[libvirt] [PATCHv2 05/16] save: document new public API
Eric Blake
eblake at redhat.com
Wed Jul 20 04:20:28 UTC 2011
In order to choose whether to use O_DIRECT when saving a domain image
to a file, we need a new flag. But virDomainSave was implemented
before our policy of all new APIs having a flag argument. Likewise
for virDomainRestore when restoring from a file.
The new flag name is chosen as CACHE_BYPASS so as not to preclude
a future solution that uses posix_fadvise once the Linux kernel has
a smarter implementation of that interface.
* include/libvirt/libvirt.h.in (virDomainCreateFlags)
(virDomainCoreDumpFlags): Add a flag.
(virDomainSaveFlags, virDomainRestoreFlags): New prototypes.
* src/libvirt.c (virDomainSaveFlags, virDomainRestoreFlags): New API.
* src/libvirt_public.syms: Export them.
* src/driver.h (virDrvDomainSaveFlags, virDrvDomainRestoreFlags):
New driver callbacks.
---
v2: rename flag from _DIRECT to _BYPASS_CACHE, and merged 1 and 11 of v1
include/libvirt/libvirt.h.in | 30 ++++++-
src/driver.h | 12 +++
src/libvirt.c | 181 +++++++++++++++++++++++++++++++++++++++++-
src/libvirt_public.syms | 2 +
4 files changed, 219 insertions(+), 6 deletions(-)
diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index 40ce0fc..20c5109 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -232,9 +232,10 @@ typedef virDomainInfo *virDomainInfoPtr;
* Domain.
*/
typedef enum {
- VIR_DOMAIN_NONE = 0, /* Default behavior */
- VIR_DOMAIN_START_PAUSED = 1 << 0, /* Launch guest in paused state */
- VIR_DOMAIN_START_AUTODESTROY = 1 << 1, /* Automatically kill guest when virConnectPtr is closed */
+ VIR_DOMAIN_NONE = 0, /* Default behavior */
+ VIR_DOMAIN_START_PAUSED = 1 << 0, /* Launch guest in paused state */
+ VIR_DOMAIN_START_AUTODESTROY = 1 << 1, /* Automatically kill guest when virConnectPtr is closed */
+ VIR_DOMAIN_START_BYPASS_CACHE = 1 << 2, /* Avoid file system cache pollution */
} virDomainCreateFlags;
@@ -657,8 +658,9 @@ typedef virDomainMemoryStatStruct *virDomainMemoryStatPtr;
/* Domain core dump flags. */
typedef enum {
- VIR_DUMP_CRASH = (1 << 0), /* crash after dump */
- VIR_DUMP_LIVE = (1 << 1), /* live dump */
+ VIR_DUMP_CRASH = (1 << 0), /* crash after dump */
+ VIR_DUMP_LIVE = (1 << 1), /* live dump */
+ VIR_DUMP_BYPASS_CACHE = (1 << 2), /* avoid file system cache pollution */
} virDomainCoreDumpFlags;
/* Domain migration flags. */
@@ -941,10 +943,28 @@ int virDomainResume (virDomainPtr domain);
/*
* Domain save/restore
*/
+
+/**
+ * virDomainSaveRestoreFlags:
+ * Flags for use in virDomainSaveFlags(), virDomainManagedSave(), and
+ * virDomainRestoreFlags().
+ */
+typedef enum {
+ VIR_DOMAIN_SAVE_BYPASS_CACHE = 1 << 0, /* Avoid file system cache pollution */
+} virDomainSaveRestoreFlags;
+
int virDomainSave (virDomainPtr domain,
const char *to);
+int virDomainSaveFlags (virDomainPtr domain,
+ const char *to,
+ const char *dxml,
+ unsigned int flags);
int virDomainRestore (virConnectPtr conn,
const char *from);
+int virDomainRestoreFlags (virConnectPtr conn,
+ const char *from,
+ const char *dxml,
+ unsigned int flags);
/*
* Managed domain save
diff --git a/src/driver.h b/src/driver.h
index 4c4955f..d931c9b 100644
--- a/src/driver.h
+++ b/src/driver.h
@@ -178,9 +178,19 @@ typedef int
(*virDrvDomainSave) (virDomainPtr domain,
const char *to);
typedef int
+ (*virDrvDomainSaveFlags) (virDomainPtr domain,
+ const char *to,
+ const char *dxml,
+ unsigned int flags);
+typedef int
(*virDrvDomainRestore) (virConnectPtr conn,
const char *from);
typedef int
+ (*virDrvDomainRestoreFlags) (virConnectPtr conn,
+ const char *from,
+ const char *dxml,
+ unsigned int flags);
+typedef int
(*virDrvDomainCoreDump) (virDomainPtr domain,
const char *to,
unsigned int flags);
@@ -714,7 +724,9 @@ struct _virDriver {
virDrvDomainGetState domainGetState;
virDrvDomainGetControlInfo domainGetControlInfo;
virDrvDomainSave domainSave;
+ virDrvDomainSaveFlags domainSaveFlags;
virDrvDomainRestore domainRestore;
+ virDrvDomainRestoreFlags domainRestoreFlags;
virDrvDomainCoreDump domainCoreDump;
virDrvDomainScreenshot domainScreenshot;
virDrvDomainSetVcpus domainSetVcpus;
diff --git a/src/libvirt.c b/src/libvirt.c
index 2f5241a..c769589 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -2242,6 +2242,8 @@ error:
* listed as running anymore (this may be a problem).
