Daniel,
thanks for the review.
The attached patch should fix everything you pointed out, except for
this comment:
Daniel P. Berrange píše v St 10. 12. 2008 v 17:58 +0000:
> > +
> > +/**
> > + * 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;
> > +}
>
> Seeems like we could just call libc 'realpath' function here ?
realpath() is relative to the current directory, not to "path".
Mirek
Index: ChangeLog
===================================================================
RCS file: /data/cvs/libvirt/ChangeLog,v
retrieving revision 1.1775
diff -u -r1.1775 ChangeLog
--- ChangeLog 15 Dec 2008 11:00:11 -0000 1.1775
+++ ChangeLog 15 Dec 2008 14:51:31 -0000
@@ -1,3 +1,10 @@
+2008-12-15 Miloslav Trmač <mitr@xxxxxxxxxx>
+
+ * src/storage_conf.h, src/storage_conf.c: New volume target option
+ backingstore.
+ * src/storage_backend_fs.c: Implement /volume/target/backingstore.
+ * docs/formatstorage.html.in: Document it.
+
Mon Dec 15 10:59:19 GMT 2008 Daniel P. Berrange <berrange@xxxxxxxxxx>
* src/domain_conf.c: Unlock domain object after fetching
Index: docs/formatstorage.html.in
===================================================================
RCS file: /data/cvs/libvirt/docs/formatstorage.html.in,v
retrieving revision 1.5
diff -u -r1.5 formatstorage.html.in
--- docs/formatstorage.html.in 4 Dec 2008 14:51:57 -0000 1.5
+++ docs/formatstorage.html.in 15 Dec 2008 14:51:31 -0000
@@ -269,6 +269,13 @@
contains the MAC (eg SELinux) label string.
<span class="since">Since 0.4.1</span>
</dd>
+ <dt><code>backingstore</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 -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 15 Dec 2008 14:51:31 -0000
@@ -48,6 +48,19 @@
#include "xml.h"
+enum {
+ BACKING_STORE_OK,
+ BACKING_STORE_INVALID,
+ BACKING_STORE_ERROR,
+};
+
+static int cowGetBackingStore(virConnectPtr, char **, const unsigned char *,
+ size_t);
+static int qcowXGetBackingStore(virConnectPtr, char **, const unsigned char *,
+ size_t);
+static int vmdk4GetBackingStore(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 +77,220 @@
* -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 BACKING_STORE_* */
+ int (*getBackingStore)(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, cowGetBackingStore },
/* 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, qcowXGetBackingStore },
/* 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, qcowXGetBackingStore },
/* 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, vmdk4GetBackingStore },
/* 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
+cowGetBackingStore(virConnectPtr conn,
+ char **res,
+ const unsigned char *buf,
+ size_t buf_size)
+{
+ size_t len;
+
+ *res = NULL;
+ if (buf_size < 4+4+1024)
+ return BACKING_STORE_INVALID;
+ if (buf[4+4] == '\0') /* cow_header_v2.backing_file[0] */
+ return BACKING_STORE_OK;
+
+ len = 1024;
+ if (VIR_ALLOC_N(*res, len + 1) < 0) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY, _("backing store path"));
+ return BACKING_STORE_ERROR;
+ }
+ memcpy(*res, buf + 4+4, len); /* cow_header_v2.backing_file */
+ (*res)[len] = '\0';
+ if (VIR_REALLOC_N(*res, strlen(*res) + 1) < 0) {
+ /* Ignore failure */
+ }
+ return BACKING_STORE_OK;
+}
+
+static int
+qcowXGetBackingStore(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 BACKING_STORE_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]); /* QCowHeader.backing_file_offset */
+ if (offset > buf_size)
+ return BACKING_STORE_INVALID;
+ size = ((buf[4+4+8] << 24)
+ | (buf[4+4+8+1] << 16)
+ | (buf[4+4+8+2] << 8)
+ | buf[4+4+8+3]); /* QCowHeader.backing_file_size */
+ if (size == 0)
+ return BACKING_STORE_OK;
+ if (offset + size > buf_size || offset + size < offset)
+ return BACKING_STORE_INVALID;
+ if (size + 1 == 0)
+ return BACKING_STORE_INVALID;
+ if (VIR_ALLOC_N(*res, size + 1) < 0) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY, _("backing store path"));
+ return BACKING_STORE_ERROR;
+ }
+ memcpy(*res, buf + offset, size);
+ (*res)[size] = '\0';
+ return BACKING_STORE_OK;
+}
+
+static int
+vmdk4GetBackingStore(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 BACKING_STORE_INVALID;
+ 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 BACKING_STORE_OK;
+ start += strlen(prefix);
+ end = strchr(start, '"');
+ if (end == NULL)
+ return BACKING_STORE_INVALID;
+ if (end == start)
+ return BACKING_STORE_OK;
+ *end = '\0';
+ *res = strdup(start);
+ if (*res == NULL) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY, _("backing store path"));
+ return BACKING_STORE_ERROR;
+ }
+ return BACKING_STORE_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.
