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

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Message-Id: <20180207021703.GC3617@linux.vnet.ibm.com>
Date:   Tue, 6 Feb 2018 18:17:03 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     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 01:19:29PM +0300, Kirill Tkhai wrote:
> Recent times kvmalloc() begun widely be used in kernel.
> Some of such memory allocations have to be freed after
> rcu grace period, and this patchset introduces a generic
> primitive for doing this.
> 
> Actually, everything is made in [1/2]. Patch [2/2] is just
> added to make new kvfree_rcu() have the first user.
> 
> The patch [1/2] transforms kfree_rcu(), its sub definitions
> and its sub functions into kvfree_rcu() form. The most
> significant change is in __rcu_reclaim(), where kvfree()
> is used instead of kfree(). Since kvfree() is able to
> have a deal with memory allocated via kmalloc(), vmalloc()
> and kvmalloc(); kfree_rcu() and vfree_rcu() may simply
> be defined through this new kvfree_rcu().

Interesting.

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()?

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

Also adding Jesper and Rao on CC for their awareness.

							Thanx, Paul

> ---
> 
> Kirill Tkhai (2):
>       rcu: Transform kfree_rcu() into kvfree_rcu()
>       mm: Use kvfree_rcu() in update_memcg_params()
> 
> 
>  include/linux/rcupdate.h   |   31 +++++++++++++++++--------------
>  include/linux/rcutiny.h    |    4 ++--
>  include/linux/rcutree.h    |    2 +-
>  include/trace/events/rcu.h |   12 ++++++------
>  kernel/rcu/rcu.h           |    8 ++++----
>  kernel/rcu/tree.c          |   14 +++++++-------
>  kernel/rcu/tree_plugin.h   |   10 +++++-----
>  mm/slab_common.c           |   10 +---------
>  8 files changed, 43 insertions(+), 48 deletions(-)
> 
> --
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
>