RE: [PATCH v12 net-next 1/1] hv_sock: introduce Hyper-V Sockets

[Dexuan Cui]

> From: David Miller [mailto:davem@xxxxxxxxxxxxx]
> Sent: Tuesday, June 28, 2016 17:34
> To: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Cc: gregkh@xxxxxxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx;
> apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx; vkuznets@xxxxxxxxxx;
> cavery@xxxxxxxxxx; KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
> <haiyangz@xxxxxxxxxxxxx>; joe@xxxxxxxxxxx
> Subject: Re: [PATCH v12 net-next 1/1] hv_sock: introduce Hyper-V Sockets
> 
> From: Dexuan Cui <decui@xxxxxxxxxxxxx>
> Date: Fri, 24 Jun 2016 07:45:24 +0000
> 
> > +	while ((ret = vmalloc(size)) == NULL)
> > +		ssleep(1);
> 
> This is completely, and entirely, unacceptable.
> 
> If the allocation fails, you return an error and release
> your resources.
> 
> You don't just loop forever waiting for it to succeed.

Hi David,
I agree this is ugly...

The idea here is: IMO the syscalls sys_read()/write() shoudn't return
-ENOMEM, so I have to make sure the buffer allocation succeeds?

I tried to use kmalloc with __GFP_NOFAIL, but I hit a warning in 
in mm/page_alloc.c:
WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));

What error code do you think I should return? 
EAGAIN, ERESTARTSYS, or something else?

May I have your suggestion? Thanks!

-- Dexuan