[libvirt PATCH v5 06/32] qemu: implement persistent file cache for nbdkit caps
Jonathon Jongsma
jjongsma at redhat.com
Tue Feb 14 17:07:53 UTC 2023
Implement the loadFile and saveFile virFileCacheHandlers callbacks so
that nbdkit capabilities are cached perstistently across daemon
restarts. The format and implementation is modeled on the qemu
capabilities, but simplified slightly.
Signed-off-by: Jonathon Jongsma <jjongsma at redhat.com>
Reviewed-by: Peter Krempa <pkrempa at redhat.com>
---
po/POTFILES | 1 +
src/qemu/qemu_nbdkit.c | 226 ++++++++++++++++++++++++++++++++++++++++-
2 files changed, 225 insertions(+), 2 deletions(-)
diff --git a/po/POTFILES b/po/POTFILES
index fa769a8a95..175b3e9fe3 100644
--- a/po/POTFILES
+++ b/po/POTFILES
@@ -180,6 +180,7 @@ src/qemu/qemu_monitor.c
src/qemu/qemu_monitor_json.c
src/qemu/qemu_monitor_text.c
src/qemu/qemu_namespace.c
+src/qemu/qemu_nbdkit.c
src/qemu/qemu_passt.c
src/qemu/qemu_process.c
src/qemu/qemu_qapi.c
diff --git a/src/qemu/qemu_nbdkit.c b/src/qemu/qemu_nbdkit.c
index cd6fe41910..8c37606e2d 100644
--- a/src/qemu/qemu_nbdkit.c
+++ b/src/qemu/qemu_nbdkit.c
@@ -313,11 +313,233 @@ virNbdkitCapsNewData(const char *binary,
}
+static int
+qemuNbdkitCapsValidateBinary(qemuNbdkitCaps *nbdkitCaps,
+ xmlXPathContextPtr ctxt)
+{
+ g_autofree char *str = NULL;
+
+ if (!(str = virXPathString("string(./path)", ctxt))) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("missing path in nbdkit capabilities cache"));
+ return -1;
+ }
+
+ if (STRNEQ(str, nbdkitCaps->path)) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("Expected caps for '%s' but saw '%s'"),
+ nbdkitCaps->path, str);
+ return -1;
+ }
+
+ return 0;
+}
+
+
+static int
+qemuNbdkitCapsParseFlags(qemuNbdkitCaps *nbdkitCaps,
+ xmlXPathContextPtr ctxt)
+{
+ g_autofree xmlNodePtr *nodes = NULL;
+ size_t i;
+ int n;
+
+ if ((n = virXPathNodeSet("./flag", ctxt, &nodes)) < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("failed to parse qemu capabilities flags"));
+ return -1;
+ }
+
+ VIR_DEBUG("Got flags %d", n);
+ for (i = 0; i < n; i++) {
+ unsigned int flag;
+
+ if (virXMLPropEnum(nodes[i], "name", qemuNbdkitCapsTypeFromString,
+ VIR_XML_PROP_REQUIRED, &flag) < 0)
+ return -1;
+
+ qemuNbdkitCapsSet(nbdkitCaps, flag);
+ }
+
+ return 0;
+}
+
+
+/*
+ * Parsing a doc that looks like
+ *
+ * <nbdkitCaps>
+ * <path>/some/path</path>
+ * <nbdkitctime>234235253</nbdkitctime>
+ * <plugindirmtime>234235253</plugindirmtime>
+ * <filterdirmtime>234235253</filterdirmtime>
+ * <selfctime>234235253</selfctime>
+ * <selfvers>1002016</selfvers>
+ * <flag name='foo'/>
+ * <flag name='bar'/>
+ * ...
