[libvirt PATCH] nodedev: switch to udev 'bind' events

[Jonathon Jongsma]

Rather than listening to 'add' udev events, listen for 'bind' events
instead. When we get an 'add' event, the sysfs tree for the device is
often not ready yet. In that case we sleep in a loop until the sysfs
tree appears, or give up after a timeout.

udev added the 'bind' event to give userspace a signal that indicated
when driver-specific attributes were available to be used. In other
words, the sysfs tree *should* be ready and usable at this point.
But just to be safe, we'll leave the wait loop in the code to handle
corner cases, with the hope that it'll never be used.

The udev 'bind' event was added in kernel 4.14 and the oldest platform
we support has kernel 4.18, so it should be safe to make this change.

Previous discussion on the mailing list:
https://listman.redhat.com/archives/libvir-list/2022-August/233933.html

Signed-off-by: Jonathon Jongsma <jjongsma at redhat.com>
---
 src/node_device/node_device_udev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index 07c10f0d88..781a8b32a6 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -1759,7 +1759,7 @@ udevHandleOneDevice(struct udev_device *device)
 
     VIR_DEBUG("udev action: '%s': %s", action, udev_device_get_syspath(device));
 
-    if (STREQ(action, "add") || STREQ(action, "change"))
+    if (STREQ(action, "bind") || STREQ(action, "change"))
         return udevAddOneDevice(device);
 
     if (STREQ(action, "remove"))
-- 
2.37.2