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blockjob: implement shallow commit flag in qemu

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Now that we can crawl the chain of backing files, we can do
argument validation and implement the 'shallow' flag.  In
testing this, I discovered that it can be handy to pass the
shallow flag and an explicit base, as a means of validating
that the base is indeed the file we expected.

* src/qemu/qemu_driver.c (qemuDomainBlockCommit): Crawl through
chain to implement shallow flag.
* src/libvirt.c (virDomainBlockCommit): Relax API.
This commit is contained in:
Eric Blake 2012-10-13 07:12:31 -06:00
parent 2cbc1fd892
commit 0a220e2225
2 changed files with 51 additions and 14 deletions
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2
src/libvirt.c
View File

@ -19381,8 +19381,6 @@ int virDomainBlockCommit(virDomainPtr dom, const char *disk,
}
virCheckNonNullArgGoto(disk, error);
if (flags & VIR_DOMAIN_BLOCK_COMMIT_SHALLOW)
virCheckNullArgGoto(base, error);
if (conn->driver->domainBlockCommit) {
int ret;

63
src/qemu/qemu_driver.c
View File

@ -12665,8 +12665,12 @@ qemuDomainBlockCommit(virDomainPtr dom, const char *path, const char *base,
int ret = -1;
int idx;
virDomainDiskDefPtr disk;
const char *top_canon = NULL;
virStorageFileMetadataPtr top_meta = NULL;
const char *top_parent = NULL;
const char *base_canon = NULL;
virCheckFlags(0, -1);
virCheckFlags(VIR_DOMAIN_BLOCK_COMMIT_SHALLOW, -1);
if (!(vm = qemuDomObjFromDomain(dom)))
goto cleanup;
@ -12697,20 +12701,55 @@ qemuDomainBlockCommit(virDomainPtr dom, const char *path, const char *base,
disk->dst);
goto endjob;
}
if (qemuDomainDetermineDiskChain(driver, disk, false) < 0)
goto endjob;
if (!top)
top = disk->src;
if (!top) {
top_canon = disk->src;
top_meta = disk->backingChain;
} else if (!(top_canon = virStorageFileChainLookup(disk->backingChain,
disk->src,
top, &top_meta,
&top_parent))) {
virReportError(VIR_ERR_INVALID_ARG,
_("could not find top '%s' in chain for '%s'"),
top, path);
goto endjob;
}
if (!top_meta || !top_meta->backingStore) {
virReportError(VIR_ERR_INVALID_ARG,
_("top '%s' in chain for '%s' has no backing file"),
top, path);
goto endjob;
}
if (!base && (flags & VIR_DOMAIN_BLOCK_COMMIT_SHALLOW)) {
base_canon = top_meta->backingStore;
} else if (!(base_canon = virStorageFileChainLookup(top_meta, top_canon,
base, NULL, NULL))) {
virReportError(VIR_ERR_INVALID_ARG,
_("could not find base '%s' below '%s' in chain "
"for '%s'"),
base ? base : "(default)", top_canon, path);
goto endjob;
}
/* Note that this code exploits the fact that
* virStorageFileChainLookup guarantees a simple pointer
* comparison will work, rather than needing full-blown STREQ. */
if ((flags & VIR_DOMAIN_BLOCK_COMMIT_SHALLOW) &&
base_canon != top_meta->backingStore) {
virReportError(VIR_ERR_INVALID_ARG,
_("base '%s' is not immediately below '%s' in chain "
"for '%s'"),
base, top_canon, path);
goto endjob;
}
/* XXX For now, we are relying on qemu to check that 'top' and
* 'base' resolve to members of the backing chain in correct
* order; but if we ever get more paranoid and track the backing
* chain ourself, we should be pre-validating the data rather than
* relying on qemu. For that matter, we need to be changing the
* SELinux label on both 'base' and the parent of 'top', so that
* qemu can open(O_RDWR) those files for the duration of the
* commit. */
/* XXX We need to be changing the SELinux label on both 'base' and
* the parent of 'top', so that qemu can open(O_RDWR) those files
* for the duration of the commit. */
qemuDomainObjEnterMonitor(driver, vm);
ret = qemuMonitorBlockCommit(priv->mon, device, top, base, bandwidth);
ret = qemuMonitorBlockCommit(priv->mon, device, top_canon, base_canon,
bandwidth);
qemuDomainObjExitMonitor(driver, vm);
endjob: