Hello,
the attached patch adds support for copy-on-write images: creating them,
deleting them, identifying them.
Mirek
Index: ChangeLog
===================================================================
RCS file: /data/cvs/libvirt/ChangeLog,v
retrieving revision 1.1750
diff -u -p -r1.1750 ChangeLog
--- ChangeLog 8 Dec 2008 13:22:44 -0000 1.1750
+++ ChangeLog 9 Dec 2008 17:25:18 -0000
@@ -1,3 +1,10 @@
+2008-12-09 Miloslav Trmač <mitr@xxxxxxxxxx>
+
+ * src/storage_conf.h, src/storage_conf.c: New volume target option
+ cow-base.
+ * src/storage_backend_fs.c: Implement /volume/target/cow-base.
+ * docs/formatstorage.html.in: Document it.
+
Mon Dec 8 13:22:06 +0100 2008 Jim Meyering <meyering@xxxxxxxxxx>
virsh.c: tweak options to produce more accurate help
Index: docs/formatstorage.html.in
===================================================================
RCS file: /data/cvs/libvirt/docs/formatstorage.html.in,v
retrieving revision 1.5
diff -u -p -r1.5 formatstorage.html.in
--- docs/formatstorage.html.in 4 Dec 2008 14:51:57 -0000 1.5
+++ docs/formatstorage.html.in 9 Dec 2008 17:25:18 -0000
@@ -269,6 +269,13 @@
contains the MAC (eg SELinux) label string.
<span class="since">Since 0.4.1</span>
</dd>
+ <dt><code>cow-base</code></dt>
+ <dd>Provides the key of a base volume. This element is optional, and
+ supported only in some volume types and formats. If it is present,
+ this volume is a copy-on-write volume that stores only changes to the
+ base volume. Changes to the base volume may make this volume
+ inconsistent.
+ </dd>
</dl>
<h2><a name="examples">Example configuration</a></h2>
Index: src/storage_backend_fs.c
===================================================================
RCS file: /data/cvs/libvirt/src/storage_backend_fs.c,v
retrieving revision 1.22
diff -u -p -r1.22 storage_backend_fs.c
--- src/storage_backend_fs.c 17 Nov 2008 11:19:33 -0000 1.22
+++ src/storage_backend_fs.c 9 Dec 2008 17:25:18 -0000
@@ -48,6 +48,18 @@
#include "xml.h"
+enum {
+ GET_COW_BASE_OK,
+ GET_COW_BASE_INVALID,
+ GET_COW_BASE_ERROR,
+};
+
+static int cowGetCowBase(virConnectPtr, char **, const unsigned char *, size_t);
+static int qcowXGetCowBase(virConnectPtr, char **, const unsigned char *,
+ size_t);
+static int vmdk4GetCowBase(virConnectPtr, char **, const unsigned char *,
+ size_t);
+
/* Either 'magic' or 'extension' *must* be provided */
struct FileTypeInfo {
int type; /* One of the constants above */
@@ -64,66 +76,225 @@ struct FileTypeInfo {
* -1 to use st_size as capacity */
int sizeBytes; /* Number of bytes for size field */
int sizeMultiplier; /* A scaling factor if size is not in bytes */
+ /* Store a COW base image path (possibly relative),
+ * or NULL if there is no COW base image, to RES;
+ * return GET_COW_BASE_* */
+ int (*getCowBase)(virConnectPtr conn, char **res, const unsigned char *buf,
+ size_t buf_size);
};
const struct FileTypeInfo const fileTypeInfo[] = {
/* Bochs */
/* XXX Untested
{ VIR_STORAGE_VOL_BOCHS, "Bochs Virtual HD Image", NULL,
__LITTLE_ENDIAN, 64, 0x20000,
- 32+16+16+4+4+4+4+4, 8, 1 },*/
+ 32+16+16+4+4+4+4+4, 8, 1, NULL },*/
/* CLoop */
/* XXX Untested
{ VIR_STORAGE_VOL_CLOOP, "#!/bin/sh\n#V2.0 Format\nmodprobe cloop file=$0 && mount -r -t iso9660 /dev/cloop $1\n", NULL,
__LITTLE_ENDIAN, -1, 0,
- -1, 0, 0 }, */
+ -1, 0, 0, NULL }, */
/* Cow */
{ VIR_STORAGE_VOL_FILE_COW, "OOOM", NULL,
__BIG_ENDIAN, 4, 2,
- 4+4+1024+4, 8, 1 },
+ 4+4+1024+4, 8, 1, cowGetCowBase },
/* DMG */
