July 2011 - Devel - libvirt List Archives

[libvirt] RFC: API additions for enhanced snapshot support
by Eric Blake 28 Jul '11

28 Jul '11

Right now, libvirt has a snapshot API via virDomainSnapshotCreateXML, but for qemu domains, it only works if all the guest disk images are qcow2, and qemu rather than libvirt does all the work. However, it has a couple of drawbacks: it is inherently tied to domains (there is no way to manage snapshots of storage volumes not tied to a domain, even though libvirt does that for qcow2 images associated with offline qemu domains by using the qemu-img application). And it necessarily operates on all of the images associated with a domain in parallel - if any disk image is not qcow2, the snapshot fails, and there is no way to select a subset of disks to save. However, it works on both active (disk and memory state) and inactive domains (just disk state). Upstream qemu is developing a 'live snapshot' feature, which allows the creation of a snapshot without the current downtime of several seconds required by the current 'savevm' monitor command, as well as means for controlling applications (libvirt) to request that qemu pause I/O to a particular disk, then externally perform a snapshot, then tell qemu to resume I/O (perhaps on a different file name or fd from the host, but with no change to the contents seen by the guest). Eventually, these changes will make it possible for libvirt to create fast snapshots of LVM partitions or btrfs files for guest disk images, as well as to select which disks are saved in a snapshot (that is, save a crash-consistent state of a subset of disks, without the corresponding RAM state, rather than making a full system restore point); the latter would work best with guest cooperation to quiesce disks before qemu pauses I/O to that disk, but that is an orthogonal enhancement. However, my first goal with API enhancements is to merely prove that libvirt can manage a live snapshot by using qemu-img on a qcow2 image rather than the current 'savevm' approach of qemu doing all the work. Additionally, libvirt provides the virDomainSave command, which saves just the state of the domain's memory, and stops the guest. A crude libvirt-only snapshot could thus already be done by using virDomainSave, then externally doing a snapshot of all disk images associated with the domain by using virStorageVol APIs, except that such APIs don't yet exist. Additionally, virDomainSave has no flags argument, so there is no way to request that the guest be resumed after the snapshot completes. Right now, I'm proposing the addition of virDomainSaveFlags, along with a series of virStorageVolSnapshot* APIs that mirror the virDomainSnapshot* APIs. This would mean adding: /* Opaque type to manage a snapshot of a single storage volume. */ typedef virStorageVolSnapshotPtr; /* Create a snapshot of a storage volume. XML is optional, if non-NULL, it would be a new top-level element <volsnapshot> which is similar to the top-level <domainsnapshot> for virDomainSnapshotCreateXML, to specify name and description. Flags is 0 for now. */ virStorageVolSnapshotPtr virDomainSnapshotCreateXML(virStorageVolPtr vol, const char *xml, unsigned int flags); [For qcow2, this would be implemented with 'qemu-img snapshot -c', similar to what virDomainSnapshotXML already does on inactive domains. Later, we can add LVM and btrfs support, or even allow full file copies of any file type. Also in the future, we could enhance XML to take a new element that describes a relationship between the name of the original and of the snapshot, in the case where a new filename has to be created to complete the snapshot process.] /* Probe if vol has snapshots. 1 if true, 0 if false, -1 on error. Flags is 0 for now. */ int virStorageVolHasCurrentSnapshot(virStorageVolPtr vol, unsigned int flags); [For qcow2 images, snapshots can be contained within the same file and managed with qemu-img -l, but for other formats, this may mean that libvirt has to start managing externally saved data associated with the storage pool that associates snapshots with filenames. In fact, even for qcow2 it might be useful to support creation of new files backed by the previous snapshot rather than cramming multiple snapshots in one file, so we may have a use for flags to filter out the presence of single-file vs. multiple-file snapshot setups.] /* Revert a volume back to the state of a snapshot, returning 0 on success. Flags is 0 for now. */ int virStorageVolRevertToSnapsot(virStorageVolSnapshotPtr snapshot, unsigned int flags); [For qcow2, this would involve qemu-img snapshot -a. Here, a useful flag might be whether to delete any changes made after the point of the snapshot; virDomainRevertToSnapshot should probably honor the same type of flag.] /* Return the most recent snapshot of a volume, if one exists, or NULL on failure. Flags is 0 for now. */ virStorageVolSnapshotPtr virStorageVolSnapshotCurrent(virStorageVolPtr vol, unsigned int flags); /* Delete the storage associated with a snapshot (although the opaque snapshot object must still be independently freed). If flags is 0, any child snapshots based off of this one are rebased onto the parent; if flags is VIR_STORAGE_VOL_SNAPSHOT_DELETE_CHILDREN , then any child snapshots based off of this one are also deleted. */ int virStorageVolSnapshotDelete(virStorageVolSnapshotPtr snapshot, unsigned