Re: New file doesn't show up if cached as missing

[Trond Myklebust <trond.myklebust@fys.uio.no>]

On Fri, 2009-05-29 at 10:52 -0700, Simon Kirby wrote:
> Hello!
> 
> On Linux 2.6.28.10 server and client, with NFSv3 or NFSv4, I can
> fairly easily reproduce a case where creating a file (open,write,close)
> and then attempting to open it on another client mounting the same server
> returns ENOENT.  If I run "ls" before I try to cat it, it works.
> 
> To reproduce:
> 
> ssh root@lps01 'rm -f /shared/ssl/test; stat /shared/ssl/test'; \
> ssh root@lps02 'echo hi > /shared/ssl/test'; \
> ssh root@lps01 'cat /shared/ssl/test'
> 
> The original stat (or cat or open) is important as it seems to cache that
> the file does not exist.  I can then even log in and poke around:
> 
> lps01:~# cd /shared
> lps01:/shared# cat test
> cat: test: No such file or directory
> lps01:/shared# stat test
> stat: cannot stat `test': No such file or directory
> lps01:/shared# ls test
> ls: test: No such file or directory
> lps01:/shared# ls
> <files including "test">
> lps01lsh:/shared# cat test
> hi
> 
> Is this expected behaviour?  The file system is mounted on both clients
> with: rw,hard,intr,...,acdirmin=0,acdirmax=0,acregmin=0,acregmax=0,noac
> 
> (eg: we can't find a way to make it not happen.)

That is most likely to be a consequence of poor mtime resolution on the
server (i.e. the directory mtime failing to change because the file
creation occurred within < 1 second of the 'rm'), combined with negative
lookup caching.

Try using the '-olookupcache=positive' or '-olookupcache=none' mount
options (requires a relatively recent version of nfs-utils).

Trond