On Wed, 3 Jul 2019 13:18:59 +0300 Ivan Khoronzhuk <[email protected]> wrote:
> First of all, it is an absolute requirement that each RX-queue have > their own page_pool object/allocator. And this change is intendant > to handle special case, where a single RX-queue can receive packets > from two different net_devices. > > In order to protect against using same allocator for 2 different rx > queues, add queue_index to xdp_mem_allocator to catch the obvious > mistake where queue_index mismatch, as proposed by Jesper Dangaard > Brouer. > > Adding this on xdp allocator level allows drivers with such dependency > change the allocators w/o modifications. > > Signed-off-by: Ivan Khoronzhuk <[email protected]> > --- > include/net/xdp_priv.h | 2 ++ > net/core/xdp.c | 55 ++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 57 insertions(+) > > diff --git a/include/net/xdp_priv.h b/include/net/xdp_priv.h > index 6a8cba6ea79a..9858a4057842 100644 > --- a/include/net/xdp_priv.h > +++ b/include/net/xdp_priv.h > @@ -18,6 +18,8 @@ struct xdp_mem_allocator { > struct rcu_head rcu; > struct delayed_work defer_wq; > unsigned long defer_warn; > + unsigned long refcnt; > + u32 queue_index; > }; I don't like this approach, because I think we need to extend struct xdp_mem_allocator with a net_device pointer, for doing dev_hold(), to correctly handle lifetime issues. (As I tried to explain previously). This will be much harder after this change, which is why I proposed the other patch. > #endif /* __LINUX_NET_XDP_PRIV_H__ */ > diff --git a/net/core/xdp.c b/net/core/xdp.c > index 829377cc83db..4f0ddbb3717a 100644 > --- a/net/core/xdp.c > +++ b/net/core/xdp.c > @@ -98,6 +98,18 @@ static bool __mem_id_disconnect(int id, bool force) > WARN(1, "Request remove non-existing id(%d), driver bug?", id); > return true; > } > + > + /* to avoid calling hash lookup twice, decrement refcnt here till it > + * reaches zero, then it can be called from workqueue afterwards. > + */ > + if (xa->refcnt) > + xa->refcnt--; > + > + if (xa->refcnt) { > + mutex_unlock(&mem_id_lock); > + return true; > + } > + > xa->disconnect_cnt++; > > /* Detects in-flight packet-pages for page_pool */ > @@ -312,6 +324,33 @@ static bool __is_supported_mem_type(enum xdp_mem_type > type) > return true; > } > > +static struct xdp_mem_allocator *xdp_allocator_find(void *allocator) > +{ > + struct xdp_mem_allocator *xae, *xa = NULL; > + struct rhashtable_iter iter; > + > + if (!allocator) > + return xa; > + > + rhashtable_walk_enter(mem_id_ht, &iter); > + do { > + rhashtable_walk_start(&iter); > + > + while ((xae = rhashtable_walk_next(&iter)) && !IS_ERR(xae)) { > + if (xae->allocator == allocator) { > + xa = xae; > + break; > + } > + } > + > + rhashtable_walk_stop(&iter); > + > + } while (xae == ERR_PTR(-EAGAIN)); > + rhashtable_walk_exit(&iter); > + > + return xa; > +} > + > int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq, > enum xdp_mem_type type, void *allocator) > { > @@ -347,6 +386,20 @@ int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info > *xdp_rxq, > } > } > > + mutex_lock(&mem_id_lock); > + xdp_alloc = xdp_allocator_find(allocator); > + if (xdp_alloc) { > + /* One allocator per queue is supposed only */ > + if (xdp_alloc->queue_index != xdp_rxq->queue_index) > + return -EINVAL; > + > + xdp_rxq->mem.id = xdp_alloc->mem.id; > + xdp_alloc->refcnt++; > + mutex_unlock(&mem_id_lock); > + return 0; > + } > + mutex_unlock(&mem_id_lock); > + > xdp_alloc = kzalloc(sizeof(*xdp_alloc), gfp); > if (!xdp_alloc) > return -ENOMEM; > @@ -360,6 +413,8 @@ int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info > *xdp_rxq, > xdp_rxq->mem.id = id; > xdp_alloc->mem = xdp_rxq->mem; > xdp_alloc->allocator = allocator; > + xdp_alloc->refcnt = 1; > + xdp_alloc->queue_index = xdp_rxq->queue_index; > > /* Insert allocator into ID lookup table */ > ptr = rhashtable_insert_slow(mem_id_ht, &id, &xdp_alloc->node); -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