int flags); [For qcow2, this would involve qemu-img snapshot -d. For multiple-file snapshots, this would also involve qemu-img commit.] /* Free the object returned by virStorageVolSnapshot{Current,CreateXML,LookupByName}. The storage snapshot associated with this object still exists, if it has not been deleted by virStorageVolSnapshotDelete. */ int virStorageVolSnapshotFree(virStorageVolSnapshotPtr snapshot); /* Return the <volsnapshot> XML details about this snapshot object. Flags is 0 for now. */ int virStorageVolSnapshotGetXMLDesc(virStorageVolSnapshotPtr snapshot, unsigned int flags); /* Return the names of all snapshots associated with this volume, using len from virStorageVolSnapshotLen. Flags is 0 for now. */ int virStorageVolSnapshotListNames(virStorageVolPtr vol, char **names, int nameslen, unsigned int flags); [For qcow2, this involves qemu-img -l. Additionally, if virStorageVolHasCurrentSnapshot learns to filter on in-file vs. multi-file snapshots, then the same flags would apply here.] /* Get the opaque object tied to a snapshot name. Flags is 0 for now. */ virStorageVolSnapshotPtr virStorageVolSnapshotLookupByName(virStorageVolPtr vol, const char *name, unsigned int flags); /* Determine how many snapshots are tied to a volume, or -1 on error. Flags is 0 for now. */ int virStorageVolSnapshotNum(virStorageVolPtr vol, unsigned int flags); [Same flags as for virStorageVolSnapshotListNames.] /* Save a domain into the file 'to' with additional actions. If flags is 0, then xml is ignored, and this is like virDomainSave. If flags includes VIR_DOMAIN_SAVE_DISKS, then all of the associated disk images are also snapshotted, as if by virStorageVolSnapshotCreateXML; the xml argument is optional, but if present, it should be a <domainsnapshot> element with <disk> sub-elements for directions on each disk that needs a non-empty xml argument for proper volume snapshot creation. If flags includes VIR_DOMAIN_SAVE_RESUME, then the guest is resumed after the offline snapshot is complete (note that VIR_DOMAIN_SAVE_RESUME without VIR_DOMAIN_SAVE_DISKS makes little sense, as a saved state file is rendered useless if the disk images are modified before it is resumed). If flags includes VIR_DOMAIN_SAVE_QUIESCE, this requests that a guest agent quiesce disk state before the saved state file is created. */ int virDomainSaveFlags(virDomainPtr domain, const char *to, const char *xml, unsigned int flags); Also, the existing virDomainSnapshotCreateXML can be made more powerful by adding new flags and enhancing the existing XML for <domainsnapshot>. When flags is 0, the current behavior of saving memory state alongside all disks (for running domains, via savevm) or just snapshotting all disks with default settings (for offline domains, via qemu-img) is kept. If flags includes VIR_DOMAIN_SNAPSHOT_LIVE, then the guest must be running, and the new monitor commands for live snapshots are used. If flags includes VIR_DOMAIN_SNAPSHOT_DISKS_ONLY, then only the disks are snapshotted (on a running guest, this generally means they will only be crash-consistent, and will need an fsck before that disk state can be remounted), but it will shave off time by not saving memory. If flags includes VIR_DOMAIN_SNAPSHOT_QUIESCE, then this will additionally request that a guest agent quiesce disk state before the live snapshot is taken (increasing the likelihood of a stable disk, rather than a crash-consistent disk; but it requires cooperation from the guest so it is no more reliable than memballoon changes). As for the XML changes, it makes sense to snapshot just a subset of disks when you only care about crash-consistent state or if you can rely on a guest agent to quiesce the subset of disk(s) you care about, so the existing <domainsnapshot> element needs a new optional subelement to control which disks are snapshotted; additionally, this subelement will be useful for disk image formats that require additional complexity (such as a secondary file name, rather than the inline snapshot feature of qcow2). I'm envisioning something like the following: <domainsnapshot> <name>whatever</name> <disk name='/path/to/image1' snapshot='no'/> <disk name='/path/to/image2'> <volsnapshot>...</volsnapshot> </disk> </domainsnapshot> where there can be up to as many <disk> elements as there are disk <devices> in the domain xml; any domain disk not listed is given default treatment. The name attribute of <disk> is mandatory, in order to match this disk element to one of the domain disks. The snapshot='yes|no' attribute is optional, defaulting to yes, in order to skip a particular disk. The <volsnapshot> subelement is optional, but if present, it would be the same XML as is provided to the virStorageVolSnapshotCreateXML. [And since my first phase of implementation will be focused on inline qcow2 snapshots, I don't yet know what that XML will need to contain for any other type of snapshots, such as mapping out how the snapshot backing file will be named in relation to the possibly new live file.] Any feedback on this approach? Any other APIs that would be useful to add? I'd like to get all the new APIs in place for 0.9.3 with minimal qcow2 functionality, then use the time before 0.9.4 to further enhance the APIs to cover more snapshot cases but without having to add any new APIs. -- Eric Blake eblake(a)redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org