* Use virDomainRestore() to restore a domain after saving.
*
+ * See virDomainSaveFlags() for more control.
+ *
* Returns 0 in case of success and -1 in case of failure.
*/
int
@@ -2296,12 +2298,93 @@ error:
}
/**
+ * virDomainSaveFlags:
+ * @domain: a domain object
+ * @to: path for the output file
+ * @dxml: (optional) XML config for adjusting guest xml used on restore
+ * @flags: bitwise-OR of virDomainSaveRestoreFlags
+ *
+ * This method will suspend a domain and save its memory contents to
+ * a file on disk. After the call, if successful, the domain is not
+ * listed as running anymore (this may be a problem).
+ * Use virDomainRestore() to restore a domain after saving.
+ *
+ * If the hypervisor supports it, @dxml can be used to alter
+ * host-specific portions of the domain XML that will be used when
+ * restoring an image. For example, it is possible to alter the
+ * backing filename that is associated with a disk device, in order to
+ * prepare for file renaming done as part of backing up the disk
+ * device while the domain is stopped.
+ *
+ * If @flags includes VIR_DOMAIN_SAVE_BYPASS_CACHE, then libvirt will
+ * attempt to bypass the file system cache while creating the file, or
+ * fail if it cannot do so for the given system; this can allow less
+ * pressure on file system cache, but also risks slowing saves to NFS.
+ *
+ * Returns 0 in case of success and -1 in case of failure.
+ */
+int
+virDomainSaveFlags(virDomainPtr domain, const char *to,
+ const char *dxml, unsigned int flags)
+{
+ virConnectPtr conn;
+
+ VIR_DOMAIN_DEBUG(domain, "to=%s dxml=%s flags=%x",
+ to, NULLSTR(dxml), flags);
+
+ virResetLastError();
+
+ if (!VIR_IS_CONNECTED_DOMAIN(domain)) {
+ virLibDomainError(VIR_ERR_INVALID_DOMAIN, __FUNCTION__);
+ virDispatchError(NULL);
+ return -1;
+ }
+ if (domain->conn->flags & VIR_CONNECT_RO) {
+ virLibDomainError(VIR_ERR_OPERATION_DENIED, __FUNCTION__);
+ goto error;
+ }
+ conn = domain->conn;
+ if (to == NULL) {
+ virLibDomainError(VIR_ERR_INVALID_ARG, __FUNCTION__);
+ goto error;
+ }
+
+ if (conn->driver->domainSaveFlags) {
+ int ret;
+ char *absolute_to;
+
+ /* We must absolutize the file path as the save is done out of process */
+ if (virFileAbsPath(to, &absolute_to) < 0) {
+ virLibConnError(VIR_ERR_INTERNAL_ERROR,
+ _("could not build absolute output file path"));
+ goto error;
+ }
+
+ ret = conn->driver->domainSaveFlags(domain, absolute_to, dxml, flags);
+
+ VIR_FREE(absolute_to);
+
+ if (ret < 0)
+ goto error;
+ return ret;
+ }
+
+ virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
+
+error:
+ virDispatchError(domain->conn);
+ return -1;
+}
+
+/**
* virDomainRestore:
* @conn: pointer to the hypervisor connection
* @from: path to the input file
*
* This method will restore a domain saved to disk by virDomainSave().
*
+ * See virDomainRestoreFlags() for more control.
+ *
* Returns 0 in case of success and -1 in case of failure.
*/
int
@@ -2353,6 +2436,80 @@ error:
}
/**
+ * virDomainRestoreFlags:
+ * @conn: pointer to the hypervisor connection
+ * @from: path to the input file
+ * @dxml: (optional) XML config for adjusting guest xml used on restore
+ * @flags: bitwise-OR of virDomainSaveRestoreFlags
+ *
+ * This method will restore a domain saved to disk by virDomainSave().
+ *
+ * If the hypervisor supports it, @dxml can be used to alter
+ * host-specific portions of the domain XML that will be used when
+ * restoring an image. For example, it is possible to alter the
+ * backing filename that is associated with a disk device, in order to
+ * prepare for file renaming done as part of backing up the disk
+ * device while the domain is stopped.
