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

From: David Miller [mailto:davem@davemloft.net]
Sent: Tuesday, June 28, 2016 17:34
To: Dexuan Cui <decui@microsoft.com>
Cc: gregkh@linuxfoundation.org; netdev@vger.kernel.org; linux-
kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
apw@canonical.com; jasowang@redhat.com; vkuznets@redhat.com;
cavery@redhat.com; KY Srinivasan [off-list ref]; Haiyang Zhang
[off-list ref]; joe@perches.com
Subject: Re: [PATCH v12 net-next 1/1] hv_sock: introduce Hyper-V Sockets

From: Dexuan Cui <decui@microsoft.com>
Date: Fri, 24 Jun 2016 07:45:24 +0000

quoted

+	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