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Merge branch 'net-netpoll-improve-skb-pool-management'

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Breno Leitao says:

====================
net: netpoll: Improve SKB pool management

The netpoll subsystem pre-allocates 32 SKBs in a pool for emergency use
during out-of-memory conditions. However, the current implementation has
several inefficiencies:

 * The SKB pool, once allocated, is never freed:
	 * Resources remain allocated even after netpoll users are removed
	 * Failed initialization can leave pool populated forever
 * The global pool design makes resource tracking difficult

This series addresses these issues through three patches:

Patch 1 ("net: netpoll: Individualize the skb pool"):
 - Replace global pool with per-user pools in netpoll struct

Patch 2 ("net: netpoll: flush skb pool during cleanup"):
- Properly free pool resources during netconsole cleanup

These changes improve resource management and make the code more
maintainable.  As a side benefit, the improved structure would allow
netpoll to be modularized if desired in the future.

v2: https://lore.kernel.org/20241107-skb_buffers_v2-v2-0-288c6264ba4f@debian.org
v1: https://lore.kernel.org/20241025142025.3558051-1-leitao@debian.org
====================

Link: https://patch.msgid.link/20241114-skb_buffers_v2-v3-0-9be9f52a8b69@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2024-11-15 16:25:39 -08:00
commit bf3c76b4c4
2 changed files with 27 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/netpoll.h
View File

@ -32,6 +32,7 @@ struct netpoll {
bool ipv6;
u16 local_port, remote_port;
u8 remote_mac[ETH_ALEN];
struct sk_buff_head skb_pool;
};
struct netpoll_info {

45
net/core/netpoll.c
View File

@ -45,9 +45,6 @@
#define MAX_UDP_CHUNK 1460
#define MAX_SKBS 32
static struct sk_buff_head skb_pool;
#define USEC_PER_POLL 50
#define MAX_SKB_SIZE \
@ -234,20 +231,23 @@ void netpoll_poll_enable(struct net_device *dev)
up(&ni->dev_lock);
}
static void refill_skbs(void)
static void refill_skbs(struct netpoll *np)
{
struct sk_buff_head *skb_pool;
struct sk_buff *skb;
unsigned long flags;
spin_lock_irqsave(&skb_pool.lock, flags);
while (skb_pool.qlen < MAX_SKBS) {
skb_pool = &np->skb_pool;
spin_lock_irqsave(&skb_pool->lock, flags);
while (skb_pool->qlen < MAX_SKBS) {
skb = alloc_skb(MAX_SKB_SIZE, GFP_ATOMIC);
if (!skb)
break;
__skb_queue_tail(&skb_pool, skb);
__skb_queue_tail(skb_pool, skb);
}
spin_unlock_irqrestore(&skb_pool.lock, flags);
spin_unlock_irqrestore(&skb_pool->lock, flags);
}
static void zap_completion_queue(void)
@ -284,12 +284,12 @@ static struct sk_buff *find_skb(struct netpoll *np, int len, int reserve)
struct sk_buff *skb;
zap_completion_queue();
refill_skbs();
refill_skbs(np);
repeat:
skb = alloc_skb(len, GFP_ATOMIC);
if (!skb)
skb = skb_dequeue(&skb_pool);
skb = skb_dequeue(&np->skb_pool);
if (!skb) {
if (++count < 10) {
@ -531,6 +531,14 @@ static int netpoll_parse_ip_addr(const char *str, union inet_addr *addr)
return -1;
}
static void skb_pool_flush(struct netpoll *np)
{
struct sk_buff_head *skb_pool;
skb_pool = &np->skb_pool;
skb_queue_purge_reason(skb_pool, SKB_CONSUMED);
}
int netpoll_parse_options(struct netpoll *np, char *opt)
{
char *cur=opt, *delim;
@ -673,6 +681,8 @@ int netpoll_setup(struct netpoll *np)
struct in_device *in_dev;
int err;
skb_queue_head_init(&np->skb_pool);
rtnl_lock();
if (np->dev_name[0]) {
struct net *net = current->nsproxy->net_ns;
@ -773,14 +783,16 @@ put_noaddr:
}
/* fill up the skb queue */
refill_skbs();
refill_skbs(np);
err = __netpoll_setup(np, ndev);
if (err)
goto put;
goto flush;
rtnl_unlock();
return 0;
flush:
skb_pool_flush(np);
put:
DEBUG_NET_WARN_ON_ONCE(np->dev);
if (ip_overwritten)
@ -792,13 +804,6 @@ unlock:
}
EXPORT_SYMBOL(netpoll_setup);
static int __init netpoll_init(void)
{
skb_queue_head_init(&skb_pool);
return 0;
}
core_initcall(netpoll_init);
static void rcu_cleanup_netpoll_info(struct rcu_head *rcu_head)
{
struct netpoll_info *npinfo =
@ -835,6 +840,8 @@ void __netpoll_cleanup(struct netpoll *np)
call_rcu(&npinfo->rcu, rcu_cleanup_netpoll_info);
} else
RCU_INIT_POINTER(np->dev->npinfo, NULL);
skb_pool_flush(np);
}
EXPORT_SYMBOL_GPL(__netpoll_cleanup);