Re: [libvirt PATCH 4/4] conf: add control over COW for storage pool directories

The storage pool code now attempts to disable COW by default on btrfs, but management applications may wish to override this behaviour. Thus we introduce a concept of storage pool features: <features> <cow state='yes|no'/> </features> If the <cow> feature policy is set, it will be enforced. It will always return an hard error if COW cannot be explicitly set or unset. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- docs/formatstorage.html.in | 25 ++++++++++ docs/schemas/storagepool.rng | 30 ++++++++++++ src/conf/storage_conf.c | 49 ++++++++++++++++++++ src/conf/storage_conf.h | 8 ++++ src/storage/storage_util.c | 2 +- tests/storagepoolxml2xmlin/pool-dir-cow.xml | 10 ++++ tests/storagepoolxml2xmlout/pool-dir-cow.xml | 15 ++++++ tests/storagepoolxml2xmltest.c | 1 + 8 files changed, 139 insertions(+), 1 deletion(-) create mode 100644 tests/storagepoolxml2xmlin/pool-dir-cow.xml create mode 100644 tests/storagepoolxml2xmlout/pool-dir-cow.xml

diff --git a/src/conf/storage_conf.c b/src/conf/storage_conf.c index 65d9b33049..4e63865b39 100644 --- a/src/conf/storage_conf.c +++ b/src/conf/storage_conf.c @@ -839,6 +839,33 @@ virStoragePoolDefRefreshFormat(virBufferPtr buf, } +static int +virStoragePoolDefParseFeatures(virStoragePoolDefPtr def, + xmlXPathContextPtr ctxt) +{ + g_autofree char *cow = virXPathString("string(./features/cow/@state)", ctxt); + + if (cow) { + int val; + if (def->type != VIR_STORAGE_POOL_FS && + def->type != VIR_STORAGE_POOL_DIR) { + virReportError(VIR_ERR_NO_SUPPORT, "%s", + _("cow feature may only be used for 'fs' and 'dir' pools")); + return -1; + } + if ((val = virTristateBoolTypeFromString(cow)) < 0) {

+ virReportError(VIR_ERR_XML_ERROR, + _("invalid storage pool cow feature state '%s'"), + cow); + return -1; + } + def->features.cow = val; + } + + return 0; +} + + virStoragePoolDefPtr virStoragePoolDefParseXML(xmlXPathContextPtr ctxt) { @@ -910,6 +937,9 @@ virStoragePoolDefParseXML(xmlXPathContextPtr ctxt) } } + if (virStoragePoolDefParseFeatures(def, ctxt) < 0) + return NULL; + if (options->flags & VIR_STORAGE_POOL_SOURCE_HOST) { if (!def->source.nhost) { virReportError(VIR_ERR_XML_ERROR, "%s", @@ -1131,6 +1161,23 @@ virStoragePoolSourceFormat(virBufferPtr buf, } +static void +virStoragePoolDefFormatFeatures(virBufferPtr buf, + virStoragePoolDefPtr def) +{ + if (!def->features.cow) + return; + + virBufferAddLit(buf, "<features>\n"); + virBufferAdjustIndent(buf, 2); + if (def->features.cow)

+ virBufferAsprintf(buf, "<cow state='%s'/>\n", + virTristateBoolTypeToString(def->features.cow)); + virBufferAdjustIndent(buf, -2); + virBufferAddLit(buf, "</features>\n"); +}