Re: [PATCH] xfs: report a writeback error on a read() call

[Christoph Hellwig]

On Wed, Jun 25, 2025 at 06:40:07AM -0400, Jeff Layton wrote:
> Another option:
> 
> We could expose this functionality in preadv2() with a new RWF_WBERR
> flag (better names welcome). That way applications could opt-in to
> checking for writeback errors like this. With that, the application is
> at least explicitly saying that it wants this behavior.

That sounds like a really strange interface to me.

I have to admit I don't fully understand the use case where an
application cares about these errors, but also doesn't use f(data)sync
or sync(fs) to actually persist the data.  If we can come up with a
coherent use case for that we should simply add a new syscall or fcntl
to query the delayed writeback errors instead of overloading other
interfaces.