RHEL7 / RHEL6.7: Slow NFS operation (ls -l) with NFSv3 mount on RHEL6 kernel-2.6.32-573.el6 and above due to directory being modified while listing is in progress

Issue

• After updating to the latest RHEL6 kernel to kernel-2.6.32-573.18.1.el6.x86_64 we experience slow response to "ls" command to NFS mounted filesystem:

root@client:/root # time ls -l  /mnt/nfs
^C

real    7m27.137s
user    0m0.164s
sys     0m12.179s

• With kernel 2.6.32-504.23.4.el6.x86_64 the same operation completes within 30 seconds:

root@client:/root # uname -a
Linux client 2.6.32-504.23.4.el6.x86_64 #1 SMP Fri May 29 10:16:43 EDT 2015 x86_64 x86_64 x86_64 GNU/Linux
root@client:/root #  time ls -l /mnt/nfs

….
real    0m30.151s
user    0m0.922s
sys     0m1.574s

• The directory contains about 100.000 files and is served from an AIX6.1 server. NFS statistics shows a large amount of READDIRPLUS operations.