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[libvirt] [PATCH] virsh: avoid missing zero value judgement in cmdBlkiotune
by ajia＠redhat.com 28 Jul '11

28 Jul '11

* tools/virsh.c: avoid missing zero value judgement in cmdBlkiotune, when weight is equal to 0, the cmdBlkiotune will not raise any error information when judge weight value first time, and execute else branch to judge weight value again, strncpy(temp->field, VIR_DOMAIN_BLKIO_WEIGHT, sizeof(temp->field)) will be not executed for ever. However, if and only if param->field is equal to VIR_DOMAIN_BLKIO_WEIGHT, underlying qemuDomainSetBlkioParameters function will check whether weight value is in range [100, 1000]. * how to reproduce? % virsh blkiotune ${guestname} --weight 0 Signed-off-by: Alex Jia <ajia(a)redhat.com> --- tools/virsh.c | 10 ++++------ 1 files changed, 4 insertions(+), 6 deletions(-) diff --git a/tools/virsh.c b/tools/virsh.c index 8bd22dc..183d7c6 100644 --- a/tools/virsh.c +++ b/tools/virsh.c @@ -4037,12 +4037,10 @@ cmdBlkiotune(vshControl * ctl, const vshCmd * cmd) goto cleanup; } - if (weight) { - nparams++; - if (weight < 0) { - vshError(ctl, _("Invalid value of %d for I/O weight"), weight); - goto cleanup; - } + nparams++; + if (weight <= 0) { + vshError(ctl, _("Invalid value of %d for I/O weight"), weight); + goto cleanup; } if (nparams == 0) { -- 1.7.1

1 0

[libvirt] [PATCH 1/4] python: add python binding for virDomainGetBlkioParameters
by Hu Tao 28 Jul '11

