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https://github.com/torvalds/linux
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f8e8f97c11
Dmitry Kravkov reported packet drops for GRE packets since GRO support
was added.
There is a race in gro_cell_poll() because we call napi_complete()
without any synchronization with a concurrent gro_cells_receive()
Once bug was triggered, we queued packets but did not schedule NAPI
poll.
We can fix this issue using the spinlock protected the napi_skbs queue,
as we have to hold it to perform skb dequeue anyway.
As we open-code skb_dequeue(), we no longer need to mask IRQS, as both
producer and consumer run under BH context.
Bug added in commit c9e6bc644e (net: add gro_cells infrastructure)
Reported-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
107 lines
2.4 KiB
C
107 lines
2.4 KiB
C
#ifndef _NET_GRO_CELLS_H
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#define _NET_GRO_CELLS_H
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <linux/netdevice.h>
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struct gro_cell {
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struct sk_buff_head napi_skbs;
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struct napi_struct napi;
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} ____cacheline_aligned_in_smp;
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struct gro_cells {
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unsigned int gro_cells_mask;
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struct gro_cell *cells;
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};
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static inline void gro_cells_receive(struct gro_cells *gcells, struct sk_buff *skb)
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{
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struct gro_cell *cell = gcells->cells;
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struct net_device *dev = skb->dev;
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if (!cell || skb_cloned(skb) || !(dev->features & NETIF_F_GRO)) {
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netif_rx(skb);
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return;
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}
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if (skb_rx_queue_recorded(skb))
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cell += skb_get_rx_queue(skb) & gcells->gro_cells_mask;
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if (skb_queue_len(&cell->napi_skbs) > netdev_max_backlog) {
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atomic_long_inc(&dev->rx_dropped);
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kfree_skb(skb);
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return;
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}
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/* We run in BH context */
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spin_lock(&cell->napi_skbs.lock);
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__skb_queue_tail(&cell->napi_skbs, skb);
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if (skb_queue_len(&cell->napi_skbs) == 1)
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napi_schedule(&cell->napi);
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spin_unlock(&cell->napi_skbs.lock);
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}
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/* called unser BH context */
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static inline int gro_cell_poll(struct napi_struct *napi, int budget)
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{
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struct gro_cell *cell = container_of(napi, struct gro_cell, napi);
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struct sk_buff *skb;
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int work_done = 0;
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spin_lock(&cell->napi_skbs.lock);
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while (work_done < budget) {
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skb = __skb_dequeue(&cell->napi_skbs);
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if (!skb)
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break;
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spin_unlock(&cell->napi_skbs.lock);
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napi_gro_receive(napi, skb);
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work_done++;
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spin_lock(&cell->napi_skbs.lock);
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}
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if (work_done < budget)
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napi_complete(napi);
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spin_unlock(&cell->napi_skbs.lock);
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return work_done;
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}
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static inline int gro_cells_init(struct gro_cells *gcells, struct net_device *dev)
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{
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int i;
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gcells->gro_cells_mask = roundup_pow_of_two(netif_get_num_default_rss_queues()) - 1;
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gcells->cells = kcalloc(sizeof(struct gro_cell),
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gcells->gro_cells_mask + 1,
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GFP_KERNEL);
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if (!gcells->cells)
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return -ENOMEM;
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for (i = 0; i <= gcells->gro_cells_mask; i++) {
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struct gro_cell *cell = gcells->cells + i;
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skb_queue_head_init(&cell->napi_skbs);
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netif_napi_add(dev, &cell->napi, gro_cell_poll, 64);
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napi_enable(&cell->napi);
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}
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return 0;
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}
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static inline void gro_cells_destroy(struct gro_cells *gcells)
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{
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struct gro_cell *cell = gcells->cells;
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int i;
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if (!cell)
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return;
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for (i = 0; i <= gcells->gro_cells_mask; i++,cell++) {
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netif_napi_del(&cell->napi);
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skb_queue_purge(&cell->napi_skbs);
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}
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kfree(gcells->cells);
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gcells->cells = NULL;
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}
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#endif
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