[linux-lvm] temporary uninterruptible sleep on thin pool under massive write

[Alexey]

Hello.

I have a problem with LVM thin pool. I have several VG in my 
installation, each VG contains one TP, in each TP there is several thin 
LV. Each VG have only one PV created on SSD INTEL SSDSC2BB48 D201.

For reproduce the bug I start dd: dd if=/dev/zero of=/dev/vg3/testdd 
bs=4M count=1000
The dd process dealing its job without any problem, but if we see "ps", 
the state of the dd process will be "D+". During "D+" state dd works 
fine and write data to disk, BUT any other attempts  to use the same VG 
as dd for read or write operations is impossible until dd will not stop.
Any other VG works fine during this problem.

I tried to run dd with ionice: ionice -c idle dd if=/dev/zero 
of=/dev/vg3/testdd bs=4M count=1000. It didn't help.

# lvm version
   LVM version:     2.02.106(2) (2014-04-10)
   Library version: 1.02.85 (2014-04-10)
   Driver version:  4.27.0

I'll try Linux 3.10.61 from kernel.org and 3.10 from CentOS (RHEL_MAJOR 
= 7, RHEL_MINOR = 0, RHEL_RELEASE = 123.9.3).


Regards,
Alexey Mochkin