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

Miles Chen
2018-10-26T08:01:28Z

On Thu, 2018-10-25 at 11:44 -0700, Joe Perches wrote:
> On Fri, 2018-10-26 at 02:34 +0800, miles.chen@mediatek.com wrote:
> > From: Miles Chen <miles.chen@mediatek.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;
> > }
> >
>