> If the hardware supports it, the best way to deal with it is to set
> up
> the driver so that it only ever deals in single pages.
I am working on fixing the driver to support NETIF_F_SG and have changed how it
receives packets to follow how the e1000 driver does it.
Here is where I am at:
When I get the first part of the frame, I allocate an skb for the packet. I
call dev->page = alloc_page(GFP_ATOMIC) to allocate a page for the 4080 bytes
coming from the MAL.
I then setup a DMA mapping for that page to get the data out of the MAL (the
original code simply used dma_map_single, but I need a page).
Once the DMA map has been setup and data transferred, I call
skb_fill_page_desc() to put the data into the skb. I then wrote a function
called emac_consume_page, which unmaps the DMA mapping, frees the page, and
updates the lengths in the skb.
The relevant source code is at the end of this email.
My problem is this:
When I run this code, it appears to create the fragmented packet just fine, but
when it passes it up the stack, the kernel spits out these bugs, one after
another:
BUG: Bad page state in process swapper pfn:0ee9b
page:c051f360 flags:(null) count:-3 mapcount:0 mapping:(null) index:766
Call Trace:
[c032bc30] [c0006ef0] show_stack+0x44/0x16c (unreliable)
[c032bc70] [c006c438] bad_page+0x94/0x130
[c032bc90] [c006d4a0] get_page_from_freelist+0x458/0x4d4
[c032bd20] [c006d5f4] __alloc_pages_nodemask+0xd8/0x4f8
[c032bda0] [c01a1174] emac_poll_rx+0x300/0x9c8
[c032bdf0] [c019cb64] mal_poll+0xa8/0x1ec
[c032be20] [c01cf218] net_rx_action+0x9c/0x1b4
[c032be50] [c0039678] __do_softirq+0xc4/0x148
[c032be90] [c0004d18] do_softirq+0x78/0x80
[c032bea0] [c0039264] irq_exit+0x64/0x7c
[c032beb0] [c0005210] do_IRQ+0x9c/0xb4
[c032bed0] [c000fa7c] ret_from_except+0x0/0x18
[c032bf90] [c000808c] cpu_idle+0xdc/0xec
[c032bfb0] [c00028fc] rest_init+0x70/0x84
[c032bfc0] [c02e0864] start_kernel+0x240/0x2c4
[c032bff0] [c0002254] start_here+0x44/0xb0
BUG: Bad page state in process swapper pfn:0ee8c
page:c051f180 flags:(null) count:-3 mapcount:0 mapping:(null) index:757
Call Trace:
[c032bc30] [c0006ef0] show_stack+0x44/0x16c (unreliable)
[c032bc70] [c006c438] bad_page+0x94/0x130
[c032bc90] [c006d4a0] get_page_from_freelist+0x458/0x4d4
[c032bd20] [c006d5f4] __alloc_pages_nodemask+0xd8/0x4f8
[c032bda0] [c01a1174] emac_poll_rx+0x300/0x9c8
[c032bdf0] [c019cb64] mal_poll+0xa8/0x1ec
[c032be20] [c01cf218] net_rx_action+0x9c/0x1b4
[c032be50] [c0039678] __do_softirq+0xc4/0x148
[c032be90] [c0004d18] do_softirq+0x78/0x80
[c032bea0] [c0039264] irq_exit+0x64/0x7c
[c032beb0] [c0005210] do_IRQ+0x9c/0xb4
[c032bed0] [c000fa7c] ret_from_except+0x0/0x18
[c032bf90] [c000808c] cpu_idle+0xdc/0xec
[c032bfb0] [c00028fc] rest_init+0x70/0x84
[c032bfc0] [c02e0864] start_kernel+0x240/0x2c4
[c032bff0] [c0002254] start_here+0x44/0xb0
I know that I am missing something when it comes to allocating the pages for
the fragments, but when I compare my methodology to the e1000 driver, they
appear to be functionally the same?
Any ideas? I can send the entire source file for the driver if needs be.
Thanks!
