[Samba] Direct I/O

Ralph Boehme slow at samba.org
Mon Jan 24 18:21:05 UTC 2022

On 1/24/22 18:39, Jeremy Allison via samba wrote:
> No, we don't currently use O_DIRECT on Linux.
> It doesn't match to SMB2+ semantics.

I think it does (SMB2_WRITEFLAG_WRITE_UNBUFFERED), but we don't yet 
implement it correctly. We check the flag and basically skip an fsync() 
done in some cases, but we don't pass it to the OS. I guess the problem 
is that in SMB the unbuffered is requested per *write* whereas we can 
only request unbuffered IO per *handle* with O_DIRECT. But I may be 
missing something.


Ralph Boehme, Samba Team                 https://samba.org/
SerNet Samba Team Lead      https://sernet.de/en/team-samba
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