28 Jul '11

--- python/libvirt-override-api.xml | 6 +- python/libvirt-override.c | 79 +++++++++++++++++++++++++++++++++++++- 2 files changed, 79 insertions(+), 6 deletions(-) diff --git a/python/libvirt-override-api.xml b/python/libvirt-override-api.xml index a8929b1..00f8e6a 100644 --- a/python/libvirt-override-api.xml +++ b/python/libvirt-override-api.xml @@ -208,10 +208,10 @@ <arg name='params' type='virBlkioParameterPtr' info='pointer to blkio tunable objects'/> </function> <function name='virDomainGetBlkioParameters' file='python'> - <info>Get the blkio parameters, the @params array will be filled with the values.</info> - <return type='int' info='-1 in case of error, 0 in case of success.'/> + <info>Get the blkio parameters</info> + <return type='virSchedParameterPtr' info='None in case of error, returns a dictionary of params'/> <arg name='domain' type='virDomainPtr' info='pointer to domain object'/> - <arg name='params' type='virBlkioParameterPtr' info='pointer to blkio tunable objects'/> + <arg name='flags' type='int' info='an OR'ed set of virDomainModificationImpact'/> </function> <function name='virDomainSetMemoryParameters' file='python'> <info>Change the memory tunables</info> diff --git a/python/libvirt-override.c b/python/libvirt-override.c index 70e0238..beb0969 100644 --- a/python/libvirt-override.c +++ b/python/libvirt-override.c @@ -572,11 +572,84 @@ libvirt_virDomainSetBlkioParameters(PyObject *self ATTRIBUTE_UNUSED, return VIR_PY_INT_FAIL; } -/* FIXME: This is a place holder for the implementation. */ static PyObject * libvirt_virDomainGetBlkioParameters(PyObject *self ATTRIBUTE_UNUSED, - PyObject *args ATTRIBUTE_UNUSED) { - return VIR_PY_INT_FAIL; + PyObject *args) { + virDomainPtr domain; + PyObject *pyobj_domain, *info; + int i_retval; + int nparams = 0, i; + unsigned int flags; + virTypedParameterPtr params; + + if (!PyArg_ParseTuple(args, (char *)"Oi:virDomainGetBlkioParameters", + &pyobj_domain, &flags)) + return(NULL); + domain = (virDomainPtr) PyvirDomain_Get(pyobj_domain); + + LIBVIRT_BEGIN_ALLOW_THREADS; + i_retval = virDomainGetBlkioParameters(domain, NULL, &nparams, flags); + LIBVIRT_END_ALLOW_THREADS; + + if (i_retval < 0) + return VIR_PY_NONE; + + if ((params = malloc(sizeof(*params)*nparams)) == NULL) + return VIR_PY_NONE; + + LIBVIRT_BEGIN_ALLOW_THREADS; + i_retval = virDomainGetBlkioParameters(domain, params, &nparams, flags); + LIBVIRT_END_ALLOW_THREADS; + + if (i_retval < 0) { + free(params); + return VIR_PY_NONE; + } + + /* convert to a Python tuple of long objects */ + if ((info = PyDict_New()) == NULL) { + free(params); + return VIR_PY_NONE; + } + for (i = 0 ; i < nparams ; i++) { + PyObject *key, *val; + + switch (params[i].type) { + case VIR_TYPED_PARAM_INT: + val = PyInt_FromLong((long)params[i].value.i); + break; + + case VIR_TYPED_PARAM_UINT: + val = PyInt_FromLong((long)params[i].value.ui); + break; + + case VIR_TYPED_PARAM_LLONG: + val = PyLong_FromLongLong((long long)params[i].value.l); + break; + + case VIR_TYPED_PARAM_ULLONG: + val = PyLong_FromLongLong((long long)params[i].value.ul); + break; + + case VIR_TYPED_PARAM_DOUBLE: + val = PyFloat_FromDouble((double)params[i].value.d); + break; + + case VIR_TYPED_PARAM_BOOLEAN: + val = PyBool_FromLong((long)params[i].value.b); + break; + + default: + free(params); + Py_DECREF(info); + return VIR_PY_NONE; + } + + key = libvirt_constcharPtrWrap(params[i].field); + PyDict_SetItem(info, key, val); + } + free(params); + return(info); } /* FIXME: This is a place holder for the implementation. */ -- 1.7.3.1

2 8

[libvirt] [PATCH 00/19] Rollback migration when libvirtd restarts
by Jiri Denemark 28 Jul '11

28 Jul '11

This series is also available at https://gitorious.org/~jirka/libvirt/jirka-staging/commits/migration-recove… The series does several things: - persists current job and its phase in status xml - allows safe monitor commands to be run during migration/save/dump jobs - implements recovery when libvirtd is restarted while a job is active - consolidates some code and fixes bugs I found when working in the area The series is not perfect and still needs some corner cases to be fixed but I think it's better to send the series for review now and add small additional fixes in the next version(s) instead of waiting for it to be perfect. Jiri Denemark (19): qemu: Separate job related data into a new object qemu: Consolidate BeginJob{,WithDriver} into a single method qemu: Consolidate {Enter,Exit}Monitor{,WithDriver} qemu: Allow all query commands to be run during long jobs qemu: Save job type in domain status XML qemu: Recover from interrupted jobs qemu: Add support for job phase qemu: Consolidate qemuMigrationPrepare{Direct,Tunnel} qemu: Implement migration job phases qemu: Migration job on destination daemon qemu: Migration job on source daemon qemu: Recover from interrupted migration qemu: Fix monitor unlocking in some error paths qemu: Remove special case for virDomainGetBlockInfo qemu: Remove special case for virDomainBlockStats qemu: Remove special case for virDomainMigrateSetMaxSpeed qemu: Remove special case for virDomainMigrateSetMaxDowntime qemu: Remove special case for virDomainSuspend qemu: Remove special case for virDomainAbortJob src/libvirt.c | 11 +- src/qemu/MIGRATION.txt | 55 +++ src/qemu/qemu_domain.c | 575 ++++++++++++++++++++++++------- src/qemu/qemu_domain.h | 130 +++++-- src/qemu/qemu_driver.c | 467 +++++++++++++------------ src/qemu/qemu_hotplug.c | 50 ++-- src/qemu/qemu_migration.c | 849 +++++++++++++++++++++++---------------------- src/qemu/qemu_migration.h | 36 ++ src/qemu/qemu_process.c | 244 ++++++++++++- 9 files changed, 1569 insertions(+), 848 deletions(-) create mode 100644 src/qemu/MIGRATION.txt -- 1.7.6

