On Fri, May 05, 2023 at 09:01:58AM +0100, John Garry wrote:

On 04/05/2023 23:40, Dave Chinner wrote:

Hi Dave,

quoted

quoted

No, not yet. Is it normally expected to provide a proposed man page update
in parallel? Or somewhat later, when the kernel API change has some
appreciable level of agreement?

Normally we ask for man page updates to be presented at the same
time, as the man page defines the user interface that is being
implemented. In this case, we need updates for the pwritev2() man
page to document RWF_ATOMIC semantics, and the statx() man page to
document what the variables being exposed mean w.r.t. RWF_ATOMIC.

The pwritev2() man page is probably the most important one right now
- it needs to explain the guarantees that RWF_ATOMIC is supposed to
provide w.r.t. data integrity, IO ordering, persistence, etc.
Indeed, it will need to explain exactly how this "multi-atomic-unit
mulit-bio non-atomic RWF_ATOMIC" IO thing can be used safely and
reliably, especially w.r.t. IO ordering and persistence guarantees
in the face of crashes and power failures. Not to mention
documenting error conditions specific to RWF_ATOMIC...

It's all well and good to have some implementation, but without
actually defining and documenting the*guarantees*  that RWF_ATOMIC
provides userspace it is completely useless for application
developers. And from the perspective of a reviewer, without the
documentation stating what the infrastructure actually guarantees
applications, we can't determine if the implementation being
presented is fit for purpose....

ok, understood. Obviously from any discussion so far there are many details
which the user needs to know about how to use this interface and what to
expect.

We'll look to start working on those man page details now.

Agreed.  The manpage contents are what needs to get worked on at LSFMM
where you'll have various block/fs/storage device people in the same
room with which to discuss various issues and try to smooth out the
misundertandings.

(Also: I've decided to cancel my in-person attendance due to a sudden
health issue.   I'll still be in the room, just virtually now. :()

--D

Thanks,
John