drbd: allow status dump request all volumes of a specific resource

We had drbd_adm_get_status (one single volume),
and drbd_adm_get_status_all (dump of all volumes of all resources).

This enhances the latter to be able to dump all volumes
of just one specific resource.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 66 insertions, 4 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index f86e882efcac..fff11ae79f15 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -2598,7 +2598,7 @@ out:
         return 0;
 }
 
-int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
+int get_one_status(struct sk_buff *skb, struct netlink_callback *cb)
 {
         struct drbd_conf *mdev;
         struct drbd_genlmsghdr *dh;
@@ -2616,6 +2616,9 @@ int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
          * where tconn is cb->args[0];
          * and i is cb->args[1];
          *
+         * cb->args[2] indicates if we shall loop over all resources,
+         * or just dump all volumes of a single resource.
+         *
          * This may miss entries inserted after this dump started,
          * or entries deleted before they are reached.
          *
@@ -2626,7 +2629,6 @@ int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
 
         /* synchronize with drbd_new_tconn/drbd_free_tconn */
         down_read(&drbd_cfg_rwsem);
-next_tconn:
         /* revalidate iterator position */
         list_for_each_entry(tmp, &drbd_tconns, all_tconn) {
                 if (pos == NULL) {
@@ -2641,16 +2643,22 @@ next_tconn:
                 }
         }
         if (tconn) {
+next_tconn:
                 mdev = idr_get_next(&tconn->volumes, &volume);
                 if (!mdev) {
                         /* No more volumes to dump on this tconn.
                          * Advance tconn iterator. */
                         pos = list_entry(tconn->all_tconn.next,
                                         struct drbd_tconn, all_tconn);
-                        /* But, did we dump any volume on this tconn yet? */
+                        /* Did we dump any volume on this tconn yet? */
                         if (volume != 0) {
-                                tconn = NULL;
+                                /* If we reached the end of the list,
+                                 * or only a single resource dump was requested,
+                                 * we are done. */
+                                if (&pos->all_tconn == &drbd_tconns || cb->args[2])
+                                        goto out;
                                 volume = 0;
+                                tconn = pos;
                                 goto next_tconn;
                         }
                 }
@@ -2696,6 +2704,60 @@ out:
         return skb->len;
 }
 
+/*
+ * Request status of all resources, or of all volumes within a single resource.
+ *
+ * This is a dump, as the answer may not fit in a single reply skb otherwise.
+ * Which means we cannot use the family->attrbuf or other such members, because
+ * dump is NOT protected by the genl_lock().  During dump, we only have access
+ * to the incoming skb, and need to opencode "parsing" of the nlattr payload.
+ *
+ * Once things are setup properly, we call into get_one_status().
+ */
+int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
+{
+        const unsigned hdrlen = GENL_HDRLEN + GENL_MAGIC_FAMILY_HDRSZ;
+        struct nlattr *nla;
+        const char *conn_name;
+        struct drbd_tconn *tconn;
+
+        /* Is this a followup call? */
+        if (cb->args[0]) {
+                /* ... of a single resource dump,
+                 * and the resource iterator has been advanced already? */
+                if (cb->args[2] && cb->args[2] != cb->args[0])
+                        return 0; /* DONE. */
+                goto dump;
+        }
+
+        /* First call (from netlink_dump_start).  We need to figure out
+         * which resource(s) the user wants us to dump. */
+        nla = nla_find(nlmsg_attrdata(cb->nlh, hdrlen),
+                        nlmsg_attrlen(cb->nlh, hdrlen),
+                        DRBD_NLA_CFG_CONTEXT);
+
+        /* No explicit context given.  Dump all. */
+        if (!nla)
+                goto dump;
+        nla = nla_find_nested(nla, __nla_type(T_ctx_conn_name));
+        /* context given, but no name present? */
+        if (!nla)
+                return -EINVAL;
+        conn_name = nla_data(nla);
+        tconn = conn_by_name(conn_name);
+        if (!tconn)
+                return -ENODEV;
+
+        /* prime iterators, and set "filter" mode mark:
+         * only dump this tconn. */
+        cb->args[0] = (long)tconn;
+        /* cb->args[1] = 0; passed in this way. */
+        cb->args[2] = (long)tconn;
+
+dump:
+        return get_one_status(skb, cb);
+}
+
 int drbd_adm_get_timeout_type(struct sk_buff *skb, struct genl_info *info)
 {
         enum drbd_ret_code retcode;