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[libvirt] [PATCH] virsh: fix memory leak in cmdVolPath code
by ajia＠redhat.com 28 Jul '11

28 Jul '11

* tools/virsh.c: avoid memory leak in cmdVolPath. * how to reproduce? % dd if=/dev/zero of=/var/lib/libvirt/images/foo.img count=1 bs=10M % virsh pool-refresh default % valgrind -v --leak-check=full virsh vol-path --vol /var/lib/libvirt/images/foo.img * actual results: Detected in valgrind run: ==16436== 32 bytes in 1 blocks are definitely lost in loss record 7 of 22 ==16436== at 0x4A05FDE: malloc (vg_replace_malloc.c:236) ==16436== by 0x386A314B3D: xdr_string (in /lib64/libc-2.12.so) ==16436== by 0x3DF8CD770D: xdr_remote_nonnull_string (remote_protocol.c:30) ==16436== by 0x3DF8CD7EC8: xdr_remote_storage_vol_get_path_ret (remote_protocol.c:2952) ==16436== by 0x3DF8CDF161: virNetMessageDecodePayload (virnetmessage.c:286) ==16436== by 0x3DF8CDE9E5: virNetClientProgramCall (virnetclientprogram.c:318) ==16436== by 0x3DF8CC28A2: call (remote_driver.c:3929) ==16436== by 0x3DF8CC8412: remoteStorageVolGetPath (remote_client_bodies.h:5219) ==16436== by 0x3DF8C9BF14: virStorageVolGetPath (libvirt.c:11389) ==16436== by 0x418ECA: cmdVolPath (virsh.c:8754) ==16436== by 0x410CC2: vshCommandRun (virsh.c:12758) ==16436== by 0x41F286: main (virsh.c:14110) ==16436== ==16436== LEAK SUMMARY: ==16436== definitely lost: 32 bytes in 1 blocks Signed-off-by: Alex Jia <ajia(a)redhat.com> --- tools/virsh.c | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/tools/virsh.c b/tools/virsh.c index 841df61..d194a8b 100644 --- a/tools/virsh.c +++ b/tools/virsh.c @@ -9326,6 +9326,7 @@ cmdVolPath(vshControl *ctl, const vshCmd *cmd) { virStorageVolPtr vol; const char *name = NULL; + char * StorageVolPath; if (!vshConnectionUsability(ctl, ctl->conn)) return false; @@ -9334,7 +9335,13 @@ cmdVolPath(vshControl *ctl, const vshCmd *cmd) return false; } - vshPrint(ctl, "%s\n", virStorageVolGetPath(vol)); + if ((StorageVolPath = virStorageVolGetPath(vol)) == NULL) { + virStorageVolFree(vol); + return false; + } + + vshPrint(ctl, "%s\n", StorageVolPath); + VIR_FREE(StorageVolPath); virStorageVolFree(vol); return true; } -- 1.7.1

