Patch to add support for advertising FULLSYNC to Mac OSX Clients

[Kevin Anderson]

Hi Ralph,

That works for me. :) Let me know if there is anything else I can help with.

-Kevin

On Tue, Feb 21, 2017 at 12:31 PM, Ralph Böhme <slow at samba.org> wrote:
> Hi Kevin,
>
> On Sat, Feb 18, 2017 at 06:32:00PM -0500, Kevin Anderson wrote:
>> > > > I've also added code that ensures all prerequisite Samba options are
>> > > > set on the fly when a Time Machine enabled share is connected.
>> > > >
>> > > > Now, secondly, the interesting part: have you ever tested if the TM
>> > > > disk image filesystem survives network disconnects and/or hard server
>> > > > power offs ?
>> > > >
>> > >
>> > > I have been running the provided patch set for the past month and have not
>> > > noticed any issues. In that time I have restarted the networking interfaces
>> > > on the server I am using while backups are running without any issues being
>> > > reported as well as being able to restore from the same backup. With that
>> > > being said I have not tested a hard poweroff of the server as it is backed
>> > > by an UPS. I will try to test this case and report back.
>> >
>> > did you run into any issues?
>> >
>>
>> So far I have not run in to any issues even doing a hard power off a
>> couple of times.
>
> ok.
>
>> > > Also based one this email thread, Samba FLUSH operations are
>> > > asynchronous by default:
>> > >
>> > > https://lists.samba.org/archive/samba/2008-September/143627.html
>> >
>> > yes, they are asynchronous *and* they're disabled by default (strict sync =
>> > no), that's why we'ge going to enable it at runtime if fruit:time machine=yes.
>>
>> OK.
>>
>> >
>> > > The asynchronous writes make me curious if this might be leading to
>> > > some of the corruption edge cases as well as the case above.
>> >
>> > Hm, I guess the time window is small where we responsed to the flush request
>> > while the fsync is still being done in a worker thread, but it's there, so yes,
>> > this could be possible.
>> >
>> > > Is it possible to force a fsync() from the VFS layer? Could we add a handler
>> > > for SMB2 FLUSH commands that check for a Reserved1 Field set to 0xFFFF and
>> > > force an fsync()?
>> >
>> > Yes, we probably want to parse the Reserved1 field in the SMB2 frontend and pass
>> > it down to the SMB2 flush request handler. Depending on the setting we could the
>> > switch between callinc async flush() or sync.
>>
>> OK. I will look to adding that to the provided patch but it may take
>> some time as I understand some other parts of the code base. I think
>> that would provide the necessary balance between data consistency and
>> performance.
>
> I can do this part, you can then do the testing. :)
>
> Cheerio!
> -slow