[Xen-changelog] [xen stable-4.6] libxl: fix devd removal path

[patchbot@xxxxxxx]

commit fe6a5ad304dde6d724e763518296a40aa2ff484e
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Wed Sep 23 12:06:55 2015 +0200
Commit:     Ian Campbell <ian.campbell@xxxxxxxxxx>
CommitDate: Thu Sep 24 11:43:31 2015 +0100

    libxl: fix devd removal path

    The current flow of the devd helper (in charge of launching hotplug scripts
    inside of driver domains) is to wait for the device backend to switch to
    state 6  (XenbusStateClosed) and then remove it. This is not correct, since
    a domain can reconnect it's PV devices as many times as it wants.

    In order to fix this, introduce the following logic: the control domain will
    set the "online" backend node to 0 when it wants the driver domain to
    disconnect the device, so now the condition applied in devd is that "state"
    must be 6 and "online" 0 in order to proceed with the disconnection.

    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reported-by: Alex Velazquez <alex.j.velazquez@xxxxxxxxx>
    Cc: Alex Velazquez <alex.j.velazquez@xxxxxxxxx>
    Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
    Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
    Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
    (cherry picked from commit 5c9a00c57172182652c432e80cc278bebc044dc4)
---
 tools/libxl/libxl.c        |   32 ++++++++++++++++++--------------
 tools/libxl/libxl_device.c |    9 ++++-----
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 4d27891..d38d0c7 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -4421,32 +4421,36 @@ static void backend_watch_callback(libxl__egc *egc, 
libxl__ev_xswatch *watch,
     libxl__ao *nested_ao = libxl__nested_ao_create(ddomain->ao);
     STATE_AO_GC(nested_ao);
     char *p, *path;
-    const char *sstate;
-    int state, rc, num_devs;
+    const char *sstate, *sonline;
+    int state, online, rc, num_devs;
     libxl__device *dev = NULL;
     libxl__ddomain_device *ddev = NULL;
     libxl__ddomain_guest *dguest = NULL;
     bool free_ao = false;

-    /* Check if event_path ends with "state" and truncate it */
-    if (strlen(event_path) < strlen("state"))
-        goto skip;
-
+    /* Check if event_path ends with "state" or "online" and truncate it. */
     path = libxl__strdup(gc, event_path);
-    p = path + strlen(path) - strlen("state") - 1;
-    if (*p != '/')
+    p = strrchr(path, '/');
+    if (p == NULL)
         goto skip;
-    *p = '\0';
-    p++;
-    if (strcmp(p, "state") != 0)
+    if (strcmp(p, "/state") != 0 && strcmp(p, "/online") != 0)
         goto skip;
+    /* Truncate the string so it points to the backend directory. */
+    *p = '\0';

-    /* Check if the state is 1 (XenbusStateInitialising) or greater */
-    rc = libxl__xs_read_checked(gc, XBT_NULL, event_path, &sstate);
+    /* Fetch the value of the state and online nodes. */
+    rc = libxl__xs_read_checked(gc, XBT_NULL, GCSPRINTF("%s/state", path),
+                                &sstate);
     if (rc || !sstate)
         goto skip;
     state = atoi(sstate);

+    rc = libxl__xs_read_checked(gc, XBT_NULL, GCSPRINTF("%s/online", path),
+                                &sonline);
+    if (rc || !sonline)
+        goto skip;
+    online = atoi(sonline);
+
     dev = libxl__zalloc(NOGC, sizeof(*dev));
     rc = libxl__parse_backend_path(gc, path, dev);
     if (rc)
@@ -4488,7 +4492,7 @@ static void backend_watch_callback(libxl__egc *egc, 
libxl__ev_xswatch *watch,
         rc = add_device(egc, nested_ao, dguest, ddev);
         if (rc > 0)
             free_ao = true;
-    } else if (state == XenbusStateClosed) {
+    } else if (state == XenbusStateClosed && online == 0) {
         /*
          * Removal of an active device, remove it from the list and
          * free it's data structures if they are no longer needed.
diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index bee5ed5..85a3662 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -837,16 +837,15 @@ void libxl__initiate_device_remove(libxl__egc *egc,
             goto out;
         }

+        rc = libxl__xs_write_checked(gc, t, online_path, "0");
+        if (rc)
+            goto out;
+
         /*
          * Check if device is already in "closed" state, in which case
          * it should not be changed.
          */
          if (state && atoi(state) != XenbusStateClosed) {
-            rc = libxl__xs_write_checked(gc, t, online_path, "0");
-            if (rc) {
-                LOG(ERROR, "unable to write to xenstore path %s", online_path);
-                goto out;
-            }
             rc = libxl__xs_write_checked(gc, t, state_path, GCSPRINTF("%d", 
XenbusStateClosing));
             if (rc) {
                 LOG(ERROR, "unable to write to xenstore path %s", state_path);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog