[libvirt] [PATCH] storage: Adjust qemu-img switches check

[John Ferlan]

Since we support QEMU 0.12 and later, checking for support of specific flags
added prior to that isn't necessary.

Thus start with the base of having the "-o options" available for the
qemu-img create option and then determine whether we have the compat
option for qcow2 files (which would be necessary up through qemu 2.0
where the default changes to compat 0.11).

NOTE: Keeping old tests around since it's still possible to create in
the old format.

Signed-off-by: John Ferlan <jferlan at redhat.com>
---
 src/storage/storage_backend.c | 66 ++++++++++++++++---------------------------
 1 file changed, 24 insertions(+), 42 deletions(-)

diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c
index 3a23cd7..eaa6f65 100644
--- a/src/storage/storage_backend.c
+++ b/src/storage/storage_backend.c
@@ -869,9 +869,19 @@ virStoragePloopResize(virStorageVolDefPtr vol,
     return ret;
 }
 
+/* Flag values shared w/ storagevolxml2argvtest.c.
+ * Since it's still possible to provide the old format args, just
+ * keep them; however, prefix with an "X_" (similar to qemu_capabilities.c)
+ * to indicate the are older.
+ *
+ * QEMU_IMG_BACKING_FORMAT_OPTIONS (added in qemu 0.11)
+ * QEMU_IMG_BACKING_FORMAT_OPTIONS_COMPAT
+ *    was made necessary due to 2.0 change to change the default
+ *    qcow2 file format from 0.10 to 1.1.
+ */
 enum {
-    QEMU_IMG_BACKING_FORMAT_NONE = 0,
-    QEMU_IMG_BACKING_FORMAT_FLAG,
+    X_QEMU_IMG_BACKING_FORMAT_NONE = 0,
+    X_QEMU_IMG_BACKING_FORMAT_FLAG,
     QEMU_IMG_BACKING_FORMAT_OPTIONS,
     QEMU_IMG_BACKING_FORMAT_OPTIONS_COMPAT,
 };
@@ -904,46 +914,18 @@ virStorageBackendQemuImgSupportsCompat(const char *qemuimg)
 static int
 virStorageBackendQEMUImgBackingFormat(const char *qemuimg)
 {
-    char *help = NULL;
-    char *start;
-    char *end;
-    char *tmp;
-    int ret = -1;
-    int exitstatus;
-    virCommandPtr cmd = virCommandNewArgList(qemuimg, "-h", NULL);
-
-    virCommandAddEnvString(cmd, "LC_ALL=C");
-    virCommandSetOutputBuffer(cmd, &help);
-    virCommandClearCaps(cmd);
-
-    /* qemuimg doesn't return zero exit status on -h,
-     * therefore we need to provide pointer for storing
-     * exit status, although we don't parse it any later */
-    if (virCommandRun(cmd, &exitstatus) < 0)
-        goto cleanup;
+    /* As of QEMU 0.11 the [-o options] support was added via qemu
+     * commit id '9ea2ea71', so we start with that base and figure
+     * out what else we have */
+    int ret = QEMU_IMG_BACKING_FORMAT_OPTIONS;
+
+    /* QEMU 2.0 changed to using a format that only QEMU 1.1 and newer
+     * understands. Since we still support QEMU 0.12 and newer, we need
+     * to be able to handle the previous format as can be set via a
+     * compat=0.10 option. */
+    if (virStorageBackendQemuImgSupportsCompat(qemuimg))
+        ret = QEMU_IMG_BACKING_FORMAT_OPTIONS_COMPAT;
 
-    if ((start = strstr(help, " create ")) == NULL ||
-        (end = strstr(start, "\n")) == NULL) {
-        virReportError(VIR_ERR_INTERNAL_ERROR,
-                       _("unable to parse qemu-img output '%s'"),
-                       help);
-        goto cleanup;
-    }
-    if (((tmp = strstr(start, "-F fmt")) && tmp < end) ||
-        ((tmp = strstr(start, "-F backing_fmt")) && tmp < end)) {
-        ret = QEMU_IMG_BACKING_FORMAT_FLAG;
-    } else if ((tmp = strstr(start, "[-o options]")) && tmp < end) {
-        if (virStorageBackendQemuImgSupportsCompat(qemuimg))
-            ret = QEMU_IMG_BACKING_FORMAT_OPTIONS_COMPAT;
-        else
-            ret = QEMU_IMG_BACKING_FORMAT_OPTIONS;
-    } else {
-        ret = QEMU_IMG_BACKING_FORMAT_NONE;
-    }
-
- cleanup:
-    virCommandFree(cmd);
-    VIR_FREE(help);
     return ret;
 }
 
@@ -1196,7 +1178,7 @@ virStorageBackendCreateQemuImgCmdFromVol(virConnectPtr conn,
         VIR_FREE(opts);
     } else {
         if (info.backingPath) {
-            if (imgformat == QEMU_IMG_BACKING_FORMAT_FLAG)
+            if (imgformat == X_QEMU_IMG_BACKING_FORMAT_FLAG)
                 virCommandAddArgList(cmd, "-F", backingType, NULL);
             else
                 VIR_DEBUG("Unable to set backing store format for %s with %s",
-- 
2.5.5