Re: [PATCH v7 2/9] fs: Initial atomic write support

Christoph Hellwig
2024-06-06T05:41:49Z

On Wed, Jun 05, 2024 at 11:48:12AM +0100, John Garry wrote:
> I have no strong attachment to that name (atomic).
>
> For both SCSI and NVMe, it's an "atomic" feature and I was basing the
> naming on that.
>
> We could have RWF_NOTEARS or RWF_UNTEARABLE_WRITE or RWF_UNTEARABLE or
> RWF_UNTORN or similar. Any preference?

No particular preference between any of the option including atomic.
Just mumbling out aloud my thoughts :)

> For io_uring/rw.c, we have io_write() -> io_rw_init_file(..., WRITE), and
> then later we set IOCB_WRITE, so would be neat to use there. But then
> do_iter_readv_writev() does not set IOCB_WRITE - I can't imagine that
> setting IOCB_WRITE would do any harm there. I see a similar change in
> https://lore.kernel.org/linux-fsdevel/167391048988.2311931.1567396746365286847.stgit@warthog.procyon.org.uk/
>
> AFAICS, setting IOCB_WRITE is quite inconsistent. From browsing through
> fsdevel on lore, there was some history in trying to use IOCB_WRITE always
> instead of iov_iter direction. Any idea what happened to that?
>
> I'm just getting the feeling that setting IOCB_WRITE in
> kiocb_set_rw_flags() is a small part - and maybe counter productive - of a
> larger job of fixing IOCB_WRITE usage.

Someone (IIRC Dave H.) want to move it into the iov_iter a while ago.
I think that is a bad idea - the iov_iter is a data container except
for the shoehorned in read/write information doesn't describe the
operation at all. So using the flag in the iocb seems like the better
architecture. But I can understand that you might want to stay out
of all of this, so let's not touch IOCB_WRITE here.