[libvirt] [PATCH 3/3] nodedev: Work around the uevent race by hooking up virFileWaitForAccess
If we find ourselves in the situation that the 'add' uevent has been
fired earlier than the sysfs tree for a device, we'd better wait for the
attributes to be ready rather than discarding the device from our device
list forever.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1463285
Signed-off-by: Erik Skultety <eskultet(a)redhat.com>
---
src/node_device/node_device_udev.c | 48 +++++++++++++++++++++++++++++++++++++-
1 file changed, 47 insertions(+), 1 deletion(-)
diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index 174124a1b..4f9ca0c67 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -60,6 +60,43 @@ struct _udevPrivate {
};
+/**
+ * udevWaitForAttrs:
+ * @sys_path: node device base path
+ * @...: attributes to wait for, last attribute must be NULL
+ *
+ * Takes a list of attributes to wait for, waits until all of them are
+ * available, unless the max number of tries (10) has been reached.
+ *
+ * Returns 0 if all attributes became available, -1 on error.
+ */
+static int
+udevWaitForAttrs(const char *sys_path, ...)
+{
+ int ret = -1;
+ const char *attr = NULL;
+ char *attr_path = NULL;
+ va_list args;
+
+ va_start(args, sys_path);
+ while ((attr = va_arg(args, char *))) {
+ if (virAsprintf(&attr_path, "%s/%s", sys_path, attr) < 0)
+ goto cleanup;
+
+ if (virFileWaitForAccess(attr_path, 100, 10) < 0)
+ goto cleanup;
+
+ VIR_FREE(attr_path);
+ }
+
+ ret = 0;
+ cleanup:
+ va_end(args);
+ VIR_FREE(attr_path);
+ return ret;
+}
+
+
static bool
udevHasDeviceProperty(struct udev_device *dev,
const char *key)
@@ -1113,12 +1150,21 @@ udevProcessMediatedDevice(struct udev_device *dev,
{
int ret = -1;
const char *uuidstr = NULL;
+ const char *devpath = udev_device_get_syspath(dev);
int iommugrp = -1;
char *linkpath = NULL;
char *canonicalpath = NULL;
virNodeDevCapMdevPtr data = &def->caps->data.mdev;
- if (virAsprintf(&linkpath, "%s/mdev_type",
udev_device_get_syspath(dev)) < 0)
+ /* Because of a kernel uevent race, we might get the 'add' event prior to
+ * the sysfs tree being ready, so any attempt to access any sysfs attribute
+ * would result in ENOENT and us dropping the device, so let's work around
+ * it by waiting for the attributes to become available.
+ */
+ if (udevWaitForAttrs(devpath, "mdev_type", "iommu_group", NULL)
< 0)
+ goto cleanup;
+
+ if (virAsprintf(&linkpath, "%s/mdev_type", devpath) < 0)
goto cleanup;
if (virFileResolveLink(linkpath, &canonicalpath) < 0)
--
2.13.1