qemu: Unify cached caps validity checks

Let's keep all run time validation of cached QEMU capabilities in
virQEMUCapsIsValid and call it whenever we access the cache.
virQEMUCapsInitCached should keep only the checks which do not make
sense once the cache is loaded in memory.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/qemu_capabilities.c

@@ -3492,25 +3492,21 @@ virQEMUCapsInitCached(virCapsPtr caps,
         VIR_WARN("Failed to load cached caps from '%s' for '%s': %s",
                  capsfile, qemuCaps->binary, virGetLastErrorMessage());
         virResetLastError();
-        ret = 0;
-        virQEMUCapsReset(qemuCaps);
-        goto cleanup;
+        goto discard;
     }
 
+    if (!virQEMUCapsIsValid(qemuCaps, qemuctime))
+        goto discard;
+
     /* Discard cache if QEMU binary or libvirtd changed */
-    if (qemuctime != qemuCaps->ctime ||
-        selfctime != virGetSelfLastChanged() ||
+    if (selfctime != virGetSelfLastChanged() ||
         selfvers != LIBVIR_VERSION_NUMBER) {
-        VIR_DEBUG("Outdated cached capabilities '%s' for '%s' "
-                  "(%lld vs %lld, %lld vs %lld, %lu vs %lu)",
-                  capsfile, qemuCaps->binary,
-                  (long long)qemuCaps->ctime, (long long)qemuctime,
+        VIR_DEBUG("Outdated capabilities for '%s': libvirt changed "
+                  "(%lld vs %lld, %lu vs %lu)",
+                  qemuCaps->binary,
                   (long long)selfctime, (long long)virGetSelfLastChanged(),
                   selfvers, (unsigned long)LIBVIR_VERSION_NUMBER);
-        ignore_value(unlink(capsfile));
-        virQEMUCapsReset(qemuCaps);
-        ret = 0;
-        goto cleanup;
+        goto discard;
     }
 
     VIR_DEBUG("Loaded '%s' for '%s' ctime %lld usedQMP=%d",
@@ -3524,6 +3520,14 @@ virQEMUCapsInitCached(virCapsPtr caps,
     VIR_FREE(capsfile);
     VIR_FREE(capsdir);
     return ret;
+
+ discard:
+    VIR_DEBUG("Dropping cached capabilities '%s' for '%s'",
+              capsfile, qemuCaps->binary);
+    ignore_value(unlink(capsfile));
+    virQEMUCapsReset(qemuCaps);
+    ret = 0;
+    goto cleanup;
 }
 
 
@@ -4076,17 +4080,35 @@ virQEMUCapsNewForBinary(virCapsPtr caps,
 }
 
 
-bool virQEMUCapsIsValid(virQEMUCapsPtr qemuCaps)
+bool
+virQEMUCapsIsValid(virQEMUCapsPtr qemuCaps,
+                   time_t ctime)
 {
-    struct stat sb;
-
     if (!qemuCaps->binary)
         return true;
 
-    if (stat(qemuCaps->binary, &sb) < 0)
+    if (!ctime) {
+        struct stat sb;
+
+        if (stat(qemuCaps->binary, &sb) < 0) {
+            char ebuf[1024];
+            VIR_DEBUG("Failed to stat QEMU binary '%s': %s",
+                      qemuCaps->binary,
+                      virStrerror(errno, ebuf, sizeof(ebuf)));
+            return false;
+        }
+        ctime = sb.st_ctime;
+    }
+
+    if (ctime != qemuCaps->ctime) {
+        VIR_DEBUG("Outdated capabilities for '%s': QEMU binary changed "
+                  "(%lld vs %lld)",
+                  qemuCaps->binary,
+                  (long long) ctime, (long long) qemuCaps->ctime);
         return false;
+    }
 
-    return sb.st_ctime == qemuCaps->ctime;
+    return true;
 }
 
 
@@ -4179,7 +4201,7 @@ virQEMUCapsCacheLookup(virCapsPtr caps,
     virMutexLock(&cache->lock);
     ret = virHashLookup(cache->binaries, binary);
     if (ret &&
-        !virQEMUCapsIsValid(ret)) {
+        !virQEMUCapsIsValid(ret, 0)) {
         VIR_DEBUG("Cached capabilities %p no longer valid for %s",
                   ret, binary);
         virHashRemoveEntry(cache->binaries, binary);

src/qemu/qemu_capabilities.h

@@ -451,7 +451,8 @@ int virQEMUCapsGetMachineTypesCaps(virQEMUCapsPtr qemuCaps,
                                    size_t *nmachines,
                                    virCapsGuestMachinePtr **machines);
 
-bool virQEMUCapsIsValid(virQEMUCapsPtr qemuCaps);
+bool virQEMUCapsIsValid(virQEMUCapsPtr qemuCaps,
+                        time_t ctime);
 
 void virQEMUCapsFilterByMachineType(virQEMUCapsPtr qemuCaps,
                                     const char *machineType);