Bug 14541

Since 2.6.30-rc, I've been experiencing various issues relating to getcwd() returning ENOENT on NFS4 clients. This looks to be racy and is readily reproducible [1].

I bisected the issue [2] and confirm that manually backing out this patch against 2.6.32-rc5 restores correct race-free behaviour. The issue did not occur with 2.6.29, so is a regression.

To observe the change to user-level behaviour (after the reproducer commands):
# make clean
# strace -ffe getcwd make -n >list
[pid  3829] getcwd(0x7fffa269a380, 4096) = -1 ENOENT (No such file or directory)
make: getcwd: No such file or directory

-> this impacts userspace and causes varying levels of failure, which often are benign, but can break applications, eg it's impossible to build an Ubuntu/Debian kernel over NFS4 since 2.6.30-rc.

--- [1]

booting eg:
http://mira.sunsite.utk.edu/ubuntu-releases/karmic/ubuntu-9.10-desktop-amd64.iso

$ sudo bash
# apt-get install build-essential
# apt-get build-dep apt
# mount server:/ /mnt -tnfs4 && cd /mnt
# apt-get source apt
# cd apt-0.7.23.1ubuntu2
# ./configure && make
 -> "getcwd: No such file or directory" messages observed with cited
patch and not without

--- [2]

a65318bf3afc93ce49227e849d213799b072c5fd is first bad commit
commit a65318bf3afc93ce49227e849d213799b072c5fd
Author: Trond Myklebust <Trond.Myklebust@netapp.com>
Date:   Wed Mar 11 14:10:28 2009 -0400
NFSv4: Simplify some cache consistency post-op GETATTRs

To observe the change to user-level behaviour (after the reproducer commands):
# make clean
# strace -ffe getcwd make -n >list
[pid  3829] getcwd(0x7fffa269a380, 4096) = -1 ENOENT (No such file or directory)
make: getcwd: No such file or directory