On Thu, Mar 22, 2018 at 06:16:53PM +0000, Al Viro wrote:

On Thu, Mar 22, 2018 at 06:24:10PM +0100, Christoph Hellwig wrote:

quoted

-static void aio_complete(struct aio_kiocb *iocb, long res, long res2)
+static bool aio_complete(struct aio_kiocb *iocb, long res, long res2,
+		unsigned complete_flags)

Looks like all callers are following that with "if returned true,
fput(something)".  Does it really make any sense to keep that struct
file * in different fields?

struct kiocb is used not just for aio, but for our normal read/write_iter
APIs, and it is not suitable for poll or fsync.  So I can't really find
a good way to keep it common except for duplicating it in struct kiocb
and strut aio_iocb.  But maybe we could pass a struct file argument
to aio_complete().

Wait a sec...  What ordering do we want for
	* call(s) of ->ki_complete
	* call (if any) of ->ki_cancel
	* dropping reference to struct file
and what are the expected call chains for all of those?

fput must be done exactly once from inside ->ki_complete OR ->ki_cancel
in case it did manage to do the actual completion.  Reference to struct
file isn't needed in aio_complete, but if aio_complete decided who
won the race we'll have to put after it (or inside it if we want to make
it common)

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