linux-kernel - Re: [PATCH] mm/page_owner: use vmalloc instead of kmalloc

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Message-ID: <1540540867.21297.2.camel@mtkswgap22>
Date:   Fri, 26 Oct 2018 16:01:07 +0800
From:   Miles Chen <miles.chen@...iatek.com>
To:     Joe Perches <joe@...ches.com>
CC:     Matthias Brugger <matthias.bgg@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <wsd_upstream@...iatek.com>, <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mm/page_owner: use vmalloc instead of kmalloc

On Thu, 2018-10-25 at 11:44 -0700, Joe Perches wrote:
> On Fri, 2018-10-26 at 02:34 +0800, miles.chen@...iatek.com wrote:
> > From: Miles Chen <miles.chen@...iatek.com>
> > 
> > The kbuf used by page owner is allocated by kmalloc(),
> > which means it can use only normal memory and there might
> > be a "out of memory" issue when we're out of normal memory.
> > 
> > Use vmalloc() so we can also allocate kbuf from highmem
> > on 32bit kernel.
> 
> If this is really necessary, using kvmalloc/kvfree would
> be better as the vmalloc space is also limited.

thanks for the advise.
kvmalloc/kvfree is better here.

> 
> > diff --git a/mm/page_owner.c b/mm/page_owner.c
> []
> > @@ -1,7 +1,6 @@
> >  // SPDX-License-Identifier: GPL-2.0
> >  #include <linux/debugfs.h>
> >  #include <linux/mm.h>
> > -#include <linux/slab.h>
> >  #include <linux/uaccess.h>
> >  #include <linux/bootmem.h>
> >  #include <linux/stacktrace.h>
> > @@ -10,6 +9,7 @@
> >  #include <linux/migrate.h>
> >  #include <linux/stackdepot.h>
> >  #include <linux/seq_file.h>
> > +#include <linux/vmalloc.h>
> >  
> >  #include "internal.h"
> >  
> > @@ -351,7 +351,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
> >  		.skip = 0
> >  	};
> >  
> > -	kbuf = kmalloc(count, GFP_KERNEL);
> > +	kbuf = vmalloc(count);
> >  	if (!kbuf)
> >  		return -ENOMEM;
> >  
> > @@ -397,11 +397,11 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
> >  	if (copy_to_user(buf, kbuf, ret))
> >  		ret = -EFAULT;
> >  
> > -	kfree(kbuf);
> > +	vfree(kbuf);
> >  	return ret;
> >  
> >  err:
> > -	kfree(kbuf);
> > +	vfree(kbuf);
> >  	return -ENOMEM;
> >  }
> >  
>