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Date: Fri, 6 Apr 2018 08:27:00 +0200
From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>, Avi Kivity <avi@scylladb.com>,
        linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
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Subject: Re: io_pgetevents & aio fsync V2
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References: <20180328072639.16885-1-hch@lst.de> <20180406031630.GU30522@ZenIV.linux.org.uk>
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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..