From 4d34c92947e8cf9e9bedfa227ada1d2dba92d68a Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 9 Oct 2012 16:08:14 -0600 Subject: [PATCH] storage: cache backing chain while qemu domain is live Technically, we should not be re-probing any file that qemu might be currently writing to. As such, we should cache the backing file chain prior to starting qemu. This patch adds the cache, but does not use it until the next patch. Ultimately, we want to also store the chain in domain XML, so that it is remembered across libvirtd restarts, and so that the only kosher way to modify the backing chain of an offline domain will be through libvirt API calls, but we aren't there yet. So for now, we merely invalidate the cache any time we do a live operation that alters the chain (block-pull, block-commit, external disk snapshot), as well as tear down the cache when the domain is not running. * src/conf/domain_conf.h (_virDomainDiskDef): New field. * src/conf/domain_conf.c (virDomainDiskDefFree): Clean new field. * src/qemu/qemu_domain.h (qemuDomainDetermineDiskChain): New prototype. * src/qemu/qemu_domain.c (qemuDomainDetermineDiskChain): New function. * src/qemu/qemu_driver.c (qemuDomainAttachDeviceDiskLive) (qemuDomainChangeDiskMediaLive): Pre-populate chain. (qemuDomainSnapshotCreateSingleDiskActive): Uncache chain before snapshot. * src/qemu/qemu_process.c (qemuProcessHandleBlockJob): Update chain after block pull. --- src/conf/domain_conf.c | 1 + src/conf/domain_conf.h | 2 ++ src/qemu/qemu_domain.c | 26 ++++++++++++++++++++++++++ src/qemu/qemu_domain.h | 3 +++ src/qemu/qemu_driver.c | 14 ++++++++++++++ src/qemu/qemu_process.c | 8 ++++++++ 6 files changed, 54 insertions(+) diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 7618468c21..71d1666c54 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -975,6 +975,7 @@ void virDomainDiskDefFree(virDomainDiskDefPtr def) VIR_FREE(def->src); VIR_FREE(def->dst); VIR_FREE(def->driverName); + virStorageFileFreeMetadata(def->backingChain); VIR_FREE(def->mirror); VIR_FREE(def->auth.username); VIR_FREE(def->wwn); diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index 039e34ddc1..6e6b259d10 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -47,6 +47,7 @@ # include "virobject.h" # include "device_conf.h" # include "bitmap.h" +# include "storage_file.h" /* forward declarations of all device types, required by * virDomainDeviceDef @@ -568,6 +569,7 @@ struct _virDomainDiskDef { } auth; char *driverName; int format; /* enum virStorageFileFormat */ + virStorageFileMetadataPtr backingChain; char *mirror; int mirrorFormat; /* enum virStorageFileFormat */ diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index fb775c13c7..4e6a5e93a8 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -2012,3 +2012,29 @@ qemuDomainCleanupRun(struct qemud_driver *driver, priv->ncleanupCallbacks = 0; priv->ncleanupCallbacks_max = 0; } + +int +qemuDomainDetermineDiskChain(struct qemud_driver *driver, + virDomainDiskDefPtr disk, + bool force) +{ + bool probe = driver->allowDiskFormatProbing; + + if (!disk->src) + return 0; + + if (disk->backingChain) { + if (force) { + virStorageFileFreeMetadata(disk->backingChain); + disk->backingChain = NULL; + } else { + return 0; + } + } + disk->backingChain = virStorageFileGetMetadata(disk->src, disk->format, + driver->user, driver->group, + probe); + if (!disk->backingChain) + return -1; + return 0; +} diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h index 26b6c557c0..8a66f14ec9 100644 --- a/src/qemu/qemu_domain.h +++ b/src/qemu/qemu_domain.h @@ -343,6 +343,9 @@ bool qemuDomainJobAllowed(qemuDomainObjPrivatePtr priv, int qemuDomainCheckDiskPresence(struct qemud_driver *driver, virDomainObjPtr vm, bool start_with_state); +int qemuDomainDetermineDiskChain(struct qemud_driver *driver, + virDomainDiskDefPtr disk, + bool force); int qemuDomainCleanupAdd(virDomainObjPtr vm, qemuDomainCleanupCallback cb); diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 6de65ea825..c3e4fd4a71 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -5816,6 +5816,9 @@ qemuDomainAttachDeviceDiskLive(virConnectPtr conn, goto end; } + if (qemuDomainDetermineDiskChain(driver, disk, false) < 0) + goto end; + if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_DEVICES)) { if (virCgroupForDomain(driver->cgroup, vm->def->name, &cgroup, 0)) { virReportError(VIR_ERR_INTERNAL_ERROR, @@ -6044,6 +6047,9 @@ qemuDomainChangeDiskMediaLive(virDomainObjPtr vm, virCgroupPtr cgroup = NULL; int ret = -1; + if (qemuDomainDetermineDiskChain(driver, disk, false) < 0) + goto end; + if (qemuCgroupControllerActive(driver, VIR_CGROUP_CONTROLLER_DEVICES)) { if (virCgroupForDomain(driver->cgroup, vm->def->name, &cgroup, 0) != 0) { @@ -10789,6 +10795,14 @@ qemuDomainSnapshotCreateSingleDiskActive(struct qemud_driver *driver, disk->src = source; origdriver = disk->format; disk->format = VIR_STORAGE_FILE_RAW; /* Don't want to probe backing files */ + /* XXX Here, we know we are about to alter disk->backingChain if + * successful, so we nuke the existing chain so that future + * commands will recompute it. Better would be storing the chain + * ourselves rather than reprobing, but this requires modifying + * domain_conf and our XML to fully track the chain across + * libvirtd restarts. */ + virStorageFileFreeMetadata(disk->backingChain); + disk->backingChain = NULL; if (virDomainLockDiskAttach(driver->lockManager, driver->uri, vm, disk) < 0) diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c index d3951d1326..0628621cb5 100644 --- a/src/qemu/qemu_process.c +++ b/src/qemu/qemu_process.c @@ -909,6 +909,14 @@ qemuProcessHandleBlockJob(qemuMonitorPtr mon ATTRIBUTE_UNUSED, if (disk) { path = disk->src; event = virDomainEventBlockJobNewFromObj(vm, path, type, status); + /* XXX If we completed a block pull, then recompute the cached + * backing chain to match. Better would be storing the chain + * ourselves rather than reprobing, but this requires + * modifying domain_conf and our XML to fully track the chain + * across libvirtd restarts. */ + if (type == VIR_DOMAIN_BLOCK_JOB_TYPE_PULL && + status == VIR_DOMAIN_BLOCK_JOB_COMPLETED) + qemuDomainDetermineDiskChain(driver, disk, true); } virDomainObjUnlock(vm);