netdev - Re: [PATCH] net: suppress warnings on dev_alloc

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Date:	Wed, 18 May 2016 13:48:15 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] net: suppress warnings on dev_alloc_skb

On Wed, May 18, 2016 at 12:29 PM, Neil Horman <nhorman@...driver.com> wrote:
> On Wed, May 18, 2016 at 10:57:21AM -0700, Alexander Duyck wrote:
>> On Wed, May 18, 2016 at 9:01 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> > On Wed, 2016-05-18 at 11:25 -0400, Neil Horman wrote:
>> >> Noticed an allocation failure in a network driver the other day on a 32 bit
>> >> system:
>> >>
>> >> DMA-API: debugging out of memory - disabling
>> >> bnx2fc: adapter_lookup: hba NULL
>> >> lldpad: page allocation failure. order:0, mode:0x4120
>> >> Pid: 4556, comm: lldpad Not tainted 2.6.32-639.el6.i686.debug #1
>> >> Call Trace:
>> >>  [<c08a4086>] ? printk+0x19/0x23
>> >>  [<c05166a4>] ? __alloc_pages_nodemask+0x664/0x830
>> >>  [<c0649d02>] ? free_object+0x82/0xa0
>> >>  [<fb4e2c9b>] ? ixgbe_alloc_rx_buffers+0x10b/0x1d0 [ixgbe]
>> >>  [<fb4e2fff>] ? ixgbe_configure_rx_ring+0x29f/0x420 [ixgbe]
>> >>  [<fb4e228c>] ? ixgbe_configure_tx_ring+0x15c/0x220 [ixgbe]
>> >>  [<fb4e3709>] ? ixgbe_configure+0x589/0xc00 [ixgbe]
>> >>  [<fb4e7be7>] ? ixgbe_open+0xa7/0x5c0 [ixgbe]
>> >>  [<fb503ce6>] ? ixgbe_init_interrupt_scheme+0x5b6/0x970 [ixgbe]
>> >>  [<fb4e8e54>] ? ixgbe_setup_tc+0x1a4/0x260 [ixgbe]
>> >>  [<fb505a9f>] ? ixgbe_dcbnl_set_state+0x7f/0x90 [ixgbe]
>> >>  [<c088d80d>] ? dcb_doit+0x10ed/0x16d0
>> >> ...
>> >
>> >
>> > Well, maybe this call site (via ixgbe_configure_rx_ring()) should be
>> > using GFP_KERNEL instead of GFP_ATOMIC.
>>
>> The problem is the ixgbe driver is using the same function for
>> allocating memory in the softirq and in the init.  As such it has to
>> default to GFP_ATOMIC so that it doesn't screw up the NAPI allocation
>> case.
>>
>
> I suppose a happy medium would be to extend dev_alloc_pages to accept a gfp
> argument, and then have the function itself only set __GFP_NOWARN, if ATOMIC is
> also set?

Why bother?  I really think Eric's patch is the way to go.

We can already pass gfp flags to __dev_alloc_pages so if we need to
pass flags we can use that.  Otherwise for the users of dev_alloc_page
and dev_alloc_pages we can just pass GFP_ATOMIC | __GFP_NOWARN like
Eric did in his example patch.

- Alex