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snapshot: fine-tune ability to start paused

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While it is nice that snapshots and saved images remember whether
the domain was running or paused, sometimes the restoration phase
wants to guarantee a particular state (paused to allow hot-plugging,
or running without needing to call resume).  This introduces new
flags to allow the control, and a later patch will implement the
flags for qemu.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_SAVE_RUNNING)
(VIR_DOMAIN_SAVE_PAUSED, VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING)
(VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED): New flags.
* src/libvirt.c (virDomainSaveFlags, virDomainRestoreFlags)
(virDomainManagedSave, virDomainSaveImageDefineXML)
(virDomainRevertToSnapshot): Document their use, and enforce
mutual exclusion.
This commit is contained in:
Eric Blake 2011-08-26 15:27:50 -06:00
parent c1ff5dc63d
commit 3cff66f487
2 changed files with 91 additions and 10 deletions
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12
include/libvirt/libvirt.h.in
View File

@ -960,11 +960,14 @@ int virDomainResume (virDomainPtr domain);
/**
* virDomainSaveRestoreFlags:
* Flags for use in virDomainSaveFlags(), virDomainManagedSave(), and
* virDomainRestoreFlags().
* Flags for use in virDomainSaveFlags(), virDomainManagedSave(),
* virDomainRestoreFlags(), and virDomainSaveImageDefineXML(). Not all
* flags apply to all these functions.
*/
typedef enum {
VIR_DOMAIN_SAVE_BYPASS_CACHE = 1 << 0, /* Avoid file system cache pollution */
VIR_DOMAIN_SAVE_RUNNING = 1 << 1, /* Favor running over paused */
VIR_DOMAIN_SAVE_PAUSED = 1 << 2, /* Favor paused over running */
} virDomainSaveRestoreFlags;
int virDomainSave (virDomainPtr domain,
@ -2579,6 +2582,11 @@ int virDomainHasCurrentSnapshot(virDomainPtr domain, unsigned int flags);
virDomainSnapshotPtr virDomainSnapshotCurrent(virDomainPtr domain,
unsigned int flags);
typedef enum {
VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING = 1 << 0, /* Run after revert */
VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED = 1 << 1, /* Pause after revert */
} virDomainSnapshotRevertFlags;
/* Revert the domain to a point-in-time snapshot. The
* state of the guest after this call will be the state
* of the guest when the snapshot in question was taken

