[lvm-devel] lvcreate hangs forever and udev work timeout

[Eric Ren]

Hi,

The reason is found out, as you've predicted.

> is it because of slow read operation (i.e. some raid arrays are known to
> wake-up slowly)

The udev worker is blocked until timeout before killed, cause the
"blkid" in /usr/lib/udev/rules.d/13-dm-disk.rules is too slow because
of high IO load on the thin pool.

After remove this rule:

IMPORT{builtin}="blkid"

for testing, the problem cannot be reproduced any more.

But, we tried to increate udevd timeout to 5 min, the problem still
happens; with 10 min timeout, can workaround this problem.

>From my understanding, the blkid will only read the fs superblock, why
it takes so long for a small IO to finish, even under high IO load?

Regards,
Eric