On 2023/3/28 21:01, Ming Lei wrote:

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So re-using splice for this purpose is still bad not mention splice
can't support writeable spliced page.

Wiring device io buffer with context registered buffer table looks like
another approach, however:

1) two uring command OPs for registering/unregistering this buffer in io fast
path has to be added since only userspace can know when buffer(reference)
isn't needed

Yes, that's a good point. Registration replaces fuse master cmd, so it's
one extra request for unregister, which might be fine.

Unfortunately I don't think this way is good, the problem is that buffer
only has physical pages, and doesn't have userspace mapping, so why bother
to export it to userspace?

As I replied to Ziyang, the current fused command can be extended to
this way easily, but I don't know why we need to use the buffer registration,
given userspace can't read/write the buffer, and fused command can cover
it just fine.

Hi Ming, I have replied to you in another email.