Re: [PATCH 4/4] xfs: fallback to buffered I/O for direct I/O when stable writes are required

Qu Wenruo
2025-10-30T06:37:55Z

在 2025/10/30 16:28, Christoph Hellwig 写道:
[...]
>> It will be much straightforward if there is some flag allowing us to return
>> error directly if true zero-copy direct IO can not be executed.
>
> I don't really understand this part.

I mean some open flag like O_DIRECT_NO_FALLBACK, then we can directly
reutrn -ENOBLK without falling back to buffered IO (and no need to
bother the warning of falling back).

This will provide the most accurate, true zero-copy for those programs
that really require zero-copy.

And we won't need to bother falling back to buffered IO, it will be
something for the user space to bother.

Thanks,
Qu