rbd: fix ceph settings precedence

Apply the ceph settings from a config file before any ceph settings
from the command line. Since the ceph config file location may be
specified on the command line, parse it once to read the config file,
and do a second pass to apply the rest of the command line ceph
options.

Signed-off-by: Josh Durgin <jdurgin@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/rbd.c

diff --git a/block/rbd.c b/block/rbd.c
index 00d027d..a60a19d 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -228,7 +228,9 @@
     return NULL;
 }
 
-static int qemu_rbd_set_conf(rados_t cluster, const char *conf, Error **errp)
+static int qemu_rbd_set_conf(rados_t cluster, const char *conf,
+                             bool only_read_conf_file,
+                             Error **errp)
 {
     char *p, *buf;
     char name[RBD_MAX_CONF_NAME_SIZE];
@@ -260,14 +262,18 @@
         qemu_rbd_unescape(value);
 
         if (strcmp(name, "conf") == 0) {
-            ret = rados_conf_read_file(cluster, value);
-            if (ret < 0) {
-                error_setg(errp, "error reading conf file %s", value);
-                break;
+            /* read the conf file alone, so it doesn't override more
+               specific settings for a particular device */
+            if (only_read_conf_file) {
+                ret = rados_conf_read_file(cluster, value);
+                if (ret < 0) {
+                    error_setg(errp, "error reading conf file %s", value);
+                    break;
+                }
             }
         } else if (strcmp(name, "id") == 0) {
             /* ignore, this is parsed by qemu_rbd_parse_clientname() */
-        } else {
+        } else if (!only_read_conf_file) {
             ret = rados_conf_set(cluster, name, value);
             if (ret < 0) {
                 error_setg(errp, "invalid conf option %s", name);
@@ -330,10 +336,15 @@
     if (strstr(conf, "conf=") == NULL) {
         /* try default location, but ignore failure */
         rados_conf_read_file(cluster, NULL);
+    } else if (conf[0] != '\0' &&
+               qemu_rbd_set_conf(cluster, conf, true, &local_err) < 0) {
+        rados_shutdown(cluster);
+        error_propagate(errp, local_err);
+        return -EIO;
     }
 
     if (conf[0] != '\0' &&
-        qemu_rbd_set_conf(cluster, conf, &local_err) < 0) {
+        qemu_rbd_set_conf(cluster, conf, false, &local_err) < 0) {
         rados_shutdown(cluster);
         error_propagate(errp, local_err);
         return -EIO;
@@ -463,10 +474,15 @@
     if (strstr(conf, "conf=") == NULL) {
         /* try default location, but ignore failure */
         rados_conf_read_file(s->cluster, NULL);
+    } else if (conf[0] != '\0') {
+        r = qemu_rbd_set_conf(s->cluster, conf, true, errp);
+        if (r < 0) {
+            goto failed_shutdown;
+        }
     }
 
     if (conf[0] != '\0') {
-        r = qemu_rbd_set_conf(s->cluster, conf, errp);
+        r = qemu_rbd_set_conf(s->cluster, conf, false, errp);
         if (r < 0) {
             goto failed_shutdown;
         }