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SubjectRe: [PATCH 2/2] aio: propogate post-EIOCBQUEUED errors to completion event
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> This is an interesting trick, but I'd like to consider hard whether  
> the added
> complexity is worth it. Could you list the various other cases you
> have in mind
> which would want to use it ?

I'm happy to report that the sync case and the
invalidate_inode_pages2_range() case are the only two which try to
rewrite 'ret'. I audited all the call paths between aio_{read,write}
and -EIOCBQUUEUED.
So, sure, maybe we can shuffle the house of cards a little in the
direction away from having a fs/aio.c helper for the situation by
simply removing the few current instances of the problem. It won't
scale as people add problems without knowing about the rule to not
overwrite -EIOCBQUEUED, but hopefully that won't be a rule for much
longer :) :).

For the O_SYNC case we could add another magical test to the is_async
assignment which won't perform AIO on O_SYNC descriptors.

> For the invalidate_inode_pages2_range() case, I wonder if the right
> place to issue this is after the direct IO write has completed and
> before
> aio_complete() is issued (somewhat like the way we do
> bio_check_pages_dirty
> for DIO reads), rather than after submission when the IO may still
> not have
> hit the disk. This would also make the behaviour uniform for
> synchronous and
> async cases.

Hmm, I think I like that. It solves the problem for the current sole
user of -EIOCBQUEUED without too much disruption.

> BTW, am I right in interpreting that with your change aio_complete
> () may
> trigger an io_getevents() wakeup, before the corresponding event is
> placed
> on the ring buffer ?

Hmm, yeah, it looks like I goofed that.

I'll roll a patch which does the invalidation down in fs/direct-io.c.

- z
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