Re: [Lsf-pc] [LSF/MM/BPF TOPIC] Buffered atomic writes

[Christoph Hellwig <hch@lst.de>]

On Wed, Feb 18, 2026 at 11:26:06AM +1100, Dave Chinner wrote:
> ISTR mentioning that we should be doing exactly this (grab page
> cache pages, fill them and submit them through the DIO path) for
> O_DSYNC buffered writethrough IO a long time again.

Yes, multiple times.  And I did a few more times since then.

> Regardless, we are here again with proposals for RWF_ATOMIC and
> RWF_WRITETHROUGH and a suggestion that maybe we should vector
> buffered writethrough via the DIO path.....
> 
> Perhaps it's time to do this?

Yes.

> FWIW, the other thing that write-through via the DIO path enables is
> true async O_DSYNC buffered IO. Right now O_DSYNC buffered writes
> block waiting on IO completion through generic_sync_write() ->
> vfs_fsync_range(), even when issued through AIO paths.  Vectoring it
> through the DIO path avoids the blocking fsync path in IO submission
> as it runs in the async DIO completion path if it is needed....

It's only true if we can do the page cache updates non-blocking, but
in many cases that should indeed be possible.