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qcow2: Store data file name in the image
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Rather than requiring that the external data file node is passed
explicitly when creating the qcow2 node, store the filename in the
designated header extension during .bdrv_create and read it from there
as a default during .bdrv_open.

Signed-off-by: Kevin Wolf <[email protected]>
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@kevmw
kevmw committed Mar 8, 2019
1 parent dcc9868 commit 9b890bd
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Showing 4 changed files with 128 additions and 2 deletions.
94 changes: 93 additions & 1 deletion block/qcow2.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -398,6 +398,21 @@ static int qcow2_read_extensions(BlockDriverState *bs, uint64_t start_offset,
#endif
break;

case QCOW2_EXT_MAGIC_DATA_FILE:
{
s->image_data_file = g_malloc0(ext.len + 1);
ret = bdrv_pread(bs->file, offset, s->image_data_file, ext.len);
if (ret < 0) {
error_setg_errno(errp, -ret,
"ERROR: Could not read data file name");
return ret;
}
#ifdef DEBUG_EXT
printf("Qcow2: Got external data file %s\n", s->image_data_file);
#endif
break;
}

default:
/* unknown magic - save it in case we need to rewrite the header */
/* If you add a new feature, make sure to also update the fast
Expand Down Expand Up @@ -1463,6 +1478,15 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
}

if (s->incompatible_features & QCOW2_INCOMPAT_DATA_FILE) {
if (!s->data_file && s->image_data_file) {
s->data_file = bdrv_open_child(s->image_data_file, options,
"data-file", bs, &child_file,
false, errp);
if (!s->data_file) {
ret = -EINVAL;
goto fail;
}
}
if (!s->data_file) {
error_setg(errp, "'data-file' is required for this image");
ret = -EINVAL;
Expand Down Expand Up @@ -1650,6 +1674,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
return ret;

fail:
g_free(s->image_data_file);
if (has_data_file(bs)) {
bdrv_unref_child(bs, s->data_file);
}
Expand Down Expand Up @@ -2269,6 +2294,7 @@ static void qcow2_close(BlockDriverState *bs)
g_free(s->unknown_header_fields);
cleanup_unknown_header_ext(bs);

g_free(s->image_data_file);
g_free(s->image_backing_file);
g_free(s->image_backing_format);

Expand Down Expand Up @@ -2445,6 +2471,19 @@ int qcow2_update_header(BlockDriverState *bs)
buflen -= ret;
}

/* External data file header extension */
if (has_data_file(bs) && s->image_data_file) {
ret = header_ext_add(buf, QCOW2_EXT_MAGIC_DATA_FILE,
s->image_data_file, strlen(s->image_data_file),
buflen);
if (ret < 0) {
goto fail;
}

buf += ret;
buflen -= ret;
}

/* Full disk encryption header pointer extension */
if (s->crypto_header.offset != 0) {
s->crypto_header.offset = cpu_to_be64(s->crypto_header.offset);
Expand Down Expand Up @@ -3086,6 +3125,12 @@ qcow2_co_create(BlockdevCreateOptions *create_options, Error **errp)
abort();
}

/* Set the external data file if necessary */
if (data_bs) {
BDRVQcow2State *s = blk_bs(blk)->opaque;
s->image_data_file = g_strdup(data_bs->filename);
}

/* Create a full header (including things like feature table) */
ret = qcow2_update_header(blk_bs(blk));
if (ret < 0) {
Expand Down Expand Up @@ -3165,6 +3210,7 @@ static int coroutine_fn qcow2_co_create_opts(const char *filename, QemuOpts *opt
QDict *qdict;
Visitor *v;
BlockDriverState *bs = NULL;
BlockDriverState *data_bs = NULL;
Error *local_err = NULL;
const char *val;
int ret;
Expand Down Expand Up @@ -3228,6 +3274,26 @@ static int coroutine_fn qcow2_co_create_opts(const char *filename, QemuOpts *opt
goto finish;
}

/* Create and open an external data file (protocol layer) */
val = qdict_get_try_str(qdict, BLOCK_OPT_DATA_FILE);
if (val) {
ret = bdrv_create_file(val, opts, errp);
if (ret < 0) {
goto finish;
}

data_bs = bdrv_open(val, NULL, NULL,
BDRV_O_RDWR | BDRV_O_RESIZE | BDRV_O_PROTOCOL,
errp);
if (data_bs == NULL) {
ret = -EIO;
goto finish;
}

qdict_del(qdict, BLOCK_OPT_DATA_FILE);
qdict_put_str(qdict, "data-file", data_bs->node_name);
}

