[xen staging] tools/xenstore: fire watches only when removing a specific node

[patchbot@xxxxxxx]

commit 1e5815697f941d57fbdc81d0e973a00692adfad3
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Tue Dec 15 13:34:50 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Dec 15 13:34:50 2020 +0100

    tools/xenstore: fire watches only when removing a specific node
    
    Instead of firing all watches for removing a subtree in one go, do so
    only when the related node is being removed.
    
    The watches for the top-most node being removed include all watches
    including that node, while watches for nodes below that are only fired
    if they are matching exactly. This avoids firing any watch more than
    once when removing a subtree.
    
    This is part of XSA-115.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
---
 tools/xenstore/xenstored_core.c  | 11 ++++++-----
 tools/xenstore/xenstored_watch.c | 13 ++++++++-----
 tools/xenstore/xenstored_watch.h |  4 ++--
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/tools/xenstore/xenstored_core.c b/tools/xenstore/xenstored_core.c
index c74413bda2..b39610c876 100644
--- a/tools/xenstore/xenstored_core.c
+++ b/tools/xenstore/xenstored_core.c
@@ -1111,8 +1111,8 @@ static void delete_child(struct connection *conn,
        corrupt(conn, "Can't find child '%s' in %s", childname, node->name);
 }
 
-static int delete_node(struct connection *conn, struct node *parent,
-                      struct node *node)
+static int delete_node(struct connection *conn, const void *ctx,
+                      struct node *parent, struct node *node)
 {
        char *name;
 
@@ -1124,7 +1124,7 @@ static int delete_node(struct connection *conn, struct 
node *parent,
                                       node->children);
                child = name ? read_node(conn, node, name) : NULL;
                if (child) {
-                       if (delete_node(conn, node, child))
+                       if (delete_node(conn, ctx, node, child))
                                return errno;
                } else {
                        trace("delete_node: Error deleting child '%s/%s'!\n",
@@ -1136,6 +1136,7 @@ static int delete_node(struct connection *conn, struct 
node *parent,
                talloc_free(name);
        }
 
+       fire_watches(conn, ctx, node->name, true);
        delete_node_single(conn, node);
        delete_child(conn, parent, basename(node->name));
        talloc_free(node);
@@ -1165,8 +1166,8 @@ static int _rm(struct connection *conn, const void *ctx, 
struct node *node,
         * This fine as we are single threaded and the next possible read will
         * be handled only after the node has been really removed.
         */
-       fire_watches(conn, ctx, name, true);
-       return delete_node(conn, parent, node);
+       fire_watches(conn, ctx, name, false);
+       return delete_node(conn, ctx, parent, node);
 }
 
 
diff --git a/tools/xenstore/xenstored_watch.c b/tools/xenstore/xenstored_watch.c
index f0bbfe7a6d..3836675459 100644
--- a/tools/xenstore/xenstored_watch.c
+++ b/tools/xenstore/xenstored_watch.c
@@ -122,7 +122,7 @@ static void add_event(struct connection *conn,
  * Temporary memory allocations are done with ctx.
  */
 void fire_watches(struct connection *conn, const void *ctx, const char *name,
-                 bool recurse)
+                 bool exact)
 {
        struct connection *i;
        struct watch *watch;
@@ -134,10 +134,13 @@ void fire_watches(struct connection *conn, const void 
*ctx, const char *name,
        /* Create an event for each watch. */
        list_for_each_entry(i, &connections, list) {
                list_for_each_entry(watch, &i->watches, list) {
-                       if (is_child(name, watch->node))
-                               add_event(i, ctx, watch, name);
-                       else if (recurse && is_child(watch->node, name))
-                               add_event(i, ctx, watch, watch->node);
+                       if (exact) {
+                               if (streq(name, watch->node))
+                                       add_event(i, ctx, watch, name);
+                       } else {
+                               if (is_child(name, watch->node))
+                                       add_event(i, ctx, watch, name);
+                       }
                }
        }
 }
diff --git a/tools/xenstore/xenstored_watch.h b/tools/xenstore/xenstored_watch.h
index 54d4ea7e0d..1b3c80d3dd 100644
--- a/tools/xenstore/xenstored_watch.h
+++ b/tools/xenstore/xenstored_watch.h
@@ -24,9 +24,9 @@
 int do_watch(struct connection *conn, struct buffered_data *in);
 int do_unwatch(struct connection *conn, struct buffered_data *in);
 
-/* Fire all watches: recurse means all the children are affected (ie. rm). */
+/* Fire all watches: !exact means all the children are affected (ie. rm). */
 void fire_watches(struct connection *conn, const void *tmp, const char *name,
-                 bool recurse);
+                 bool exact);
 
 void conn_delete_all_watches(struct connection *conn);
 
--
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