+ * </nbdkitCaps>
+ *
+ * Returns 0 on success, 1 if outdated, -1 on error
+ */
+static int
+qemuNbdkitCapsLoadCache(qemuNbdkitCaps *nbdkitCaps,
+ const char *filename)
+{
+ g_autoptr(xmlDoc) doc = NULL;
+ g_autoptr(xmlXPathContext) ctxt = NULL;
+ long long int l;
+
+ if (!(doc = virXMLParse(filename, NULL, NULL, "nbdkitCaps", &ctxt, NULL, false)))
+ return -1;
+
+ if (virXPathLongLong("string(./selfctime)", ctxt, &l) < 0) {
+ VIR_DEBUG("missing selfctime in nbdkit capabilities XML");
+ return -1;
+ }
+ nbdkitCaps->libvirtCtime = (time_t)l;
+
+ nbdkitCaps->libvirtVersion = 0;
+ virXPathUInt("string(./selfvers)", ctxt, &nbdkitCaps->libvirtVersion);
+
+ if (nbdkitCaps->libvirtCtime != virGetSelfLastChanged() ||
+ nbdkitCaps->libvirtVersion != LIBVIR_VERSION_NUMBER) {
+ VIR_DEBUG("Outdated capabilities in %s: libvirt changed (%lld vs %lld, %lu vs %lu), stopping load",
+ nbdkitCaps->path,
+ (long long)nbdkitCaps->libvirtCtime,
+ (long long)virGetSelfLastChanged(),
+ (unsigned long)nbdkitCaps->libvirtVersion,
+ (unsigned long)LIBVIR_VERSION_NUMBER);
+ return 1;
+ }
+
+ if (qemuNbdkitCapsValidateBinary(nbdkitCaps, ctxt) < 0)
+ return -1;
+
+ if (virXPathLongLong("string(./nbdkitctime)", ctxt, &l) < 0) {
+ VIR_DEBUG("missing nbdkitctime in nbdkit capabilities XML");
+ return -1;
+ }
+ nbdkitCaps->ctime = (time_t)l;
+
+ if (virXPathLongLong("string(./plugindirmtime)", ctxt, &l) < 0) {
+ VIR_DEBUG("missing plugindirmtime in nbdkit capabilities XML");
+ return -1;
+ }
+ nbdkitCaps->pluginDirMtime = (time_t)l;
+
+ if (virXPathLongLong("string(./filterdirmtime)", ctxt, &l) < 0) {
+ VIR_DEBUG("missing filterdirmtime in nbdkit capabilities XML");
+ return -1;
+ }
+ nbdkitCaps->filterDirMtime = (time_t)l;
+
+ if (qemuNbdkitCapsParseFlags(nbdkitCaps, ctxt) < 0)
+ return -1;
+
+ if ((nbdkitCaps->version = virXPathString("string(./version)", ctxt)) == NULL) {
+ VIR_DEBUG("missing version in nbdkit capabilities cache");
+ return -1;
+ }
+
+ return 0;
+}
+
+
+static void*
+virNbdkitCapsLoadFile(const char *filename,
+ const char *binary,
+ void *privData G_GNUC_UNUSED,
+ bool *outdated)
+{
+ g_autoptr(qemuNbdkitCaps) nbdkitCaps = qemuNbdkitCapsNew(binary);
+ int ret;
+
+ if (!nbdkitCaps)
+ return NULL;
+
+ ret = qemuNbdkitCapsLoadCache(nbdkitCaps, filename);
+ if (ret < 0)
+ return NULL;
+ if (ret == 1) {
+ *outdated = true;
+ return NULL;
+ }
+
+ return g_steal_pointer(&nbdkitCaps);
+}
+
+
+static char*
+qemuNbdkitCapsFormatCache(qemuNbdkitCaps *nbdkitCaps)
+{
+ g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
+ size_t i;
+
+ virBufferAddLit(&buf, "<nbdkitCaps>\n");
+ virBufferAdjustIndent(&buf, 2);
+
+ virBufferEscapeString(&buf, "<path>%s</path>\n",
+ nbdkitCaps->path);
+ virBufferAsprintf(&buf, "<nbdkitctime>%lu</nbdkitctime>\n",
+ nbdkitCaps->ctime);
+ virBufferAsprintf(&buf, "<plugindirmtime>%lu</plugindirmtime>\n",
+ nbdkitCaps->pluginDirMtime);
+ virBufferAsprintf(&buf, "<filterdirmtime>%lu</filterdirmtime>\n",
+ nbdkitCaps->filterDirMtime);
+ virBufferAsprintf(&buf, "<selfctime>%lu</selfctime>\n",
+ nbdkitCaps->libvirtCtime);
+ virBufferAsprintf(&buf, "<selfvers>%u</selfvers>\n",
+ nbdkitCaps->libvirtVersion);
+
+ for (i = 0; i < QEMU_NBDKIT_CAPS_LAST; i++) {
+ if (qemuNbdkitCapsGet(nbdkitCaps, i)) {
+ virBufferAsprintf(&buf, "<flag name='%s'/>\n",
+ qemuNbdkitCapsTypeToString(i));
+ }
+ }
+
+ virBufferAsprintf(&buf, "<version>%s</version>\n",
+ nbdkitCaps->version);
+
+ virBufferAdjustIndent(&buf, -2);
+ virBufferAddLit(&buf, "</nbdkitCaps>\n");
+
+ return virBufferContentAndReset(&buf);
+}
+
+
+static int
+virNbdkitCapsSaveFile(void *data,
+ const char *filename,
+ void *privData G_GNUC_UNUSED)
+{
+ qemuNbdkitCaps *nbdkitCaps = data;
+ g_autofree char *xml = NULL;
+
+ xml = qemuNbdkitCapsFormatCache(nbdkitCaps);
+
+ if (virFileWriteStr(filename, xml, 0600) < 0) {
+ virReportSystemError(errno,
+ _("Failed to save '%s' for '%s'"),
+ filename, nbdkitCaps->path);
+ return -1;
+ }
+
+ VIR_DEBUG("Saved caps '%s' for '%s' with (%lu, %lu)",
+ filename, nbdkitCaps->path,
+ nbdkitCaps->ctime,
+ nbdkitCaps->libvirtCtime);
+
+ return 0;
+}
+
+
virFileCacheHandlers nbdkitCapsCacheHandlers = {
.isValid = virNbdkitCapsIsValid,
.newData = virNbdkitCapsNewData,
- .loadFile = NULL,
- .saveFile = NULL,
+ .loadFile = virNbdkitCapsLoadFile,
+ .saveFile = virNbdkitCapsSaveFile,
.privFree = NULL,
};
--
2.39.1
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