/* Set 'driver' and 'node' options */
qdict_put_str(qdict, "driver", "qcow2");
qdict_put_str(qdict, "file", bs->node_name);
Expand Down Expand Up @@ -3262,6 +3328,7 @@ static int coroutine_fn qcow2_co_create_opts(const char *filename, QemuOpts *opt
finish:
qobject_unref(qdict);
bdrv_unref(bs);
bdrv_unref(data_bs);
qapi_free_BlockdevCreateOptions(create_options);
return ret;
}
Expand Down Expand Up @@ -4552,6 +4619,8 @@ static ImageInfoSpecific *qcow2_get_specific_info(BlockDriverState *bs,
.refcount_bits = s->refcount_bits,
.has_bitmaps = !!bitmaps,
.bitmaps = bitmaps,
.has_data_file = !!s->image_data_file,
.data_file = g_strdup(s->image_data_file),
};
} else {
/* if this assertion fails, this probably means a new version was
Expand Down Expand Up @@ -4754,7 +4823,7 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
BDRVQcow2State *s = bs->opaque;
int old_version = s->qcow_version, new_version = old_version;
uint64_t new_size = 0;
const char *backing_file = NULL, *backing_format = NULL;
const char *backing_file = NULL, *backing_format = NULL, *data_file = NULL;
bool lazy_refcounts = s->use_lazy_refcounts;
const char *compat = NULL;
uint64_t cluster_size = s->cluster_size;
Expand Down Expand Up @@ -4836,6 +4905,13 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
"may not exceed 64 bits");
return -EINVAL;
}
} else if (!strcmp(desc->name, BLOCK_OPT_DATA_FILE)) {
data_file = qemu_opt_get(opts, BLOCK_OPT_DATA_FILE);
if (data_file && !has_data_file(bs)) {
error_setg(errp, "data-file can only be set for images that "
"use an external data file");
return -EINVAL;
}
} else {
/* if this point is reached, this probably means a new option was
* added without having it covered here */
Expand Down Expand Up @@ -4882,6 +4958,17 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
}
}

if (data_file) {
g_free(s->image_data_file);
s->image_data_file = *data_file ? g_strdup(data_file) : NULL;
}

ret = qcow2_update_header(bs);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to update the image header");
return ret;
}

if (backing_file || backing_format) {
ret = qcow2_change_backing_file(bs,
backing_file ?: s->image_backing_file,
Expand Down Expand Up @@ -5029,6 +5116,11 @@ static QemuOptsList qcow2_create_opts = {
.type = QEMU_OPT_STRING,
.help = "Image format of the base image"
},
{
.name = BLOCK_OPT_DATA_FILE,
.type = QEMU_OPT_STRING,
.help = "File name of an external data file"
},
{
.name = BLOCK_OPT_ENCRYPT,
.type = QEMU_OPT_BOOL,
Expand Down
1 change: 1 addition & 0 deletions block/qcow2.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -343,6 +343,7 @@ typedef struct BDRVQcow2State {
* override) */
char *image_backing_file;
char *image_backing_format;
char *image_data_file;

CoQueue compress_wait_queue;
int nb_compress_threads;
Expand Down
8 changes: 7 additions & 1 deletion qapi/block-core.json
View file
Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,9 @@
#
# @compat: compatibility level
#
# @data-file: the filename of the external data file that is stored in the
# image and used as a default for opening the image (since: 4.0)
#
# @lazy-refcounts: on or off; only valid for compat >= 1.1
#
# @corrupt: true if the image has been marked corrupt; only valid for
Expand All @@ -76,6 +79,7 @@
{ 'struct': 'ImageInfoSpecificQCow2',
'data': {
'compat': 'str',
'*data-file': 'str',
'*lazy-refcounts': 'bool',
'*corrupt': 'bool',
'refcount-bits': 'int',
Expand Down Expand Up @@ -3082,7 +3086,9 @@
#
# @data-file: reference to or definition of the external data file.
# This may only be specified for images that require an
# external data file. (since 4.0)
# external data file. If it is not specified for such
# an image, the data file name is loaded from the image
# file. (since 4.0)
#
# Since: 2.9
##
Expand Down
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