linux-kernel - Re: [PATCH 0/2] rcu: Transform kfree_rcu() into kvfree

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Date:   Tue, 6 Feb 2018 20:23:34 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Kirill Tkhai <ktkhai@...tuozzo.com>, josh@...htriplett.org,
        rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        jiangshanlai@...il.com, mingo@...hat.com, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, brouer@...hat.com, rao.shoaib@...cle.com
Subject: Re: [PATCH 0/2] rcu: Transform kfree_rcu() into kvfree_rcu()

On Tue, Feb 06, 2018 at 06:17:03PM -0800, Paul E. McKenney wrote:
> So it is OK to kvmalloc() something and pass it to either kfree() or
> kvfree(), and it had better be OK to kvmalloc() something and pass it
> to kvfree().
> 
> Is it OK to kmalloc() something and pass it to kvfree()?

Yes, it absolutely is.

void kvfree(const void *addr)
{
        if (is_vmalloc_addr(addr))
                vfree(addr);
        else
                kfree(addr);
}

> If so, is it really useful to have two different names here, that is,
> both kfree_rcu() and kvfree_rcu()?

I think it's handy to have all three of kvfree_rcu(), kfree_rcu() and
vfree_rcu() available in the API for the symmetry of calling kmalloc()
/ kfree_rcu().

Personally, I would like us to rename kvfree() to just free(), and have
malloc(x) be an alias to kvmalloc(x, GFP_KERNEL), but I haven't won that
fight yet.