From a9567e09ef43ab01f7beb4c1d1c2ff4aef13fca2 Mon Sep 17 00:00:00 2001
From: Chris Lalancette <clalance@redhat.com>
Date: Fri, 28 Nov 2008 07:50:20 +0000
Subject: [PATCH] Instead of relying solely on polling for /dev devices to
 appear in libvirt, we really should be synchronizing against udev.  This is
 generally done by a call to udevsettle, which is exactly what this patch
 implements for the storage backends that are likely to create new /dev nodes.
  I believe I've read that even after udevsettle, you are not guaranteed that
 devices are all the way created, so we still need the polling in the rest of
 the sources, but this should give us a much better chance of things existing
 as we expect.

Signed-off-by: Chris Lalancette <clalance@redhat.com>
---
 configure.in                  |  6 ++++++
 src/storage_backend.c         | 21 +++++++++++++++++++++
 src/storage_backend.h         |  2 ++
 src/storage_backend_disk.c    |  2 ++
 src/storage_backend_iscsi.c   |  2 ++
 src/storage_backend_logical.c |  2 ++
 6 files changed, 35 insertions(+)

diff --git a/configure.in b/configure.in
index 30929ee618..5359433a1f 100644
--- a/configure.in
+++ b/configure.in
@@ -115,11 +115,17 @@ AC_PATH_PROG([DNSMASQ], [dnsmasq], [dnsmasq],
 	[/sbin:/usr/sbin:/usr/local/sbin:$PATH])
 AC_PATH_PROG([BRCTL], [brctl], [brctl],
 	[/sbin:/usr/sbin:/usr/local/sbin:$PATH])
+AC_PATH_PROG([UDEVADM], [udevadm], [],
+	[/sbin:/usr/sbin:/usr/local/sbin:$PATH])
 
 AC_DEFINE_UNQUOTED([DNSMASQ],["$DNSMASQ"],
         [Location or name of the dnsmasq program])
 AC_DEFINE_UNQUOTED([BRCTL],["$BRCTL"],
         [Location or name of the brctl program (see bridge-utils)])
+if test -n "$UDEVADM"; then
+  AC_DEFINE_UNQUOTED([UDEVADM],["$UDEVADM"],
+        [Location or name of the udevadm program])
+fi
 
 dnl Specific dir for HTML output ?
 AC_ARG_WITH([html-dir], [AC_HELP_STRING([--with-html-dir=path],
diff --git a/src/storage_backend.c b/src/storage_backend.c
index 9266e5cdc6..6b4fa818cb 100644
--- a/src/storage_backend.c
+++ b/src/storage_backend.c
@@ -270,6 +270,27 @@ virStorageBackendUpdateVolInfoFD(virConnectPtr conn,
     return 0;
 }
 
+#ifdef UDEVADM
+void virStorageBackendWaitForDevices(virConnectPtr conn)
+{
+    const char *const settleprog[] = { UDEVADM, "settle", NULL };
+    int exitstatus;
+
+    if (access(UDEVADM, X_OK) != 0)
+        return;
+
+    /*
+     * NOTE: we ignore errors here; this is just to make sure that any device
+     * nodes that are being created finish before we try to scan them.
+     * If this fails for any reason, we still have the backup of polling for
+     * 5 seconds for device nodes.
+     */
+    virRun(conn, settleprog, &exitstatus);
+}
+#else
+void virStorageBackendWaitForDevices(virConnectPtr conn ATTRIBUTE_UNUSED) {}
+#endif
+
 /*
  * Given a volume path directly in /dev/XXX, iterate over the
  * entries in the directory pool->def->target.path and find the
diff --git a/src/storage_backend.h b/src/storage_backend.h
index 7904d9d061..06f6979ad9 100644
--- a/src/storage_backend.h
+++ b/src/storage_backend.h
@@ -69,6 +69,8 @@ int virStorageBackendUpdateVolInfoFD(virConnectPtr conn,
                                      int fd,
                                      int withCapacity);
 
+void virStorageBackendWaitForDevices(virConnectPtr conn);
+
 char *virStorageBackendStablePath(virConnectPtr conn,
                                   virStoragePoolObjPtr pool,
                                   const char *devpath);
diff --git a/src/storage_backend_disk.c b/src/storage_backend_disk.c
index 458e30773c..127e02c4a3 100644
--- a/src/storage_backend_disk.c
+++ b/src/storage_backend_disk.c
@@ -262,6 +262,8 @@ virStorageBackendDiskRefreshPool(virConnectPtr conn,
     VIR_FREE(pool->def->source.devices[0].freeExtents);
     pool->def->source.devices[0].nfreeExtent = 0;
 
+    virStorageBackendWaitForDevices(conn);
+
     return virStorageBackendDiskReadPartitions(conn, pool, NULL);
 }
 
diff --git a/src/storage_backend_iscsi.c b/src/storage_backend_iscsi.c
index 54a6409e0a..b347fa9308 100644
--- a/src/storage_backend_iscsi.c
+++ b/src/storage_backend_iscsi.c
@@ -603,6 +603,8 @@ virStorageBackendISCSIRefreshPool(virConnectPtr conn,
 
     pool->def->allocation = pool->def->capacity = pool->def->available = 0;
 
+    virStorageBackendWaitForDevices(conn);
+
     if ((session = virStorageBackendISCSISession(conn, pool)) == NULL)
         goto cleanup;
     if (virStorageBackendISCSIRescanLUNs(conn, pool, session) < 0)
diff --git a/src/storage_backend_logical.c b/src/storage_backend_logical.c
index ee8e8f84d2..a358c43206 100644
--- a/src/storage_backend_logical.c
+++ b/src/storage_backend_logical.c
@@ -470,6 +470,8 @@ virStorageBackendLogicalRefreshPool(virConnectPtr conn,
     };
     int exitstatus;
 
+    virStorageBackendWaitForDevices(conn);
+
     /* Get list of all logical volumes */
     if (virStorageBackendLogicalFindLVs(conn, pool, NULL) < 0) {
         virStoragePoolObjClearVols(pool);