BUG #13515: Much higher disk writes after postgres upgrade 9.4.3->9.4.4

The following bug has been logged on the website:

Bug reference: 13515
Logged by: Sushant Sinha
Email address: sushant(at)indiankanoon(dot)com
PostgreSQL version: 9.4.4
Operating system: Linux
Description:

After upgrade from postgres 9.4.3 to 9.4.4 I am seeing constant disk writes
of 4-8MB/s in the background in production. I verified it using iotop and
vmstat. iotop shows "Total Disk Write" to be minuscule (like 10-100Kbps). It
is affecting runtime performance. I never noticed this issue with postgres
9.4.3.

I increased the shared buffers from 128MB to 1GB and still didn't see any
benefit.

The website (http://indiankanoon.org) mostly uses text search with gin index
and some logging of click through data. The main database is replicated
using "streaming asynchronous replication".

I am going to downgrade it to 9.4.3 to see if the upgrade was the real
problem. But just wanted to check if anyone else noticed it.