89
src/libvirt.c
View File

@ -2310,7 +2310,7 @@ error:
*
* 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).
* listed as running anymore (this ends the life of a transient domain).
* Use virDomainRestore() to restore a domain after saving.
*
* See virDomainSaveFlags() for more control. Also, a save file can
@ -2379,7 +2379,7 @@ error:
*
* 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).
* listed as running anymore (this ends the life of a transient domain).
* Use virDomainRestore() to restore a domain after saving.
*
* If the hypervisor supports it, @dxml can be used to alter
@ -2394,6 +2394,12 @@ error:
* 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.
*
* Normally, the saved state file will remember whether the domain was
* running or paused, and restore defaults to the same state.
* Specifying VIR_DOMAIN_SAVE_RUNNING or VIR_DOMAIN_SAVE_PAUSED in
* @flags will override what state gets saved into the file. These
* two flags are mutually exclusive.
*
* A save file can be inspected or modified slightly with
* virDomainSaveImageGetXMLDesc() and virDomainSaveImageDefineXML().
*
@ -2425,6 +2431,12 @@ virDomainSaveFlags(virDomainPtr domain, const char *to,
goto error;
}
if ((flags & VIR_DOMAIN_SAVE_RUNNING) && (flags & VIR_DOMAIN_SAVE_PAUSED)) {
virLibDomainError(VIR_ERR_INVALID_ARG,
_("running and paused flags are mutually exclusive"));
goto error;
}
if (conn->driver->domainSaveFlags) {
int ret;
char *absolute_to;
@ -2532,6 +2544,12 @@ error:
* 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.
*
* Normally, the saved state file will remember whether the domain was
* running or paused, and restore defaults to the same state.
* Specifying VIR_DOMAIN_SAVE_RUNNING or VIR_DOMAIN_SAVE_PAUSED in
* @flags will override the default read from the file. These two
* flags are mutually exclusive.
*
* Returns 0 in case of success and -1 in case of failure.
*/
int
@ -2557,6 +2575,12 @@ virDomainRestoreFlags(virConnectPtr conn, const char *from, const char *dxml,
goto error;
}
if ((flags & VIR_DOMAIN_SAVE_RUNNING) && (flags & VIR_DOMAIN_SAVE_PAUSED)) {
virLibDomainError(VIR_ERR_INVALID_ARG,
_("running and paused flags are mutually exclusive"));
goto error;
}
if (conn->driver->domainRestoreFlags) {
int ret;
char *absolute_from;
@ -2661,7 +2685,7 @@ error:
* @conn: pointer to the hypervisor connection
* @file: path to saved state file
* @dxml: XML config for adjusting guest xml used on restore
* @flags: 0 for now
* @flags: bitwise-OR of virDomainSaveRestoreFlags
*
* This updates the definition of a domain stored in a saved state
* file. @file must be a file created previously by virDomainSave()
@ -2673,6 +2697,13 @@ error:
* disk device, to match renaming done as part of backing up the disk
* device while the domain is stopped.
*
* Normally, the saved state file will remember whether the domain was
* running or paused, and restore defaults to the same state.
* Specifying VIR_DOMAIN_SAVE_RUNNING or VIR_DOMAIN_SAVE_PAUSED in
* @flags will override the default saved into the file; omitting both
* leaves the file's default unchanged. These two flags are mutually
* exclusive.
*
* Returns 0 in case of success and -1 in case of failure.
*/
int
@ -2698,6 +2729,12 @@ virDomainSaveImageDefineXML(virConnectPtr conn, const char *file,
goto error;
}
if ((flags & VIR_DOMAIN_SAVE_RUNNING) && (flags & VIR_DOMAIN_SAVE_PAUSED)) {
virLibDomainError(VIR_ERR_INVALID_ARG,
_("running and paused flags are mutually exclusive"));
goto error;
}
if (conn->driver->domainSaveImageDefineXML) {
int ret;
char *absolute_file;
@ -7018,7 +7055,9 @@ error:
* @domain: pointer to a defined domain
*
* Launch a defined domain. If the call succeeds the domain moves from the
* defined to the running domains pools.
* defined to the running domains pools. The domain will be paused only
* if restoring from managed state created from a paused domain. For more
* control, see virDomainCreateWithFlags().
*
* Returns 0 in case of success, -1 in case of error
*/
@ -7064,9 +7103,12 @@ error:
* Launch a defined domain. If the call succeeds the domain moves from the
* defined to the running domains pools.
*
* If the VIR_DOMAIN_START_PAUSED flag is set, the guest domain
* will be started, but its CPUs will remain paused. The CPUs
* can later be manually started using virDomainResume.
* If the VIR_DOMAIN_START_PAUSED flag is set, or if the guest domain
* has a managed save image that requested paused state (see
* virDomainManagedSave()) the guest domain will be started, but its
* CPUs will remain paused. The CPUs can later be manually started
* using virDomainResume(). In all other cases, the guest domain will
* be running.
*
* If the VIR_DOMAIN_START_AUTODESTROY flag is set, the guest
* domain will be automatically destroyed when the virConnectPtr
@ -15391,6 +15433,12 @@ error:
* 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.
*
* Normally, the managed saved state will remember whether the domain
* was running or paused, and start will resume to the same state.
* Specifying VIR_DOMAIN_SAVE_RUNNING or VIR_DOMAIN_SAVE_PAUSED in
* @flags will override the default saved into the file. These two
* flags are mutually exclusive.
*
* Returns 0 in case of success or -1 in case of failure
*/
int virDomainManagedSave(virDomainPtr dom, unsigned int flags)
@ -15413,6 +15461,12 @@ int virDomainManagedSave(virDomainPtr dom, unsigned int flags)
goto error;
}
if ((flags & VIR_DOMAIN_SAVE_RUNNING) && (flags & VIR_DOMAIN_SAVE_PAUSED)) {
virLibDomainError(VIR_ERR_INVALID_ARG,
_("running and paused flags are mutually exclusive"));
goto error;
}
if (conn->driver->domainManagedSave) {
int ret;
@ -15844,10 +15898,22 @@ error:
/**
* virDomainRevertToSnapshot:
* @snapshot: a domain snapshot object
* @flags: unused flag parameters; callers should pass 0
* @flags: bitwise-OR of virDomainSnapshotRevertFlags
*
* Revert the domain to a given snapshot.
*
* Normally, the domain will revert to the same state the domain was
* in while the snapshot was taken (whether inactive, running, or
* paused), except that disk snapshots default to reverting to
* inactive state. Including VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING in
* @flags overrides the snapshot state to guarantee a running domain
* after the revert; or including VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED in
* @flags guarantees a paused domain after the revert. These two
* flags are mutually exclusive. While a persistent domain does not
* need either flag, it is not possible to revert a transient domain
* into an inactive state, so transient domains require the use of one
* of these two flags.
*
* Returns 0 if the creation is successful, -1 on error.
*/
int
@ -15873,6 +15939,13 @@ virDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
goto error;
}
if ((flags & VIR_DOMAIN_SNAPSHOT_REVERT_RUNNING) &&
(flags & VIR_DOMAIN_SNAPSHOT_REVERT_PAUSED)) {
virLibDomainError(VIR_ERR_INVALID_ARG,
_("running and paused flags are mutually exclusive"));
goto error;
}
if (conn->driver->domainRevertToSnapshot) {
int ret = conn->driver->domainRevertToSnapshot(snapshot, flags);
if (ret < 0)