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Date: Wed, 12 Apr 2023 21:26:03 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org, edumazet@...gle.com, pabeni@...hat.com,
hawk@...nel.org, ilias.apalodimas@...aro.org,
linyunsheng@...wei.com, alexander.duyck@...il.com,
Jakub Kicinski <kuba@...nel.org>,
Tariq Toukan <tariqt@...dia.com>
Subject: [PATCH net-next v2 1/3] net: skb: plumb napi state thru skb freeing paths
We maintain a NAPI-local cache of skbs which is fed by napi_consume_skb().
Going forward we will also try to cache head and data pages.
Plumb the "are we in a normal NAPI context" information thru
deeper into the freeing path, up to skb_release_data() and
skb_free_head()/skb_pp_recycle(). The "not normal NAPI context"
comes from netpoll which passes budget of 0 to try to reap
the Tx completions but not perform any Rx.
Use "bool napi_safe" rather than bare "int budget",
the further we get from NAPI the more confusing the budget
argument may seem (particularly whether 0 or MAX is the
correct value to pass in when not in NAPI).
Reviewed-by: Tariq Toukan <tariqt@...dia.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
v2:
- clarify the budget 0 and fix the name of the argument in
the commit message
v1:
- feed the cache in __kfree_skb_defer(), it's in NAPI
- s/in_normal_napi/napi_safe/
---
net/core/skbuff.c | 38 ++++++++++++++++++++------------------
1 file changed, 20 insertions(+), 18 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 050a875d09c5..b2092166f7e2 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -839,7 +839,7 @@ static void skb_clone_fraglist(struct sk_buff *skb)
skb_get(list);
}
-static bool skb_pp_recycle(struct sk_buff *skb, void *data)
+static bool skb_pp_recycle(struct sk_buff *skb, void *data, bool napi_safe)
{
if (!IS_ENABLED(CONFIG_PAGE_POOL) || !skb->pp_recycle)
return false;
@@ -856,12 +856,12 @@ static void skb_kfree_head(void *head, unsigned int end_offset)
kfree(head);
}
-static void skb_free_head(struct sk_buff *skb)
+static void skb_free_head(struct sk_buff *skb, bool napi_safe)
{
unsigned char *head = skb->head;
if (skb->head_frag) {
- if (skb_pp_recycle(skb, head))
+ if (skb_pp_recycle(skb, head, napi_safe))
return;
skb_free_frag(head);
} else {
@@ -869,7 +869,8 @@ static void skb_free_head(struct sk_buff *skb)
}
}
-static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason)
+static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason,
+ bool napi_safe)
{
struct skb_shared_info *shinfo = skb_shinfo(skb);
int i;
@@ -894,7 +895,7 @@ static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason)
if (shinfo->frag_list)
kfree_skb_list_reason(shinfo->frag_list, reason);
- skb_free_head(skb);
+ skb_free_head(skb, napi_safe);
exit:
/* When we clone an SKB we copy the reycling bit. The pp_recycle
* bit is only set on the head though, so in order to avoid races
@@ -955,11 +956,12 @@ void skb_release_head_state(struct sk_buff *skb)
}
/* Free everything but the sk_buff shell. */
-static void skb_release_all(struct sk_buff *skb, enum skb_drop_reason reason)
+static void skb_release_all(struct sk_buff *skb, enum skb_drop_reason reason,
+ bool napi_safe)
{
skb_release_head_state(skb);
if (likely(skb->head))
- skb_release_data(skb, reason);
+ skb_release_data(skb, reason, napi_safe);
}
/**
@@ -973,7 +975,7 @@ static void skb_release_all(struct sk_buff *skb, enum skb_drop_reason reason)
void __kfree_skb(struct sk_buff *skb)
{
- skb_release_all(skb, SKB_DROP_REASON_NOT_SPECIFIED);
+ skb_release_all(skb, SKB_DROP_REASON_NOT_SPECIFIED, false);
kfree_skbmem(skb);
}
EXPORT_SYMBOL(__kfree_skb);
@@ -1027,7 +1029,7 @@ static void kfree_skb_add_bulk(struct sk_buff *skb,
return;
}
- skb_release_all(skb, reason);
+ skb_release_all(skb, reason, false);
sa->skb_array[sa->skb_count++] = skb;
if (unlikely(sa->skb_count == KFREE_SKB_BULK_SIZE)) {
@@ -1201,7 +1203,7 @@ EXPORT_SYMBOL(consume_skb);
void __consume_stateless_skb(struct sk_buff *skb)
{
trace_consume_skb(skb, __builtin_return_address(0));
- skb_release_data(skb, SKB_CONSUMED);
+ skb_release_data(skb, SKB_CONSUMED, false);
kfree_skbmem(skb);
}
@@ -1226,7 +1228,7 @@ static void napi_skb_cache_put(struct sk_buff *skb)
void __kfree_skb_defer(struct sk_buff *skb)
{
- skb_release_all(skb, SKB_DROP_REASON_NOT_SPECIFIED);
+ skb_release_all(skb, SKB_DROP_REASON_NOT_SPECIFIED, true);
napi_skb_cache_put(skb);
}
@@ -1264,7 +1266,7 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
return;
}
- skb_release_all(skb, SKB_CONSUMED);
+ skb_release_all(skb, SKB_CONSUMED, !!budget);
napi_skb_cache_put(skb);
}
EXPORT_SYMBOL(napi_consume_skb);
@@ -1395,7 +1397,7 @@ EXPORT_SYMBOL_GPL(alloc_skb_for_msg);
*/
struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src)
{
- skb_release_all(dst, SKB_CONSUMED);
+ skb_release_all(dst, SKB_CONSUMED, false);
return __skb_clone(dst, src);
}
EXPORT_SYMBOL_GPL(skb_morph);
@@ -2018,9 +2020,9 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
if (skb_has_frag_list(skb))
skb_clone_fraglist(skb);
- skb_release_data(skb, SKB_CONSUMED);
+ skb_release_data(skb, SKB_CONSUMED, false);
} else {
- skb_free_head(skb);
+ skb_free_head(skb, false);
}
off = (data + nhead) - skb->head;
@@ -6389,12 +6391,12 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
skb_frag_ref(skb, i);
if (skb_has_frag_list(skb))
skb_clone_fraglist(skb);
- skb_release_data(skb, SKB_CONSUMED);
+ skb_release_data(skb, SKB_CONSUMED, false);
} else {
/* we can reuse existing recount- all we did was
* relocate values
*/
- skb_free_head(skb);
+ skb_free_head(skb, false);
}
skb->head = data;
@@ -6529,7 +6531,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
skb_kfree_head(data, size);
return -ENOMEM;
}
- skb_release_data(skb, SKB_CONSUMED);
+ skb_release_data(skb, SKB_CONSUMED, false);
skb->head = data;
skb->head_frag = 0;
--
2.39.2
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