@@ -131,7 +298,7 @@
static int virStorageBackendProbeFile(virConnectPtr conn,
virStorageVolDefPtr def) {
int fd;
- unsigned char head[4096];
+ unsigned char head[20*512]; /* vmdk4GetBackingStore needs this much. */
int len, i, ret;
if ((fd = open(def->target.path, O_RDONLY)) < 0) {
@@ -219,6 +386,32 @@
/* Validation passed, we know the file format now */
def->target.format = fileTypeInfo[i].type;
+ if (fileTypeInfo[i].getBackingStore != NULL) {
+ char *base;
+
+ switch (fileTypeInfo[i].getBackingStore(conn, &base, head, len)) {
+ case BACKING_STORE_OK:
+ break;
+
+ case BACKING_STORE_INVALID:
+ continue;
+
+ case BACKING_STORE_ERROR:
+ return -1;
+ }
+ if (base == NULL)
+ def->target.backingStore = NULL;
+ else {
+ def->target.backingStore
+ = absolutePathFromBaseFile(def->target.path, base);
+ free(base);
+ if (def->target.backingStore == NULL) {
+ virStorageReportError(conn, VIR_ERR_NO_MEMORY,
+ _("backing store path"));
+ return -1;
+ }
+ }
+ }
return 0;
}
@@ -832,7 +1025,9 @@
#if HAVE_QEMU_IMG
const char *type;
char size[100];
- const char *imgargv[7];
+ const char *imgargv[9];
+ size_t i;
+ virStorageVolDefPtr backingStore;
if ((type = virStorageVolFormatFileSystemTypeToString(vol->target.format)) == NULL) {
virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
@@ -840,17 +1035,59 @@
vol->target.format);
return -1;
}
+ if (vol->target.backingStore == NULL)
+ backingStore = 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->getBackingStore == NULL) {
+ virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
+ _("copy-on-write not supported with "
+ "format %s"), type);
+ return -1;
+ }
+ backingStore = virStorageVolDefFindByKey(pool,
+ vol->target.backingStore);
+ if (backingStore == NULL) {
+ virStorageReportError(conn, VIR_ERR_NO_STORAGE_VOL,
+ _("unknown backing store volume key %s"),
+ vol->target.backingStore);
+ return -1;
+ }
+ if (access(backingStore->target.path, R_OK) != 0) {
+ virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
+ _("unaccessible backing store volume "
+ "with key %s: %s"),
+ vol->target.backingStore,
+ strerror(errno));
+ 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 (backingStore != NULL) {
+ imgargv[i++] = "-b";
+ imgargv[i++] = backingStore->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 @@
vol->target.format);
return -1;
}
+ if (vol->target.backingStore != 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);
Index: src/storage_conf.c
===================================================================
RCS file: /data/cvs/libvirt/src/storage_conf.c,v
retrieving revision 1.33
diff -u -r1.33 storage_conf.c
--- src/storage_conf.c 8 Dec 2008 11:28:37 -0000 1.33
+++ src/storage_conf.c 15 Dec 2008 14:51:31 -0000
@@ -247,6 +247,7 @@
VIR_FREE(def->target.path);
VIR_FREE(def->target.perms.label);
+ VIR_FREE(def->target.backingStore);
VIR_FREE(def);
}
@@ -993,6 +994,9 @@
if (virStorageVolDefParsePerms(conn, ctxt, &ret->target.perms) < 0)
goto cleanup;
+ ret->target.backingStore
+ = virXPathString(conn, "string(/volume/target/backingstore)", ctxt);
+
return ret;
cleanup:
@@ -1141,6 +1145,10 @@
def->target.perms.label);
virBufferAddLit(&buf," </permissions>\n");
+
+ if (def->target.backingStore)
+ virBufferVSprintf(&buf, " <backingstore>%s</backingstore>\n",
+ def->target.backingStore);
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 -r1.13 storage_conf.h
--- src/storage_conf.h 4 Dec 2008 22:00:14 -0000 1.13
+++ src/storage_conf.h 15 Dec 2008 14:51:31 -0000
@@ -73,6 +73,7 @@
char *path;
int format;
virStoragePerms perms;
+ char *backingStore;
};
--
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