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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