netdev - Re: [PATCH 1/7] netpoll: use GFP_ATOMIC in slave_enable_netpoll() and __netpoll

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Message-ID: <1343985428.9299.868.camel@edumazet-glaptop>
Date:	Fri, 03 Aug 2012 11:17:08 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <amwang@...hat.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	Joe Perches <joe@...ches.com>,
	Neil Horman <nhorman@...driver.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] netpoll: use GFP_ATOMIC in slave_enable_netpoll()
 and __netpoll_setup()

On Fri, 2012-07-27 at 23:37 +0800, Cong Wang wrote:
> slave_enable_netpoll() and __netpoll_setup() may be called
> with read_lock() held, so should use GFP_ATOMIC to allocate
> memory.
> 
> Cc: "David S. Miller" <davem@...emloft.net>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Cong Wang <amwang@...hat.com>
> ---
>  drivers/net/bonding/bond_main.c |    2 +-
>  net/core/netpoll.c              |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 6fae5f3..ab773d4 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1235,7 +1235,7 @@ static inline int slave_enable_netpoll(struct slave *slave)
>  	struct netpoll *np;
>  	int err = 0;
>  
> -	np = kzalloc(sizeof(*np), GFP_KERNEL);
> +	np = kzalloc(sizeof(*np), GFP_ATOMIC);
>  	err = -ENOMEM;
>  	if (!np)
>  		goto out;
> diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> index b4c90e4..c78a966 100644
> --- a/net/core/netpoll.c
> +++ b/net/core/netpoll.c
> @@ -734,7 +734,7 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
>  	}
>  
>  	if (!ndev->npinfo) {
> -		npinfo = kmalloc(sizeof(*npinfo), GFP_KERNEL);
> +		npinfo = kmalloc(sizeof(*npinfo), GFP_ATOMIC);
>  		if (!npinfo) {
>  			err = -ENOMEM;
>  			goto out;

Yes this works, but maybe you instead could pass/add a gfp_t flags
argument to __netpoll_setup() ?

Management tasks should allow GFP_KERNEL allocations to have less
failure risks.

Its sad bonding uses the rwlock here instead of a mutex



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