3 3

[libvirt] Memory leak of the remoteDomainSet* functions
by Osier Yang 28 Jul '11

28 Jul '11

Hello, there Per bug https://bugzilla.redhat.com/show_bug.cgi?id=725322, should we change the remoteDomainSet* functions into "skipgen", and fix the leaks like below? (NB, new VIR_FREE statements) static int remoteDomainSetBlkioParameters(virDomainPtr dom, virTypedParameterPtr params, int nparams, unsigned int flags) { int rv = -1; int i; struct private_data *priv = dom->conn->privateData; remote_domain_set_blkio_parameters_args args; remote_domain_set_blkio_parameters_args args; remoteDriverLock(priv); make_nonnull_domain(&args.dom, dom); args.flags = flags; if (remoteSerializeTypedParameters(params, nparams, &args.params.params_val, &args.params.params_len) < 0) { for (i = 0; i < nparams; i++) { VIR_FREE(args.params.params_val[i].field); } VIR_FREE(args.params.params_val); xdr_free((xdrproc_t)xdr_remote_domain_set_blkio_parameters_args, (char *)&args); goto done; } if (call(dom->conn, priv, 0, REMOTE_PROC_DOMAIN_SET_BLKIO_PARAMETERS, (xdrproc_t)xdr_remote_domain_set_blkio_parameters_args, (char *)&args, (xdrproc_t)xdr_void, (char *)NULL) == -1) { goto done; } rv = 0; done: if (args.params.params_val) { for (i = 0; i < nparams; i++) { VIR_FREE(args.params.params_val[i].field); } VIR_FREE(args.params.params_val); } remoteDriverUnlock(priv); return rv; } Regards, Osier

2 3

[libvirt] [PATCH] qemu: Remove bogus codes in function getCompressionType
by Osier Yang 28 Jul '11

28 Jul '11

The error will never be reported, remove the codes, and also improve the docs in qemu.conf to tell user the truth. --- src/qemu/qemu.conf | 4 ++++ src/qemu/qemu_driver.c | 16 +++++----------- 2 files changed, 9 insertions(+), 11 deletions(-) diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf index 145062c..75d945b 100644 --- a/src/qemu/qemu.conf +++ b/src/qemu/qemu.conf @@ -199,6 +199,10 @@ # save_image_format is used when you use 'virsh save' at scheduled saving. # dump_image_format is used when you use 'virsh dump' at emergency crashdump. # +# If the specified format is not valid (the valid formats are "raw", "lzop", +# "gzip", "bzip2", and "xz"), or the compress program is not available, "raw" +# will be used as the format silently without error or warning. +# # save_image_format = "raw" # dump_image_format = "raw" diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index b928004..48fc46a 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -2712,19 +2712,13 @@ getCompressionType(struct qemud_driver *driver) */ if (driver->dumpImageFormat) { compress = qemudSaveCompressionTypeFromString(driver->dumpImageFormat); - if (compress < 0) { - qemuReportError(VIR_ERR_OPERATION_FAILED, "%s", - _("Invalid dump image format specified in " - "configuration file, using raw")); + /* Use "raw" as the format if the specified format is not valid, + * or the compress program is not available, + */ + if (compress < 0) return QEMUD_SAVE_FORMAT_RAW; - } - if (!qemudCompressProgramAvailable(compress)) { - qemuReportError(VIR_ERR_OPERATION_FAILED, - "%s", _("Compression program for dump image format " - "in configuration file isn't available, " - "using raw")); + if (!qemudCompressProgramAvailable(compress)) return QEMUD_SAVE_FORMAT_RAW; - } } return compress; } -- 1.7.6

