How does the client manage NFS3ERR_NOSPC ?

How does the client manage NFS3ERR_NOSPC ?

[DENIEL Philippe]

Hi List,

I ran a stupid test (using the kernel's knfsd) : I filled up completely 
a filesystem with a few big file. When it was 100% full (no free block 
at all), I ran a dd on it.
The dd said it could write 793 blocks of size 1mb  and failed on IO 
error. At the end, I could see an empty file in the NFS exported tree.
Question is :
    - why did I get EIO and not ENOSPC ?
    - why did dd say "hey, I could write 793 blocks" when it wrote 
nothing (and could not write anything).
Do you have an idea on that ?

    Regards

       Philippe

Re: How does the client manage NFS3ERR_NOSPC ?

[Myklebust, Trond]

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Re: How does the client manage NFS3ERR_NOSPC ?

[Malahal Naineni]

Myklebust, Trond [Trond.Myklebust@netapp.com] wrote:
> On Mon, 2012-03-05 at 18:16 +0100, DENIEL Philippe wrote:
> > Hi List,
> > 
> > I ran a stupid test (using the kernel's knfsd) : I filled up completely 
> > a filesystem with a few big file. When it was 100% full (no free block 
> > at all), I ran a dd on it.
> > The dd said it could write 793 blocks of size 1mb  and failed on IO 
> > error. At the end, I could see an empty file in the NFS exported tree.
> > Question is :
> >     - why did I get EIO and not ENOSPC ?
> 
> Did the server actually return NFS3ERR_NOSPC, or did it return something
> else? If the server returns NFS3ERR_NOSPC, then I'd expect the client to
> translate that as ENOSPC.

AFAIR, the server returns ENOSPC but the Linux client has a bug under
certain cases that returns it as EIO. Filed a bug and Neil sent a patch
but I have not tested it yet.

I tried with various versions and they gave some differing results. I
think in one case fsync() got ENOSPC but close() got EIO (or the other
way around?)

Regards, Malahal.
PS: Easy way to reproduce the problem, just run the following:
dd if=/dev/zero of=./testfile conv=fdatasync