Devices may have limits on the number of fragments in an skb they
support. Current codebase uses a constant as maximum for number of
fragments (MAX_SKB_FRAGS) one skb can hold and use.
When enabling scatter/gather and running traffic with many small
messages the codebase uses the maximum number of fragments and thereby
violates the max for certain devices.
An example of such a violation is when running IPoIB on a HCA
supporting 16 SGE on an architecture with 4K pagesize. The
MAX_SKB_FRAGS will be 17 (64K/4K+1) and because IPoIB adds yet another
segment we end up with send_requests with 18 SGE resulting in
kernel-panic.
The patch allows the device to limit the maximum number fragments used
in one skb.
The functionality corresponds to gso_max_size/gso_max_segs for gso.
Signed-off-by: Hans Westgaard Ry <hans.westgaard...@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bu...@oracle.com>
Reviewed-by: Knut Omang <knut.om...@oracle.com>
Reviewed-by: Wei Lin Guay <wei.lin.g...@oracle.com>
Reviewed-by: Santosh Shilimkar <santosh.shilim...@oracle.com>
Reviewed-by: Yuval Shaia <yuval.sh...@oracle.com>
---
include/linux/netdevice.h | 8 ++++++++
include/net/sock.h | 2 ++
net/core/dev.c | 1 +
net/core/sock.c | 1 +
net/ipv4/tcp.c | 4 ++--
5 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3b5d134..c661865 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1513,6 +1513,8 @@ enum netdev_priv_flags {
* NIC for GSO
* @gso_min_segs: Minimum number of segments that can be passed to the
* NIC for GSO
+ * @sg_max_frags: Maximum number of fragments that can be passed to the
+ * NIC for SG
*
* @dcbnl_ops: Data Center Bridging netlink ops
* @num_tc: Number of traffic classes in the net device
@@ -1799,6 +1801,7 @@ struct net_device {
struct phy_device *phydev;
struct lock_class_key *qdisc_tx_busylock;
bool proto_down;
+ u16 sg_max_frags;
};
#define to_net_dev(d) container_of(d, struct net_device, dev)
@@ -3794,6 +3797,11 @@ static inline void netif_set_gso_max_size(struct
net_device *dev,
{
dev->gso_max_size = size;
}
+static inline void netif_set_sg_max_frags(struct net_device *dev,
+ u16 max)
+{
+ dev->sg_max_frags = min_t(u16, MAX_SKB_FRAGS, max);
+}
static inline void skb_gso_error_unwind(struct sk_buff *skb, __be16 protocol,
int pulled_hlen, u16 mac_offset,
diff --git a/include/net/sock.h b/include/net/sock.h
index 52d27ee..c884104 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -274,6 +274,7 @@ struct cg_proto;
* @sk_gso_type: GSO type (e.g. %SKB_GSO_TCPV4)
* @sk_gso_max_size: Maximum GSO segment size to build
* @sk_gso_max_segs: Maximum number of GSO segments
+ * @sk_sg_max_frags: Maximum number of SG fragments
* @sk_lingertime: %SO_LINGER l_linger setting
* @sk_backlog: always used with the per-socket spinlock held
* @sk_callback_lock: used with the callbacks in the end of this struct
@@ -456,6 +457,7 @@ struct sock {
int (*sk_backlog_rcv)(struct sock *sk,
struct sk_buff *skb);
void (*sk_destruct)(struct sock *sk);
+ u16 sk_sg_max_frags;
};
#define __sk_user_data(sk) ((*((void __rcu **)&(sk)->sk_user_data)))
diff --git a/net/core/dev.c b/net/core/dev.c
index ae00b89..abfbd3a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7106,6 +7106,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv,
const char *name,
dev->gso_max_size = GSO_MAX_SIZE;
dev->gso_max_segs = GSO_MAX_SEGS;
dev->gso_min_segs = 0;
+ dev->sg_max_frags = MAX_SKB_FRAGS;
INIT_LIST_HEAD(&dev->napi_list);
INIT_LIST_HEAD(&dev->unreg_list);
diff --git a/net/core/sock.c b/net/core/sock.c
index e31dfce..53d0cf0 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1621,6 +1621,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
}
}
sk->sk_gso_max_segs = max_segs;
+ sk->sk_sg_max_frags = dst->dev->sg_max_frags;
}
EXPORT_SYMBOL_GPL(sk_setup_caps);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c82cca1..ca5f7a0 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -938,7 +938,7 @@ new_segment:
i = skb_shinfo(skb)->nr_frags;
can_coalesce = skb_can_coalesce(skb, i, page, offset);
- if (!can_coalesce && i >= MAX_SKB_FRAGS) {
+ if (!can_coalesce && i >= sk->sk_sg_max_frags) {
tcp_mark_push(tp, skb);
goto new_segment;
}
@@ -1211,7 +1211,7 @@ new_segment:
if (!skb_can_coalesce(skb, i, pfrag->page,
pfrag->offset)) {
- if (i == MAX_SKB_FRAGS || !sg) {
+ if (i >= sk->sk_sg_max_frags || !sg) {
tcp_mark_push(tp, skb);
goto new_segment;
}
--
2.4.3
--
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