2:16 p.m.
On 4/17/24 09:29, Andrea Bolognani wrote:
As explained in the comment, this can help in scenarios where
a shared filesystem can't be detected as such by libvirt, by
giving the admin the opportunity to provide this information
manually.
Signed-off-by: Andrea Bolognani <abologna(a)redhat.com>
---
src/qemu/libvirtd_qemu.aug | 3 +++
src/qemu/qemu.conf.in | 23 +++++++++++++++++++++++
src/qemu/qemu_conf.c | 17 +++++++++++++++++
src/qemu/qemu_conf.h | 2 ++
src/qemu/test_libvirtd_qemu.aug.in | 5 +++++
5 files changed, 50 insertions(+)
diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug
index 2b6526538f..1377fd89cc 100644
--- a/src/qemu/libvirtd_qemu.aug
+++ b/src/qemu/libvirtd_qemu.aug
@@ -143,6 +143,8 @@ module Libvirtd_qemu =
let storage_entry = bool_entry "storage_use_nbdkit"
+ let filesystem_entry = str_array_entry "shared_filesystems"
+
(* Entries that used to exist in the config which are now
* deleted. We keep on parsing them so we don't break
* ability to parse old configs after upgrade
@@ -173,6 +175,7 @@ module Libvirtd_qemu =
| swtpm_entry
| capability_filters_entry
| storage_entry
+ | filesystem_entry
| obsolete_entry
let comment = [ label "#comment" . del /#[ \t]*/ "# " . store
/([^ \t\n][^\n]*)?/ . del /\n/ "\n" ]
diff --git a/src/qemu/qemu.conf.in b/src/qemu/qemu.conf.in
index f406df8749..c543a0a55b 100644
--- a/src/qemu/qemu.conf.in
+++ b/src/qemu/qemu.conf.in
@@ -986,3 +986,26 @@
# note that the default might change in future releases.
#
#storage_use_nbdkit = @USE_NBDKIT_DEFAULT@
+
+# libvirt will normally prevent migration if the storage backing the VM is not
+# on a shared filesystems. Sometimes, however, the storage *is* shared despite
+# not being detected as such: for example, this is the case when one of the
+# hosts involved in the migration is exporting its local storage to the other
+# one via NFS.
+#
+# Any directory listed here will be assumed to live on a shared filesystem,
+# making migration possible in scenarios such as the one described above.
+#
+# Due to how label remembering is implemented, it will generally be necessary
+# to set remember_owner=0 *on both sides of the migration* as well.
+#
+# NOTE: this option is intended to help in very specific scenarios that are
+# rarely encountered. If you find yourself reaching for this option, consider
+# reworking your environment so that it follows a more common architecture
+# rather than using it.
+#
+#shared_filesystems = [
+# "/path/to/images",
+# "/path/to/nvram",
+# "/path/to/swtpm"
+#]
May be worth considering: Would it ever be useful or necessary for
libvirt to know what type of filesystem is used for the sharing, so that
users should write nfs:/path/to/swtpm for example? I don't have much
experience with shared filesystems (other than NFS) but maybe sometimes
behavior has to be adjusted depending on what type is being used.
Otherwise LGTM.
> diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
> index 4050a82341..01c6bcc793 100644
> --- a/src/qemu/qemu_conf.c
> +++ b/src/qemu/qemu_conf.c
> @@ -374,6 +374,8 @@ static void virQEMUDriverConfigDispose(void *obj)
>
> g_strfreev(cfg->capabilityfilters);
>
> + g_strfreev(cfg->sharedFilesystems);
> +
> g_free(cfg->deprecationBehavior);
> }
>
> @@ -1084,6 +1086,18 @@ virQEMUDriverConfigLoadStorageEntry(virQEMUDriverConfig *cfg,
> }
>
>
> +static int
> +virQEMUDriverConfigLoadFilesystemEntry(virQEMUDriverConfig *cfg,
> + virConf *conf)
> +{
> + if (virConfGetValueStringList(conf, "shared_filesystems", false,
> + &cfg->sharedFilesystems) < 0)
> + return -1;
> +
> + return 0;
> +}
> +
> +
> int virQEMUDriverConfigLoadFile(virQEMUDriverConfig *cfg,
> const char *filename,
> bool privileged)
> @@ -1158,6 +1172,9 @@ int virQEMUDriverConfigLoadFile(virQEMUDriverConfig *cfg,
> if (virQEMUDriverConfigLoadStorageEntry(cfg, conf) < 0)
> return -1;
>
> + if (virQEMUDriverConfigLoadFilesystemEntry(cfg, conf) < 0)
> + return -1;
> +
> return 0;
> }
>
> diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
> index 36049b4bfa..b53d56be02 100644
> --- a/src/qemu/qemu_conf.h
> +++ b/src/qemu/qemu_conf.h
> @@ -233,6 +233,8 @@ struct _virQEMUDriverConfig {
> bool storageUseNbdkit;
>
> virQEMUSchedCore schedCore;
> +
> + char **sharedFilesystems;
> };
>
> G_DEFINE_AUTOPTR_CLEANUP_FUNC(virQEMUDriverConfig, virObjectUnref);
> diff --git a/src/qemu/test_libvirtd_qemu.aug.in b/src/qemu/test_libvirtd_qemu.aug.in
> index b97e6de11e..69fdae215a 100644
> --- a/src/qemu/test_libvirtd_qemu.aug.in
> +++ b/src/qemu/test_libvirtd_qemu.aug.in
> @@ -119,3 +119,8 @@ module Test_libvirtd_qemu =
> { "deprecation_behavior" = "none" }
> { "sched_core" = "none" }
> { "storage_use_nbdkit" = "@USE_NBDKIT_DEFAULT@" }
> +{ "shared_filesystems"
> + { "1" = "/path/to/images" }
> + { "2" = "/path/to/nvram" }
> + { "3" = "/path/to/swtpm" }
> +}