data_bs);
}
bdrv_graph_co_rdunlock();
} else {
ret = 0;
@@ -6202,6 +6260,12 @@ static QemuOptsList qcow2_create_opts = {
.help = "Compression method used for image cluster " \
"compression", \
.def_value_str = "zlib" \
}, \
{ \
.name = BLOCK_OPT_KEEP_DATA_FILE, \
.type = QEMU_OPT_BOOL, \
.help = "Assume the external data file already exists and " \
"do not overwrite it" \
},
QCOW_COMMON_OPTIONS,
{ /* end of list */ }

1
include/block/block_int-common.h
View File

@@ -56,6 +56,7 @@
#define BLOCK_OPT_DATA_FILE_RAW "data_file_raw"
#define BLOCK_OPT_COMPRESSION_TYPE "compression_type"
#define BLOCK_OPT_EXTL2 "extended_l2"
#define BLOCK_OPT_KEEP_DATA_FILE "keep_data_file"
#define BLOCK_PROBE_BUF_SIZE 512

18
tests/qemu-iotests/082.out
View File

@@ -66,6 +66,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -92,6 +93,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -118,6 +120,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -144,6 +147,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -170,6 +174,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -196,6 +201,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -222,6 +228,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -248,6 +255,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -288,6 +296,7 @@ Supported qcow2 options:
encrypt.key-secret=<str> - ID of secret providing qcow AES key or LUKS passphrase
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
refcount_bits=<num> - Width of a reference count entry in bits
@@ -376,6 +385,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -402,6 +412,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -428,6 +439,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -454,6 +466,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -480,6 +493,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -506,6 +520,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -532,6 +547,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -558,6 +574,7 @@ Supported options:
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
extent_size_hint=<size> - Extent size hint for the image file, 0 to disable
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
nocow=<bool (on/off)> - Turn off copy-on-write (valid only on btrfs)
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
@@ -598,6 +615,7 @@ Supported qcow2 options:
encrypt.key-secret=<str> - ID of secret providing qcow AES key or LUKS passphrase
encryption=<bool (on/off)> - Encrypt the image with format 'aes'. (Deprecated in favor of encrypt.format=aes)
extended_l2=<bool (on/off)> - Extended L2 tables
keep_data_file=<bool (on/off)> - Assume the external data file already exists and do not overwrite it
lazy_refcounts=<bool (on/off)> - Postpone refcount updates
preallocation=<str> - Preallocation mode (allowed values: off, metadata, falloc, full)
refcount_bits=<num> - Width of a reference count entry in bits