Jonathan
Here is the source:
static int emac_poll_rx(void *param, int budget)
{
... /* Other code is here */
push_packet:
skb->dev = dev->ndev;
skb->protocol = eth_type_trans(skb, dev->ndev);
emac_rx_csum(dev, skb, ctrl);
if (unlikely(netif_receive_skb(skb) == NET_RX_DROP))
++dev->estats.rx_dropped_stack;
next:
++dev->stats.rx_packets;
skip:
dev->stats.rx_bytes += len;
slot = (slot + 1) % NUM_RX_BUFF;
--budget;
++received;
continue;
sg:
if (ctrl & MAL_RX_CTRL_FIRST) {
BUG_ON(dev->rx_sg_skb);
if (unlikely(emac_alloc_rx_skb2(dev, slot, GFP_ATOMIC))) {
DBG(dev, "rx OOM %d (%d) (%d)" NL, slot, dev->rx_skb_size, len);
++dev->estats.rx_dropped_oom;
emac_recycle_rx_skb(dev, slot, 0);
} else {
dev->rx_sg_skb = skb;
skb_fill_page_desc(dev->rx_sg_skb, 0, dev->page, 0, len);
emac_consume_page(dev, len, slot);
dev->rx_sg_skb->len += ETH_HLEN;
}
} else if (!emac_rx_sg_append(dev, slot) && (ctrl & MAL_RX_CTRL_LAST)) {
skb = dev->rx_sg_skb;
dev->rx_sg_skb = NULL;
ctrl &= EMAC_BAD_RX_MASK;
if (unlikely(ctrl && ctrl != EMAC_RX_TAH_BAD_CSUM)) {
emac_parse_rx_error(dev, ctrl);
++dev->estats.rx_dropped_error;
dev_kfree_skb(skb);
len = 0;
} else
goto push_packet;
}
... /* Other code is here */
} /* end of emac_poll_rx */
static inline int emac_alloc_rx_skb2(struct emac_instance *dev, int slot,
gfp_t flags)
{
struct sk_buff *skb = alloc_skb(242, flags);
if (unlikely(!skb))
return -ENOMEM;
dev->rx_skb[slot] = skb;
dev->rx_desc[slot].data_len = 0;
dev->page = alloc_page(flags);
DBG(dev, "emac_alloc_skb2: page %x" NL, dev->page);
if(unlikely(!dev->page))
{
return -1;
}
dev->rx_desc[slot].data_ptr = dma_map_page(&dev->ofdev->dev, dev->page,
0, 4096, DMA_FROM_DEVICE);
wmb();
dev->rx_desc[slot].ctrl = MAL_RX_CTRL_EMPTY |
(slot == (NUM_RX_BUFF - 1) ? MAL_RX_CTRL_WRAP : 0);
return 0;
} /* end of emac_alloc_rx_skb2 */
static inline void emac_consume_page(struct emac_instance* dev, int length, int
slot)
{
dma_unmap_page(&dev->ofdev->dev, dev->rx_desc[slot].data_ptr, 4096,
DMA_FROM_DEVICE);
wmb();
__free_page(dev->page);
dev->page = NULL;
dev->rx_sg_skb->len += length;
dev->rx_sg_skb->data_len += length;
dev->rx_sg_skb->truesize += length;
}
static inline int emac_rx_sg_append(struct emac_instance *dev, int slot)
{
if (likely(dev->rx_sg_skb != NULL)) {
int len = dev->rx_desc[slot].data_len;
int tot_len = dev->rx_sg_skb->len + len;
if (unlikely(tot_len + 2 > dev->max_mtu)) {
++dev->estats.rx_dropped_mtu;
dev_kfree_skb(dev->rx_sg_skb);
dev->rx_sg_skb = NULL;
} else {
dev->page = alloc_page(GFP_ATOMIC);
if(unlikely(!dev->page))
{
return -ENOMEM;
}
dev->rx_desc[slot].data_ptr =
dma_map_page(&dev->ofdev->dev, dev->page, 0, 4096, DMA_FROM_DEVICE);
dev->rx_desc[slot].data_len = 0;
wmb();
dev->rx_desc[slot].ctrl = MAL_RX_CTRL_EMPTY | (slot ==
(NUM_RX_BUFF - 1) ? MAL_RX_CTRL_WRAP : 0);
skb_fill_page_desc(dev->rx_sg_skb,
skb_shinfo(dev->rx_sg_skb)->nr_frags, dev->page, 0, len);
emac_consume_page(dev, len, slot);
return 0;
}
}
emac_recycle_rx_skb(dev, slot, 0);
return -1;
} /* end of emac_rx_sg_append */
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