/* XXX QEMU says there's no magic for dmg, but we should check... */
{ VIR_STORAGE_VOL_FILE_DMG, NULL, ".dmg",
0, -1, 0,
- -1, 0, 0 },
+ -1, 0, 0, NULL },
/* XXX there's probably some magic for iso we can validate too... */
{ VIR_STORAGE_VOL_FILE_ISO, NULL, ".iso",
0, -1, 0,
- -1, 0, 0 },
+ -1, 0, 0, NULL },
/* Parallels */
/* XXX Untested
{ VIR_STORAGE_VOL_FILE_PARALLELS, "WithoutFreeSpace", NULL,
__LITTLE_ENDIAN, 16, 2,
- 16+4+4+4+4, 4, 512 },
+ 16+4+4+4+4, 4, 512, NULL },
*/
/* QCow */
{ VIR_STORAGE_VOL_FILE_QCOW, "QFI", NULL,
__BIG_ENDIAN, 4, 1,
- 4+4+8+4+4, 8, 1 },
+ 4+4+8+4+4, 8, 1, qcowXGetCowBase },
/* QCow 2 */
{ VIR_STORAGE_VOL_FILE_QCOW2, "QFI", NULL,
__BIG_ENDIAN, 4, 2,
- 4+4+8+4+4, 8, 1 },
+ 4+4+8+4+4, 8, 1, qcowXGetCowBase },
/* VMDK 3 */
/* XXX Untested
{ VIR_STORAGE_VOL_FILE_VMDK, "COWD", NULL,
__LITTLE_ENDIAN, 4, 1,
- 4+4+4, 4, 512 },
+ 4+4+4, 4, 512, NULL },
*/
/* VMDK 4 */
{ VIR_STORAGE_VOL_FILE_VMDK, "KDMV", NULL,
__LITTLE_ENDIAN, 4, 1,
- 4+4+4, 8, 512 },
+ 4+4+4, 8, 512, vmdk4GetCowBase },
/* Connectix / VirtualPC */
/* XXX Untested
{ VIR_STORAGE_VOL_FILE_VPC, "conectix", NULL,
__BIG_ENDIAN, -1, 0,
- -1, 0, 0},
+ -1, 0, 0, NULL},
*/
};
+static const struct FileTypeInfo *
+virStorageBackendFileSystemVolFormatToInfo(virConnectPtr conn, int format)
+{
+ size_t i;
+
+ for (i = 0; i < sizeof(fileTypeInfo) / sizeof(fileTypeInfo[0]); i++) {
+ if (fileTypeInfo[i].type == format)
+ return &fileTypeInfo[i];
+ }
+
+ virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
+ _("unsupported volume format %d"), format);
+ return NULL;
+}
+
+static int
+cowGetCowBase(virConnectPtr conn,
+ char **res,
+ const unsigned char *buf,
+ size_t buf_size)
+{
+ size_t len;
+
+ *res = NULL;
+ if (buf_size < 4+4+1024)
+ return GET_COW_BASE_INVALID;
+ if (buf[4+4] == '\0')
+ return GET_COW_BASE_OK;
+
+ len = 1024;
+ if (VIR_ALLOC_N(*res, len + 1) < 0) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY,
+ _("copy-on-write base path"));
+ return GET_COW_BASE_ERROR;
+ }
+ memcpy(*res, buf + 4+4, len);
+ (*res)[len] = '\0';
+ if (VIR_REALLOC_N(*res, strlen(*res) + 1) < 0) {
+ /* Ignore failure */
+ }
+ return GET_COW_BASE_OK;
+}
+
+static int
+qcowXGetCowBase(virConnectPtr conn,
+ char **res,
+ const unsigned char *buf,
+ size_t buf_size)
+{
+ unsigned long long offset;
+ unsigned long size;
+
+ *res = NULL;
+ if (buf_size < 4+4+8+4)
+ return GET_COW_BASE_INVALID;
+ offset = (((unsigned long long)buf[4+4] << 56)
+ | ((unsigned long long)buf[4+4+1] << 48)
+ | ((unsigned long long)buf[4+4+2] << 40)
+ | ((unsigned long long)buf[4+4+3] << 32)
+ | ((unsigned long long)buf[4+4+4] << 24)
+ | ((unsigned long long)buf[4+4+5] << 16)
+ | ((unsigned long long)buf[4+4+6] << 8)
+ | buf[4+4+7]);
+ if (offset > buf_size)
+ return GET_COW_BASE_INVALID;
+ size = ((buf[4+4+8] << 24)
+ | (buf[4+4+8+1] << 16)
+ | (buf[4+4+8+2] << 8)
+ | buf[4+4+8+3]);
+ if (size == 0)
+ return GET_COW_BASE_OK;
+ if (offset + size > buf_size || offset + size < offset)
+ return GET_COW_BASE_INVALID;
+ if (size + 1 == 0)
+ return GET_COW_BASE_INVALID;
+ if (VIR_ALLOC_N(*res, size + 1) < 0) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY,
+ _("copy-on-write base path"));
+ return GET_COW_BASE_ERROR;
+ }
+ memcpy(*res, buf + offset, size);
+ (*res)[size] = '\0';
+ return GET_COW_BASE_OK;
+}
+
+static int
+vmdk4GetCowBase(virConnectPtr conn,
+ char **res,
+ const unsigned char *buf,
+ size_t buf_size)
+{
+ static const char prefix[] = "parentFileNameHint=\"";
+
+ char desc[20*512 + 1], *start, *end;
