Re: [PATCH] fcntl.2, read.2, write.2: document "Lost locks" as cause for EIO.

NeilBrown
2017-12-19T20:30:06Z

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On Tue, Dec 19 2017, Michael Kerrisk (man-pages) wrote:

> On 12/18/2017 10:45 PM, NeilBrown wrote:
>> On Mon, Dec 18 2017, Michael Kerrisk (man-pages) wrote:
>>
>>> Hello Neil
>>>
>>> There's a piece of your patch I don't understand. Please see below.
>>>
>>> On 12/13/2017 05:19 AM, NeilBrown wrote:
>>>>
>>>> If an advisory lock is lost, then read/write requests on any
>>>> affected file descriptor can return EIO - for NFSv4 at least.
>>>>
>>>> Signed-off-by: NeilBrown <neilb@suse.com>
>>>> ---
>>>> man2/fcntl.2 | 24 ++++++++++++++++++++++++
>>>> man2/read.2 | 9 +++++++++
>>>> man2/write.2 | 9 +++++++++
>>>> 3 files changed, 42 insertions(+)
>>>>
>>>> diff --git a/man2/fcntl.2 b/man2/fcntl.2
>>>> index 67642384154c..6e6e26f66aa0 100644
>>>> --- a/man2/fcntl.2
>>>> +++ b/man2/fcntl.2
>>>> @@ -669,6 +669,30 @@ and
>>>> Mandatory locking is not specified by POSIX.
>>>> Some other systems also support mandatory locking,
>>>> although the details of how to enable it vary across systems.
>>>> +.SS Lost locks
>>>> +When an advisory lock is obtained on a networked filesystem such as
>>>> +NFS it is possible that the lock might get lost.
>>>> +This may happen due to administrative action on the server, or due to a
>>>> +network partition which lasts long enough for the server to assume
>>>
>>> What does "network partition which lasts long enough" mean?
>>> I think this perhaps needs to be clarified a little. At least,
>>> I don't understand it.
>>
>> "network partition" is a term using the NFS RFCs for any situation that
>> that results in the server and client not being able to communicate
>> (that are partitioned, one from the other? There is partition (wall)
>> between them? They are in separate partitions?).
>> I can see how the meaning might not be obvious if you hadn't come across
>> it before.
>>
>> If we change "network partition" to "loss of connectivity", would that
>> make it clear. Is "loss of network connectivity with the server" too
>> verbose?
>
> Thanks, Neil. I've applied your patch and added the words "loss of network
> connectivity with the server".

Looks good. Thanks!

NeilBrown