+ *
+ * If @flags includes VIR_DOMAIN_SAVE_BYPASS_CACHE, then libvirt will
+ * attempt to bypass the file system cache while restoring the file, or
+ * fail if it cannot do so for the given system; this can allow less
+ * pressure on file system cache, but also risks slowing saves to NFS.
+ *
+ * Returns 0 in case of success and -1 in case of failure.
+ */
+int
+virDomainRestoreFlags(virConnectPtr conn, const char *from, const char *dxml,
+ unsigned int flags)
+{
+ VIR_DEBUG("conn=%p, from=%s, dxml=%s, flags=%x",
+ conn, from, NULLSTR(dxml), flags);
+
+ virResetLastError();
+
+ if (!VIR_IS_CONNECT(conn)) {
+ virLibConnError(VIR_ERR_INVALID_CONN, __FUNCTION__);
+ virDispatchError(NULL);
+ return -1;
+ }
+ if (conn->flags & VIR_CONNECT_RO) {
+ virLibConnError(VIR_ERR_OPERATION_DENIED, __FUNCTION__);
+ goto error;
+ }
+ if (from == NULL) {
+ virLibConnError(VIR_ERR_INVALID_ARG, __FUNCTION__);
+ goto error;
+ }
+
+ if (conn->driver->domainRestoreFlags) {
+ int ret;
+ char *absolute_from;
+
+ /* We must absolutize the file path as the restore is done out of process */
+ if (virFileAbsPath(from, &absolute_from) < 0) {
+ virLibConnError(VIR_ERR_INTERNAL_ERROR,
+ _("could not build absolute input file path"));
+ goto error;
+ }
+
+ ret = conn->driver->domainRestoreFlags(conn, absolute_from, dxml,
+ flags);
+
+ VIR_FREE(absolute_from);
+
+ if (ret < 0)
+ goto error;
+ return ret;
+ }
+
+ virLibConnError(VIR_ERR_NO_SUPPORT, __FUNCTION__);
+
+error:
+ virDispatchError(conn);
+ return -1;
+}
+
+/**
* virDomainCoreDump:
* @domain: a domain object
* @to: path for the core file
@@ -2362,6 +2519,17 @@ error:
* Note that for remote Xen Daemon the file path will be interpreted in
* the remote host.
*
+ * If @flags includes VIR_DUMP_CRASH, then leave the guest shut off with
+ * a crashed state after the dump completes. If @flags includes
+ * VIR_DUMP_LIVE, then make the core dump while continuing to allow
+ * the guest to run; otherwise, the guest is suspended during the dump.
+ * The above two flags are mutually exclusive.
+ *
+ * Additionally, if @flags includes VIR_DUMP_BYPASS_CACHE, then libvirt
+ * will attempt to bypass the file system cache while creating the file,
+ * or fail if it cannot do so for the given system; this can allow less
+ * pressure on file system cache, but also risks slowing saves to NFS.
+ *
* Returns 0 in case of success and -1 in case of failure.
*/
int
@@ -6612,6 +6780,12 @@ error:
* libvirtd daemon. Any domains marked for auto destroy will
* block attempts at migration or save-to-file
*
+ * If the VIR_DOMAIN_START_BYPASS_CACHE flag is set, and there is a
+ * managed save file for this domain (created by virDomainManagedSave()),
+ * then libvirt will attempt to bypass the file system cache while restoring
+ * the file, or fail if it cannot do so for the given system; this can allow
+ * less pressure on file system cache, but also risks slowing loads from NFS.
+ *
* Returns 0 in case of success, -1 in case of error
*/
int
@@ -14837,7 +15011,7 @@ error:
/**
* virDomainManagedSave:
* @dom: pointer to the domain
- * @flags: optional flags currently unused
+ * @flags: bitwise-OR of virDomainSaveRestoreFlags
*
* This method will suspend a domain and save its memory contents to
* a file on disk. After the call, if successful, the domain is not
@@ -14847,6 +15021,11 @@ error:
* restarted (automatically or via an explicit libvirt call).
* As a result any running domain is sure to not have a managed saved image.
*
+ * If @flags includes VIR_DOMAIN_SAVE_BYPASS_CACHE, then libvirt will
+ * attempt to bypass the file system cache while creating the file, or
+ * fail if it cannot do so for the given system; this can allow less
+ * pressure on file system cache, but also risks slowing saves to NFS.
+ *
* Returns 0 in case of success or -1 in case of failure
*/
int virDomainManagedSave(virDomainPtr dom, unsigned int flags)
diff --git a/src/libvirt_public.syms b/src/libvirt_public.syms
index 5cc480e..6935140 100644
--- a/src/libvirt_public.syms
+++ b/src/libvirt_public.syms
@@ -468,6 +468,8 @@ LIBVIRT_0.9.3 {
LIBVIRT_0.9.4 {
global:
+ virDomainRestoreFlags;
+ virDomainSaveFlags;
virDomainUndefineFlags;
} LIBVIRT_0.9.3;
--
1.7.4.4
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