Re: io_pgetevents & aio fsync V2

Christoph Hellwig
2018-04-06T06:27:03Z

On Fri, Apr 06, 2018 at 04:16:30AM +0100, Al Viro wrote:
> BTW, this is only tangentially related, but... does *anything* call
> io_submit() for huge amounts of iocb? Check in do_io_submit() is
> insane - "no more than MAX_LONG total of _pointers_". Compat variant
> goes for "no more than a page worth of pointers" and there's
> a hard limit in ioctx_alloc() - we can't ever get more than
> 8M slots in ring buffer...

Logical upper bound for io_submit is nr_events passed to io_setup(),
which is bound by aio_max_nr. Except that we never actually check
against nr_events (or max_reqs as it is known in kernel) in io_submit.
Sigh..