2 4

[libvirt] [PATCH] qemu: improve thread documentation
by Eric Blake 27 Jul '11

27 Jul '11

* src/qemu/THREADS.txt: Fix problems with typos, grammar, and outdated examples. --- Doc only, so pushing under the trivial rule. src/qemu/THREADS.txt | 30 ++++++++++++++++-------------- 1 files changed, 16 insertions(+), 14 deletions(-) diff --git a/src/qemu/THREADS.txt b/src/qemu/THREADS.txt index 3a27a85..e73076c 100644 --- a/src/qemu/THREADS.txt +++ b/src/qemu/THREADS.txt @@ -6,7 +6,7 @@ the QEMU driver. The criteria for this model are: - Objects must never be exclusively locked for any prolonged time - Code which sleeps must be able to time out after suitable period - - Must be safe against dispatch asynchronous events from monitor + - Must be safe against dispatch of asynchronous events from monitor Basic locking primitives @@ -19,7 +19,7 @@ There are a number of locks on various objects This is the top level lock on the entire driver. Every API call in the QEMU driver is blocked while this is held, though some internal callbacks may still run asynchronously. This lock must never be held - for anything which sleeps/waits (ie monitor commands) + for anything which sleeps/waits (i.e. monitor commands) When obtaining the driver lock, under *NO* circumstances must any lock be held on a virDomainObjPtr. This *WILL* result in @@ -44,7 +44,7 @@ There are a number of locks on various objects to have the driver locked when re-acquiring the dropped locked, since the reference count prevents it being freed by another thread. - This lock must not be held for anything which sleeps/waits (ie monitor + This lock must not be held for anything which sleeps/waits (i.e. monitor commands). @@ -80,7 +80,7 @@ There are a number of locks on various objects whenever it hits a piece of code which may sleep/wait, and re-acquire it after the sleep/wait. Whenever an asynchronous job wants to talk to the monitor, it needs to acquire nested job (a - special kind of normla job) to obtain exclusive access to the + special kind of normal job) to obtain exclusive access to the monitor. Since the virDomainObjPtr lock was dropped while waiting for the @@ -139,7 +139,7 @@ To acquire the normal job condition - Increments ref count on virDomainObjPtr - Waits until the job is compatible with current async job or no async job is running - - Waits job.cond condition 'job.active != 0' using virDomainObjPtr + - Waits for job.cond condition 'job.active != 0' using virDomainObjPtr mutex - Rechecks if the job is still compatible and repeats waiting if it isn't @@ -150,7 +150,7 @@ To acquire the normal job condition - Unlocks driver - Waits until the job is compatible with current async job or no async job is running - - Waits job.cond condition 'job.active != 0' using virDomainObjPtr + - Waits for job.cond condition 'job.active != 0' using virDomainObjPtr mutex - Rechecks if the job is still compatible and repeats waiting if it isn't @@ -160,7 +160,7 @@ To acquire the normal job condition - Locks virDomainObjPtr NB: this variant is required in order to comply with lock ordering - rules for virDomainObjPtr vs driver + rules for virDomainObjPtr vs. driver qemuDomainObjEndJob() @@ -175,7 +175,7 @@ To acquire the asynchronous job condition qemuDomainObjBeginAsyncJob() (if driver is unlocked) - Increments ref count on virDomainObjPtr - Waits until no async job is running - - Waits job.cond condition 'job.active != 0' using virDomainObjPtr + - Waits for job.cond condition 'job.active != 0' using virDomainObjPtr mutex - Rechecks if any async job was started while waiting on job.cond and repeats waiting in that case @@ -185,7 +185,7 @@ To acquire the asynchronous job condition - Increments ref count on virDomainObjPtr - Unlocks driver - Waits until no async job is running - - Waits job.cond condition 'job.active != 0' using virDomainObjPtr + - Waits for job.cond condition 'job.active != 0' using virDomainObjPtr mutex - Rechecks if any async job was started while waiting on job.cond and repeats waiting in that case @@ -271,7 +271,7 @@ Design patterns - * Accessing something directly todo with a virDomainObjPtr + * Accessing something directly to do with a virDomainObjPtr virDomainObjPtr obj; @@ -285,7 +285,7 @@ Design patterns - * Accessing something directly todo with a virDomainObjPtr and driver + * Accessing something directly to do with a virDomainObjPtr and driver virDomainObjPtr obj; @@ -299,11 +299,11 @@ Design patterns - * Updating something directly todo with a virDomainObjPtr + * Updating something directly to do with a virDomainObjPtr virDomainObjPtr obj; - qemuDriverLockRO(driver); + qemuDriverLock(driver); obj = virDomainFindByUUID(driver->domains, dom->uuid); qemuDriverUnlock(driver); @@ -324,7 +324,7 @@ Design patterns virDomainObjPtr obj; qemuDomainObjPrivatePtr priv; - qemuDriverLockRO(driver); + qemuDriverLock(driver); obj = virDomainFindByUUID(driver->domains, dom->uuid); qemuDriverUnlock(driver); @@ -333,6 +333,7 @@ Design patterns ...do prep work... if (virDomainObjIsActive(vm)) { + /* using ignore_value is safe since vm is active */ ignore_value(qemuDomainObjEnterMonitor(obj)); qemuMonitorXXXX(priv->mon); qemuDomainObjExitMonitor(obj); @@ -360,6 +361,7 @@ Design patterns ...do prep work... if (virDomainObjIsActive(vm)) { + /* using ignore_value is safe since vm is active */ ignore_value(qemuDomainObjEnterMonitorWithDriver(driver, obj)); qemuMonitorXXXX(priv->mon); qemuDomainObjExitMonitorWithDriver(driver, obj); -- 1.7.4.4

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[libvirt] [PATCH] virsh: expose change-protection during migration
by Eric Blake 27 Jul '11