+ size_t len;
+
+ *res = NULL;
+ if (buf_size <= 0x200)
+ return GET_COW_BASE_INVALID;
+ /* FIXME? the default buf_size is not large enough to contain the complete
+ descriptor. */
+ len = buf_size - 0x200;
+ if (len > sizeof(desc) - 1)
+ len = sizeof(desc) - 1;
+ memcpy(desc, buf + 0x200, len);
+ desc[len] = '\0';
+ start = strstr(desc, prefix);
+ if (start == NULL)
+ return GET_COW_BASE_OK;
+ start += strlen(prefix);
+ end = strchr(start, '"');
+ if (end == NULL)
+ return GET_COW_BASE_INVALID;
+ if (end == start)
+ return GET_COW_BASE_OK;
+ *end = '\0';
+ *res = strdup(start);
+ if (*res == NULL) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY,
+ _("copy-on-write base path"));
+ return GET_COW_BASE_ERROR;
+ }
+ return GET_COW_BASE_OK;
+}
+
+/**
+ * Return an absolute path corresponding to PATH, which is absolute or relative
+ * to the directory containing BASE_FILE, or NULL on error
+ */
+static char *absolutePathFromBaseFile(const char *base_file, const char *path)
+{
+ size_t base_size, path_size;
+ char *res, *p;
+
+ if (*path == '/')
+ return strdup(path);
+
+ base_size = strlen(base_file) + 1;
+ path_size = strlen(path) + 1;
+ if (VIR_ALLOC_N(res, base_size - 1 + path_size) < 0)
+ return NULL;
+ memcpy(res, base_file, base_size);
+ p = strrchr(res, '/');
+ if (p != NULL)
+ p++;
+ else
+ p = res;
+ memcpy(p, path, path_size);
+ if (VIR_REALLOC_N(res, (p + path_size) - res) < 0) {
+ /* Ignore failure */
+ }
+ return res;
+}
+
/**
* Probe the header of a file to determine what type of disk image
* it is, and info about its capacity if available.
@@ -219,6 +390,32 @@ static int virStorageBackendProbeFile(vi
/* Validation passed, we know the file format now */
def->target.format = fileTypeInfo[i].type;
+ if (fileTypeInfo[i].getCowBase != NULL) {
+ char *base;
+
+ switch (fileTypeInfo[i].getCowBase(conn, &base, head, len)) {
+ case GET_COW_BASE_OK:
+ break;
+
+ case GET_COW_BASE_INVALID:
+ continue;
+
+ case GET_COW_BASE_ERROR:
+ return -1;
+ }
+ if (base == NULL)
+ def->target.cowBase = NULL;
+ else {
+ def->target.cowBase = absolutePathFromBaseFile(def->target.path,
+ base);
+ free(base);
+ if (def->target.cowBase == NULL) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY,
+ _("copy-on-write base path"));
+ return -1;
+ }
+ }
+ }
return 0;
}
@@ -832,7 +1029,9 @@ virStorageBackendFileSystemVolCreate(vir
#if HAVE_QEMU_IMG
const char *type;
char size[100];
- const char *imgargv[7];
+ const char *imgargv[9];
+ size_t i;
+ virStorageVolDefPtr cowBase;
if ((type = virStorageVolFormatFileSystemTypeToString(vol->target.format)) == NULL) {
virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
@@ -840,17 +1039,55 @@ virStorageBackendFileSystemVolCreate(vir
vol->target.format);
return -1;
}
+ if (vol->target.cowBase == NULL)
+ cowBase = NULL;
+ else {
+ const struct FileTypeInfo *info;
+
+ info = virStorageBackendFileSystemVolFormatToInfo(conn,
+ vol->target.format);
+ if (info == NULL) {
+ virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
+ _("unknown storage vol type %d"),
+ vol->target.format);
+ return -1;
+ }
+ if (info->getCowBase == NULL) {
+ virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
+ _("copy-on-write not supported with "
+ "format %s"), type);
+ return -1;
+ }
+ cowBase = virStorageVolDefFindByKey(pool, vol->target.cowBase);
+ if (cowBase == NULL) {
+ virStorageReportError(conn, VIR_ERR_NO_STORAGE_VOL,
+ _("unknown copy-on-write base volume "
+ "key %s"), vol->target.cowBase);
