[libvirt] [PATCH 6/8] qemu: Unify cached caps validity checks

[Jiri Denemark]

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: Jiri Denemark <jdenemar at redhat.com>
---
 src/qemu/qemu_capabilities.c | 59 ++++++++++++++++++++++++++++++--------------
 src/qemu/qemu_capabilities.h |  3 ++-
 2 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 91e8b30..d1c31ad 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -3516,25 +3516,21 @@ 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-        VIR_DEBUG("Outdated cached capabilities '%s' for '%s' "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)",
+        VIR_DEBUG("Dropping cached capabilities '%s' for '%s': "
+                  "libvirt changed (%lld vs %lld, %lu vs %lu)",
                   capsfile, qemuCaps->binary,
-                  (long long)qemuCaps->ctime, (long long)qemuctime,
                   (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",
@@ -3548,6 +3544,12 @@ virQEMUCapsInitCached(virCapsPtr caps,
     VIR_FREE(capsfile);
     VIR_FREE(capsdir);
     return ret;
+
+ discard:
+    ignore_value(unlink(capsfile));
+    virQEMUCapsReset(qemuCaps);
+    ret = 0;
+    goto cleanup;
 }
 
 
@@ -4111,17 +4113,36 @@ 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)
-        return false;
+    if (!ctime) {
+        struct stat sb;
 
-    return sb.st_ctime == qemuCaps->ctime;
+        if (stat(qemuCaps->binary, &sb) < 0) {
+            char ebuf[1024];
+            VIR_DEBUG("Dropping cached capabilities for '%s': "
+                      "failed to stat QEMU binary: %s",
+                      qemuCaps->binary,
+                      virStrerror(errno, ebuf, sizeof(ebuf)));
+            return false;
+        }
+        ctime = sb.st_ctime;
+    }
+
+    if (ctime != qemuCaps->ctime) {
+        VIR_DEBUG("Dropping cached capabilities for '%s': "
+                  "binary is newer than cache (%lld vs %lld)",
+                  qemuCaps->binary,
+                  (long long) ctime, (long long) qemuCaps->ctime);
+        return false;
+    }
+
+    return true;
 }
 
 
@@ -4214,7 +4235,7 @@ 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);
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index c77ba13..6c45a67 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -449,7 +449,8 @@ 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);
-- 
2.10.2