[Samba] What's the difference between source3 and source4 in samba? How to use an asynchronous file system?

[Volker Lendecke]

On Mon, Jul 11, 2016 at 01:06:53PM +0000, withlog at yahoo.com wrote:
>  Hi, list,     I recently begin to study samba source code. Now I
> have some questions to ask. Can you give me some help?     The first
> question is what the relationship between samba versions(such as
> 3.x.x , 4.x.x) and samba3/samba4. In samba source code, I find two
> directories, souce3 and soure4. Do they mean  samba3 and samba4? 
> Actually, almost all docs in samba are about samba3, where to find
> docs about samba4?     The second question is how to use an
> asynchronous file system interface in samba? Actually we develop a
> new file system. But in our system, synchronous interfaces worked
> poorly, so we begin to use  asynchronous  interfaces. I only find
> this case in source4. Is that right?  Someone said source4 will be
> deprecated. Is this true?

source4/ntvfs has not seen any updates for a while, most SMB protocol and
file server development happened in source3. If you want to revive that,
feel free, but you'll be pretty much on your own.

What exactly are your interfaces that you are async instead of sync?
The source3/smbd/smb2* file at its core is already pretty much async,
however many of our core routines are not. If have specially severe
pain points for bad sync API behaviour, that might be a reason for
making it more asynchronous. BTW, pread/pwrite are already async.

Regards, Volker