+ return -1;
+ }
+ if (cowBase->target.format != vol->target.format) {
+ virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
+ _("copy-on-write with mixed file formats "
+ "not supported"));
+ return -1;
+ }
+ }
/* Size in KB */
snprintf(size, sizeof(size), "%llu", vol->capacity/1024);
- imgargv[0] = QEMU_IMG;
- imgargv[1] = "create";
- imgargv[2] = "-f";
- imgargv[3] = type;
- imgargv[4] = vol->target.path;
- imgargv[5] = size;
- imgargv[6] = NULL;
+ i = 0;
+ imgargv[i++] = QEMU_IMG;
+ imgargv[i++] = "create";
+ imgargv[i++] = "-f";
+ imgargv[i++] = type;
+ if (cowBase != NULL) {
+ imgargv[i++] = "-b";
+ imgargv[i++] = cowBase->target.path;
+ }
+ imgargv[i++] = vol->target.path;
+ imgargv[i++] = size;
+ imgargv[i++] = NULL;
if (virRun(conn, imgargv, NULL) < 0) {
unlink(vol->target.path);
@@ -878,6 +1115,12 @@ virStorageBackendFileSystemVolCreate(vir
vol->target.format);
return -1;
}
+ if (vol->target.cowBase != NULL) {
+ virStorageReportError(conn, VIR_ERR_NO_SUPPORT,
+ _("copy-on-write image not supported with "
+ "qcow-create"));
+ return -1;
+ }
/* Size in MB - yes different units to qemu-img :-( */
snprintf(size, sizeof(size), "%llu", vol->capacity/1024/1024);
@@ -951,10 +1194,23 @@ virStorageBackendFileSystemVolCreate(vir
*/
static int
virStorageBackendFileSystemVolDelete(virConnectPtr conn,
- virStoragePoolObjPtr pool ATTRIBUTE_UNUSED,
+ virStoragePoolObjPtr pool,
virStorageVolDefPtr vol,
unsigned int flags ATTRIBUTE_UNUSED)
{
+ size_t i;
+
+ for (i = 0; i < pool->volumes.count; i++) {
+ const char *cowBase;
+
+ cowBase = pool->volumes.objs[i]->target.cowBase;
+ if (cowBase != NULL && STREQ(cowBase, vol->key)) {
+ virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
+ _("volume %s is used by volume %s"),
+ vol->key, pool->volumes.objs[i]->key);
+ return -1;
+ }
+ }
if (unlink(vol->target.path) < 0) {
/* Silently ignore failures where the vol has already gone away */
if (errno != ENOENT) {
Index: src/storage_conf.c
===================================================================
RCS file: /data/cvs/libvirt/src/storage_conf.c,v
retrieving revision 1.33
diff -u -p -r1.33 storage_conf.c
--- src/storage_conf.c 8 Dec 2008 11:28:37 -0000 1.33
+++ src/storage_conf.c 9 Dec 2008 17:25:18 -0000
@@ -247,6 +247,7 @@ virStorageVolDefFree(virStorageVolDefPtr
VIR_FREE(def->target.path);
VIR_FREE(def->target.perms.label);
+ VIR_FREE(def->target.cowBase);
VIR_FREE(def);
}
@@ -993,6 +994,10 @@ virStorageVolDefParseDoc(virConnectPtr c
if (virStorageVolDefParsePerms(conn, ctxt, &ret->target.perms) < 0)
goto cleanup;
+ ret->target.cowBase = virXPathString(conn,
+ "string(/volume/target/cow-base)",
+ ctxt);
+
return ret;
cleanup:
@@ -1141,6 +1146,10 @@ virStorageVolDefFormat(virConnectPtr con
def->target.perms.label);
virBufferAddLit(&buf," </permissions>\n");
+
+ if (def->target.cowBase)
+ virBufferVSprintf(&buf, " <cow-base>%s</cow-base>\n",
+ def->target.cowBase);
virBufferAddLit(&buf, " </target>\n");
virBufferAddLit(&buf,"</volume>\n");
Index: src/storage_conf.h
===================================================================
RCS file: /data/cvs/libvirt/src/storage_conf.h,v
retrieving revision 1.13
diff -u -p -r1.13 storage_conf.h
--- src/storage_conf.h 4 Dec 2008 22:00:14 -0000 1.13
+++ src/storage_conf.h 9 Dec 2008 17:25:18 -0000
@@ -73,6 +73,7 @@ struct _virStorageVolTarget {
char *path;
int format;
virStoragePerms perms;
+ char *cowBase;
};
--
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