On Mon, Jun 16, 2008 at 8:39 AM, Peter Staubach <staubach@xxxxxxxxxx> wrote:
> NeilBrown wrote:
>>
>> OCFS2 can return -ERESTARTSYS from write requests (and possibly
>> elsewhere) if there is a signal pending.
>>
>> If nfsd is shutdown (by sending a signal to each thread) while there
>> is still an IO load from the client, each thread could handle one last
>> request with a signal pending. This can result in -ERESTARTSYS
>> which is not understood by nfserrno() and so is reflected back to
>> the client as nfserr_io aka -EIO. This is wrong.
>>
>> Instead, interpret ERESTARTSYS to mean "don't send a reply".
>> The client will resend and - if the server is restarted - the write will
>> (hopefully) be successful and everyone will be happy.
>>
>>
>
> Why not handle -ERESTARTSYS in the same fashion as -ETIMEDOUT, ie.
> leading to a EJUKEBOX sort of error being returned if possible?
>
> Simply not returning is a bad thing to do for anything other than
> NFSv2. It is especially bad for NFSv4.
Actually, the NFSv4 spec *requires* the server to reply to every request.
Not replying means an NFSv4 client connected via NFSv4 will have to
disconnect and retransmit. That should be avoided if at all possible.
I think an error reply is much better than no reply in nearly every
case. NFS3ERR_JUKEBOX/NFS4ERR_DELAY is an interesting idea, but
something else again will probably be required for v4.1 with sessions.
>> Signed-off-by: Neil Brown <neilb@xxxxxxx>
>>
>> ### Diffstat output
>> ./fs/nfsd/nfsproc.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> ----
>> Funny how the shortest patches sometimes have the longest
>> descriptions.
>>
>> The symptom that I narrowed down to this was:
>> copy a large file via NFS to an OCFS2 filesystem, and restart
>> the nfs server during the copy.
>> The 'cp' might get an -EIO, and the file will be corrupted -
>> presumably holes in the middle were writes appeared to fail.
>>
>> diff .prev/fs/nfsd/nfsproc.c ./fs/nfsd/nfsproc.c
>> --- .prev/fs/nfsd/nfsproc.c 2008-06-13 21:31:53.000000000 +1000
>> +++ ./fs/nfsd/nfsproc.c 2008-06-13 21:31:57.000000000 +1000
>> @@ -614,6 +614,7 @@ nfserrno (int errno)
>> #endif
>> { nfserr_stale, -ESTALE },
>> { nfserr_jukebox, -ETIMEDOUT },
>> + { nfserr_dropit, -ERESTARTSYS },
>> { nfserr_dropit, -EAGAIN },
>> { nfserr_dropit, -ENOMEM },
>> { nfserr_badname, -ESRCH },
>>
>> ### Diffstat output
>> ./fs/nfsd/nfsproc.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff .prev/fs/nfsd/nfsproc.c ./fs/nfsd/nfsproc.c
>> --- .prev/fs/nfsd/nfsproc.c 2008-06-13 21:31:53.000000000 +1000
>> +++ ./fs/nfsd/nfsproc.c 2008-06-13 21:31:57.000000000 +1000
>> @@ -614,6 +614,7 @@ nfserrno (int errno)
>> #endif
>> { nfserr_stale, -ESTALE },
>> { nfserr_jukebox, -ETIMEDOUT },
>> + { nfserr_dropit, -ERESTARTSYS },
>> { nfserr_dropit, -EAGAIN },
>> { nfserr_dropit, -ENOMEM },
>> { nfserr_badname, -ESRCH },
>> --
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>
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which wants to have more food and not more cars. First food, then if
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has to come first.
-- Evo Morales
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