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qemu: handle adding/removing nbdkit-backed disk sources

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Previously we were only starting or stopping nbdkit when the guest was
started or stopped or when hotplugging/unplugging a disk. But when doing
block operations, the disk backing store sources can also be be added or
removed independently of the disk device. When this happens the nbdkit
backend was not being handled properly. For example, when doing a
blockcopy from a nbdkit-backed disk to a new disk and pivoting to that
new location, the nbdkit process did not get cleaned up properly. Add
some functionality to qemuDomainStorageSourceAccessModify() to handle
this scenario.

Since we're now starting nbdkit from the ChainAccessAllow/Revoke()
functions, we no longer need to explicitly start nbdkit in hotplug code
paths because the hotplug functions already call these allow/revoke
functions and will start/stop nbdkit if necessary.

Add a check to qemuNbdkitProcessStart() to report an error if we
are trying to start nbdkit for a disk source that already has a running
nbdkit process. This shouldn't happen, and if it does it indicates an
error in another part of our code.

Signed-off-by: Jonathon Jongsma <jjongsma@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
This commit is contained in:
Jonathon Jongsma 2024-01-25 11:51:51 -06:00
parent 4495ec7d9b
commit 94365a4871
3 changed files with 17 additions and 5 deletions
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10
src/qemu/qemu_domain.c
View File

@ -8060,6 +8060,7 @@ qemuDomainStorageSourceAccessModify(virQEMUDriver *driver,
bool revoke_namespace = false;
bool revoke_nvme = false;
bool revoke_lockspace = false;
bool revoke_nbdkit = false;
VIR_DEBUG("src='%s' readonly=%d force_ro=%d force_rw=%d revoke=%d chain=%d",
NULLSTR(src->path), src->readonly, force_ro, force_rw, revoke, chain);
@ -8078,6 +8079,7 @@ qemuDomainStorageSourceAccessModify(virQEMUDriver *driver,
revoke_namespace = true;
revoke_nvme = true;
revoke_lockspace = true;
revoke_nbdkit = true;
ret = 0;
goto revoke;
}
@ -8093,6 +8095,11 @@ qemuDomainStorageSourceAccessModify(virQEMUDriver *driver,
revoke_nvme = true;
if (qemuNbdkitStartStorageSource(driver, vm, src, chain) < 0)
goto revoke;
revoke_nbdkit = true;
if (qemuDomainNamespaceSetupDisk(vm, src, &revoke_namespace) < 0)
goto revoke;
}
@ -8147,6 +8154,9 @@ qemuDomainStorageSourceAccessModify(virQEMUDriver *driver,
VIR_WARN("Unable to release lock on %s", srcstr);
}
if (revoke_nbdkit)
qemuNbdkitStopStorageSource(src, vm, chain);
cleanup:
src->readonly = was_readonly;
virErrorRestore(&orig_err);

5
src/qemu/qemu_hotplug.c
View File

@ -1023,9 +1023,6 @@ qemuDomainAttachDeviceDiskLiveInternal(virQEMUDriver *driver,
if (qemuHotplugAttachManagedPR(vm, disk->src, VIR_ASYNC_JOB_NONE) < 0)
goto cleanup;
if (qemuNbdkitStartStorageSource(driver, vm, disk->src, true) < 0)
goto cleanup;
}
ret = qemuDomainAttachDiskGeneric(vm, disk, VIR_ASYNC_JOB_NONE);
@ -1050,8 +1047,6 @@ qemuDomainAttachDeviceDiskLiveInternal(virQEMUDriver *driver,
if (virStorageSourceChainHasManagedPR(disk->src))
ignore_value(qemuHotplugRemoveManagedPR(vm, VIR_ASYNC_JOB_NONE));
qemuNbdkitStopStorageSource(disk->src, vm, true);
}
qemuDomainSecretDiskDestroy(disk);
qemuDomainCleanupStorageSourceFD(disk->src);

7
src/qemu/qemu_nbdkit.c
View File

@ -1190,6 +1190,13 @@ qemuNbdkitProcessStart(qemuNbdkitProcess *proc,
struct nbd_handle *nbd = NULL;
#endif
/* don't try to start nbdkit again if we've already started it */
if (proc->pid > 0) {
virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
_("Attempting to start nbdkit twice"));
return -1;
}
if (!(cmd = qemuNbdkitProcessBuildCommand(proc)))
return -1;