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How does the client manage NFS3ERR_NOSPC ?

DISCUSSION DENIEL Philippe 3 participants 3 messages Mar 5, 2012

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DENIEL Philippe

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#0 lore raw

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

#1 lore raw

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#2 lore raw
Quoted 11 lines · Myklebust, Trond [[email protected]] wrote:
Quoted 9 lines · 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 ?

Quoted 3 lines

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