[PATCH 6/9] libxl: check backend state before setting it to "closing"

[Roger Pau Monne <roger.pau@citrix.com>]

Check backend state before unconditionally setting it to "closing"
(5), since it might already be in "closed" (6).

Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
---
 tools/libxl/libxl_device.c |   53 +++++++++++++++++++++++++++++++------------
 1 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 8ae2bb5..18002a0 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -681,10 +681,11 @@ void libxl__initiate_device_remove(libxl__egc *egc,
                                    libxl__ao_device *aodev)
 {
     STATE_AO_GC(aodev->ao);
-    libxl_ctx *ctx = libxl__gc_owner(gc);
     xs_transaction_t t = 0;
     char *be_path = libxl__device_backend_path(gc, aodev->dev);
     char *state_path = libxl__sprintf(gc, "%s/state", be_path);
+    char *online_path = GCSPRINTF("%s/online", be_path);
+    const char *state;
     int rc = 0;
 
     /* We init this here because we might call device_hotplug_done
@@ -701,23 +702,44 @@ void libxl__initiate_device_remove(libxl__egc *egc,
         goto out;
     }
 
-retry_transaction:
-    t = xs_transaction_start(ctx->xsh);
-    if (aodev->force)
-        libxl__xs_path_cleanup(gc, t,
-                               libxl__device_frontend_path(gc, aodev->dev));
-    xs_write(ctx->xsh, t, libxl__sprintf(gc, "%s/online", be_path), "0", strlen("0"));
-    xs_write(ctx->xsh, t, state_path, "5", strlen("5"));
-    if (!xs_transaction_end(ctx->xsh, t, 0)) {
-        if (errno == EAGAIN)
-            goto retry_transaction;
-        else {
-            rc = ERROR_FAIL;
+    for (;;) {
+        rc = libxl__xs_transaction_start(gc, &t);
+        if (rc) {
+            LOG(ERROR, "unable to start transaction");
+            goto out;
+        }
+
+        rc = libxl__xs_read_checked(gc, t, state_path, &state);
+        if (rc) {
+            LOG(ERROR, "unable to read device state from path %s", state_path);
             goto out;
         }
+
+        if (aodev->force)
+            libxl__xs_path_cleanup(gc, t,
+                                   libxl__device_frontend_path(gc, aodev->dev));
+
+        /*
+         * Check if device is already in "closed" state, in which case
+         * it should not be changed.
+         */
+        if (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, "5");
+            if (rc) {
+                LOG(ERROR, "unable to write to xenstore path %s", state_path);
+                goto out;
+            }
+        }
+
+        rc = libxl__xs_transaction_commit(gc, &t);
+        if (!rc) break;
+        if (rc < 0) goto out;
     }
-    /* mark transaction as ended, to prevent double closing it on out_ok */
-    t = 0;
 
     libxl__device_destroy_tapdisk(gc, be_path);
 
@@ -733,6 +755,7 @@ retry_transaction:
     return;
 
 out:
+    libxl__xs_transaction_abort(gc, &t);
     aodev->rc = rc;
     device_hotplug_done(egc, aodev);
     return;
-- 
1.7.7.5 (Apple Git-26)