Re: [PATCH RFC] ipmi: use vzalloc instead of kmalloc for user creation

[Feng Tang]

Hi Corey,

On Fri, Apr 17, 2020 at 09:00:06PM -0500, Corey Minyard wrote:
> On Fri, Apr 17, 2020 at 01:01:29PM +0800, Feng Tang wrote:
> > We met mulitple times of failure of staring bmc-watchdog,
> > due to the runtime memory allocation failure of order 4.
> 
> I'm beginning to think that using srcu was a bad idea.  It made things
> cleaner and easier, but it eats tons of memory.  Sigh.

Yes, I was aslo surprised when I first knew the scru_struct is
so big. I thought we may use kmem_cache to dynamically allocate
it, though there are only a few places in kernel.

> Applied, at least for a fix for now.
 
Thanks! It will save us a lot of troubles :)

- Feng

> Thanks,
> 
> -corey
> 
> > 
> >      bmc-watchdog: page allocation failure: order:4, mode:0x40cc0(GFP_KERNEL|__GFP_COMP), nodemask=(null),cpuset=/,mems_allowed=0-1
> >      CPU: 1 PID: 2571 Comm: bmc-watchdog Not tainted 5.5.0-00045-g7d6bb61d6188c #1
> >      Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.00.01.0015.110720180833 11/07/2018
> >      Call Trace:
> >       dump_stack+0x66/0x8b
> >       warn_alloc+0xfe/0x160
> >       __alloc_pages_slowpath+0xd3e/0xd80
> >       __alloc_pages_nodemask+0x2f0/0x340
> >       kmalloc_order+0x18/0x70
> >       kmalloc_order_trace+0x1d/0xb0
> >       ipmi_create_user+0x55/0x2c0 [ipmi_msghandler]
> >       ipmi_open+0x72/0x110 [ipmi_devintf]
> >       chrdev_open+0xcb/0x1e0
> >       do_dentry_open+0x1ce/0x380
> >       path_openat+0x305/0x14f0
> >       do_filp_open+0x9b/0x110
> >       do_sys_open+0x1bd/0x250
> >       do_syscall_64+0x5b/0x1f0
> >       entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > 
> > Using vzalloc/vfree for creating ipmi_user heals the
> > problem.
> > 
> > Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> > ---
> >  drivers/char/ipmi/ipmi_msghandler.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> > index c48d8f0..96f1573 100644
> > --- a/drivers/char/ipmi/ipmi_msghandler.c
> > +++ b/drivers/char/ipmi/ipmi_msghandler.c
> > @@ -1153,7 +1153,7 @@ static void free_user_work(struct work_struct *work)
> >  					      remove_work);
> >  
> >  	cleanup_srcu_struct(&user->release_barrier);
> > -	kfree(user);
> > +	vfree(user);
> >  }
> >  
> >  int ipmi_create_user(unsigned int          if_num,
> > @@ -1185,7 +1185,7 @@ int ipmi_create_user(unsigned int          if_num,
> >  	if (rv)
> >  		return rv;
> >  
> > -	new_user = kmalloc(sizeof(*new_user), GFP_KERNEL);
> > +	new_user = vzalloc(sizeof(*new_user));
> >  	if (!new_user)
> >  		return -ENOMEM;
> >  
> > @@ -1232,7 +1232,7 @@ int ipmi_create_user(unsigned int          if_num,
> >  
> >  out_kfree:
> >  	srcu_read_unlock(&ipmi_interfaces_srcu, index);
> > -	kfree(new_user);
> > +	vfree(new_user);
> >  	return rv;
> >  }
> >  EXPORT_SYMBOL(ipmi_create_user);
> > -- 
> > 2.7.4
> >