27 Jul '11

* tools/virsh.c (doMigrate): Add --change-protection flag. * tools/virsh.pod (migrate): Document it. --- As promised here: https://www.redhat.com/archives/libvir-list/2011-July/msg01919.html tools/virsh.c | 4 ++++ tools/virsh.pod | 9 +++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/tools/virsh.c b/tools/virsh.c index 113124f..34036f9 100644 --- a/tools/virsh.c +++ b/tools/virsh.c @@ -4830,6 +4830,8 @@ static const vshCmdOptDef opts_migrate[] = { {"suspend", VSH_OT_BOOL, 0, N_("do not restart the domain on the destination host")}, {"copy-storage-all", VSH_OT_BOOL, 0, N_("migration with non-shared storage with full disk copy")}, {"copy-storage-inc", VSH_OT_BOOL, 0, N_("migration with non-shared storage with incremental copy (same base image shared between source and destination)")}, + {"change-protection", VSH_OT_BOOL, 0, + N_("prevent any configuration changes to source until migration ends)")}, {"verbose", VSH_OT_BOOL, 0, N_("display the progress of migration")}, {"domain", VSH_OT_DATA, VSH_OFLAG_REQ, N_("domain name, id or uuid")}, {"desturi", VSH_OT_DATA, VSH_OFLAG_REQ, N_("connection URI of the destination host as seen from the client(normal migration) or source(p2p migration)")}, @@ -4906,6 +4908,8 @@ doMigrate (void *opaque) if (vshCommandOptBool (cmd, "copy-storage-inc")) flags |= VIR_MIGRATE_NON_SHARED_INC; + if (vshCommandOptBool (cmd, "change-protection")) + flags |= VIR_MIGRATE_CHANGE_PROTECTION; if (xmlfile && virFileReadAll(xmlfile, 8192, &xml) < 0) diff --git a/tools/virsh.pod b/tools/virsh.pod index e9aaa80..6c3c960 100644 --- a/tools/virsh.pod +++ b/tools/virsh.pod @@ -564,8 +564,9 @@ type attribute for the <domain> element of XML. =item B<migrate> [I<--live>] [I<--direct>] [I<--p2p> [I<--tunnelled>]] [I<--persistent>] [I<--undefinesource>] [I<--suspend>] [I<--copy-storage-all>] -[I<--copy-storage-inc>] [I<--verbose>] I<domain-id> I<desturi> [I<migrateuri>] -[I<dname>] [I<--timeout> B<seconds>] [I<--xml> B<file>] +[I<--copy-storage-inc>] [I<--change-protection>] [I<--verbose>] +I<domain-id> I<desturi> [I<migrateuri>] [I<dname>] +[I<--timeout> B<seconds>] [I<--xml> B<file>] Migrate domain to another host. Add I<--live> for live migration; I<--p2p> for peer-2-peer migration; I<--direct> for direct migration; or I<--tunnelled> @@ -575,6 +576,10 @@ and I<--suspend> leaves the domain paused on the destination host. I<--copy-storage-all> indicates migration with non-shared storage with full disk copy, I<--copy-storage-inc> indicates migration with non-shared storage with incremental copy (same base image shared between source and destination). +I<--change-protection> enforces that no incompatible configuration changes +will be made to the domain while the migration is underway; this flag is +implicitly enabled when supported by the hypervisor, but can be used to +reject the migration if the hypervisor lacks change protection support. I<--verbose> displays the progress of migration. The I<desturi> is the connection URI of the destination host, and -- 1.7.4.4

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Re: [libvirt] [virt-tools-list] virt-manager/libvirt backwards compatibility problem?
by Cole Robinson 27 Jul '11

27 Jul '11

On 07/27/2011 12:28 PM, Whit Blauvelt wrote: > Looks like my real problem may be not incorporating a Debian/Ubuntu patch > before building 0.9.x, since netcat differs: > > https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/517478 > Hmm, what was the error message you were getting? We've made efforts at the libvirt level to have useful error reporting here, so that the cause of failure is more obvious. Also, I patched virt-manager a while ago to use a shell script to handle both RH and debian 'nc' versions. Script is here: http://git.fedorahosted.org/git?p=virt-manager.git;a=blob;f=src/virtManager… Yeah, it's complete and utter crack, but this has been a constant frustration for users, so maybe worth revisiting at the libvirt level (and hey, launching nc over ssh is kinda crack to being with :) ). Even if we solved this in a clean way by providing our own /usr/libexec/libvirt_nc binary, we'd still probably have to play shell script games over SSH to handle connecting to older libvirt (or what if libvirt_nc was installed somewhere other than libexec?) - Cole

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