On 2019-09-05, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
On Thu, Sep 05, 2019 at 08:23:03PM +0200, Christian Brauner wrote:Because every caller of that function right now has that limit set anyway iirc. So we can either remove it from here and place it back for the individual callers or leave it in the helper. Also, I'm really asking, why not? Is it unreasonable to have an upper bound on the size (for a long time probably) or are you disagreeing with PAGE_SIZE being used? PAGE_SIZE limit is currently used by sched, perf, bpf, and clone3 and in a few other places.For a primitive that can be safely used with any size (OK, any within the usual 2Gb limit)? Why push the random policy into the place where it doesn't belong? Seriously, what's the point? If they want to have a large chunk of userland memory zeroed or checked for non-zeroes - why would that be a problem?
Thinking about it some more, there isn't really any r/w amplification -- so there isn't much to gain by passing giant structs. Though, if we are going to permit 2GB buffers, isn't that also an argument to use memchr_inv()? :P -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH <https://www.cyphar.com/>
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