linux-kernel - Re: [PATCH 3/3] hv: vmbus_open(): reset the channel state on ENOMEM

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Date:	Thu, 29 Jan 2015 14:22:20 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	Dexuan Cui <decui@...rosoft.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	driverdev-devel@...uxdriverproject.org, olaf@...fle.de,
	apw@...onical.com, jasowang@...hat.com, kys@...rosoft.com,
	haiyangz@...rosoft.com
Subject: Re: [PATCH 3/3] hv: vmbus_open(): reset the channel state on ENOMEM

Dexuan Cui <decui@...rosoft.com> writes:

> Without this patch, the state is put to CHANNEL_OPENING_STATE, and when
> the driver is loaded next time, vmbus_open() will fail immediately due to
> newchannel->state != CHANNEL_OPEN_STATE.

The patch makes sense, but I have one small doubt. We call vmbus_open
from probe functions of various devices. E.g. in hyperv-keyboard we
have:
 error = vmbus_open(...)
 if (error)
     goto err_free_mem;

and we don't call vmbus_close(...) on this path so no
CHANNELMSG_CLOSECHANNEL will be send. Who's gonna retry probe? Wouldn't
it be better to close the channel?

>
> CC: "K. Y. Srinivasan" <kys@...rosoft.com>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
>  drivers/hv/channel.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 2978f5e..26dcf26 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -89,9 +89,10 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
>  	out = (void *)__get_free_pages(GFP_KERNEL|__GFP_ZERO,
>  		get_order(send_ringbuffer_size + recv_ringbuffer_size));
>
> -	if (!out)
> -		return -ENOMEM;
> -
> +	if (!out) {
> +		err = -ENOMEM;
> +		goto error0;
> +	}
>
>  	in = (void *)((unsigned long)out + send_ringbuffer_size);
>
> @@ -199,6 +200,7 @@ error0:
>  	free_pages((unsigned long)out,
>  		get_order(send_ringbuffer_size + recv_ringbuffer_size));
>  	kfree(open_info);
> +	newchannel->state = CHANNEL_OPEN_STATE;
>  	return err;
>  }
>  EXPORT_SYMBOL_GPL(vmbus_open);

-- 
  Vitaly
--
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