Re: nfs stale filehandle issues with 2.6.10-rc1 in-kernel server

["Jeff V. Merkey" <jmerkey@drdos.com>]

Jeff V. Merkey wrote:

> Trond Myklebust wrote:
>
>>
>>>> Connect 2.4.18 and 2.6.9 with NFS 3 enabled.  I am seeing problems 
>>>> connecting and file size mismatches.  I also see errors with zero
>>>> length files (host side) that get opened and populated with data
>>>> and the remote side is unable to read them -- keeps seeing them as 
>>>> zero length.      
>>>
>>
>> That's entirely expected. NFS has always been forced to use a polling
>> model for attribute cache consistency. "man 5 nfs" and read all about
>> the "actimeo" mount options that control this behaviour.
>>
>> Cheers,
>>  Trond
>>
>>  
>>
> Trond,
>
> Thanks for the update.  I noticed from another post on this thread 
> that the problems with
> /etc/exports are being addressed.  This was the other problem I was 
> seeing but it appears
> to be getting fixed.
>
> Jeff
>
>
>
Trond,

While you are running down this problem, I've located another odd 
behavior you
may (or may not) chose to address.  In my dsfs file system, I use sector 
runs (large ones)
that can sometimes return odd sizes during running down a file for 
reading. 

i.e.  I can return 4096,4096,4096,512,1024,4096,4096 block sizes on size 
returns
from vfs_read() for 512 or 4096 block requests when the file is read 
sequentially. 
Under NTFS and other OS architectures, unless the final read attempt 
returns 0 size
denoting end of file, this seems to be allowed.  I noticed that all of 
the linux code with
the exception of NFS also handles this situation quite nicely.  NFS does 
not.  I have
noted that if NFS receives a read size smaller than the requested block, 
it always assumes
end of file and terminates the next read.  I hace modified dsfs to 
always return
block sizes in a uniform manner so NFS will work properly, even though 
the rest
of the Linux apps work just fine without assuming the end of file has 
been reached. 

I personally think this is a broken behavior, but perhaps it's in line 
with some NFS
spec somewhere.  I have coded around it, but thout I would mention it to
you.

Jeff