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Date: Thu, 22 Aug 2019 13:24:14 +0100
From: David Howells <dhowells@...hat.com>
To: netdev@...r.kernel.org
Cc: dhowells@...hat.com, linux-afs@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: [PATCH net 7/9] rxrpc: Add a shadow refcount in the skb private data
Add a shadow refcount to count pins from the Rx/Tx ring on an sk_buff so
that we can hold multiple refs on it without causing skb_cow_data() to
throw an assertion.
This is stored in the private part of the sk_buff as laid out in struct
rxrpc_skb_priv.
Add two accessor functions for pinning (adding) or unpinning (discarding) a
shadow ref.
Signed-off-by: David Howells <dhowells@...hat.com>
---
include/trace/events/rxrpc.h | 15 ++++++++---
net/rxrpc/ar-internal.h | 2 +
net/rxrpc/skbuff.c | 57 ++++++++++++++++++++++++++++++++++++++----
3 files changed, 65 insertions(+), 9 deletions(-)
diff --git a/include/trace/events/rxrpc.h b/include/trace/events/rxrpc.h
index e2356c51883b..34237ea8ceb0 100644
--- a/include/trace/events/rxrpc.h
+++ b/include/trace/events/rxrpc.h
@@ -28,10 +28,12 @@ enum rxrpc_skb_trace {
rxrpc_skb_got,
rxrpc_skb_lost,
rxrpc_skb_new,
+ rxrpc_skb_pin,
rxrpc_skb_purged,
rxrpc_skb_received,
rxrpc_skb_rotated,
rxrpc_skb_seen,
+ rxrpc_skb_unpin,
};
enum rxrpc_local_trace {
@@ -228,10 +230,12 @@ enum rxrpc_tx_point {
EM(rxrpc_skb_got, "GOT") \
EM(rxrpc_skb_lost, "*L*") \
EM(rxrpc_skb_new, "NEW") \
+ EM(rxrpc_skb_pin, "PIN") \
EM(rxrpc_skb_purged, "PUR") \
EM(rxrpc_skb_received, "RCV") \
EM(rxrpc_skb_rotated, "ROT") \
- E_(rxrpc_skb_seen, "SEE")
+ EM(rxrpc_skb_seen, "SEE") \
+ E_(rxrpc_skb_unpin, "UPN")
#define rxrpc_local_traces \
EM(rxrpc_local_got, "GOT") \
@@ -633,14 +637,15 @@ TRACE_EVENT(rxrpc_call,
TRACE_EVENT(rxrpc_skb,
TP_PROTO(struct sk_buff *skb, enum rxrpc_skb_trace op,
- int usage, int mod_count, const void *where),
+ int usage, int mod_count, int pins, const void *where),
- TP_ARGS(skb, op, usage, mod_count, where),
+ TP_ARGS(skb, op, usage, mod_count, pins, where),
TP_STRUCT__entry(
__field(struct sk_buff *, skb )
__field(enum rxrpc_skb_trace, op )
__field(u8, flags )
+ __field(u8, pins )
__field(int, usage )
__field(int, mod_count )
__field(const void *, where )
@@ -651,16 +656,18 @@ TRACE_EVENT(rxrpc_skb,
__entry->flags = rxrpc_skb(skb)->rx_flags;
__entry->op = op;
__entry->usage = usage;
+ __entry->pins = pins;
__entry->mod_count = mod_count;
__entry->where = where;
),
- TP_printk("s=%p %cx %s u=%d m=%d p=%pSR",
+ TP_printk("s=%p %cx %s u=%d m=%d r=%u p=%pSR",
__entry->skb,
__entry->flags & RXRPC_SKB_TX_BUFFER ? 'T' : 'R',
__print_symbolic(__entry->op, rxrpc_skb_traces),
__entry->usage,
__entry->mod_count,
+ __entry->pins,
__entry->where)
);
diff --git a/net/rxrpc/ar-internal.h b/net/rxrpc/ar-internal.h
index 2d5294f3e62f..d784d58e0a0d 100644
--- a/net/rxrpc/ar-internal.h
+++ b/net/rxrpc/ar-internal.h
@@ -1113,6 +1113,8 @@ void rxrpc_see_skb(struct sk_buff *, enum rxrpc_skb_trace);
void rxrpc_get_skb(struct sk_buff *, enum rxrpc_skb_trace);
void rxrpc_free_skb(struct sk_buff *, enum rxrpc_skb_trace);
void rxrpc_purge_queue(struct sk_buff_head *);
+void rxrpc_pin_skb(struct sk_buff *, enum rxrpc_skb_trace);
+void rxrpc_unpin_skb(struct sk_buff *, enum rxrpc_skb_trace);
/*
* sysctl.c
diff --git a/net/rxrpc/skbuff.c b/net/rxrpc/skbuff.c
index 8e6f45f84b9b..f9986a1510d3 100644
--- a/net/rxrpc/skbuff.c
+++ b/net/rxrpc/skbuff.c
@@ -22,9 +22,12 @@
*/
void rxrpc_new_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
{
+ struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
const void *here = __builtin_return_address(0);
int n = atomic_inc_return(select_skb_count(skb));
- trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
+
+ atomic_set(&sp->nr_ring_pins, 1);
+ trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, 1, here);
}
/*
@@ -33,9 +36,12 @@ void rxrpc_new_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
void rxrpc_see_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
{
const void *here = __builtin_return_address(0);
+
if (skb) {
+ struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
int n = atomic_read(select_skb_count(skb));
- trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
+ trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n,
+ atomic_read(&sp->nr_ring_pins), here);
}
}
@@ -44,9 +50,11 @@ void rxrpc_see_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
*/
void rxrpc_get_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
{
+ struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
const void *here = __builtin_return_address(0);
int n = atomic_inc_return(select_skb_count(skb));
- trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
+ trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n,
+ atomic_read(&sp->nr_ring_pins), here);
skb_get(skb);
}
@@ -56,11 +64,14 @@ void rxrpc_get_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
void rxrpc_free_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
{
const void *here = __builtin_return_address(0);
+
if (skb) {
+ struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
int n;
CHECK_SLAB_OKAY(&skb->users);
n = atomic_dec_return(select_skb_count(skb));
- trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, here);
+ trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n,
+ atomic_read(&sp->nr_ring_pins), here);
kfree_skb(skb);
}
}
@@ -72,10 +83,46 @@ void rxrpc_purge_queue(struct sk_buff_head *list)
{
const void *here = __builtin_return_address(0);
struct sk_buff *skb;
+
while ((skb = skb_dequeue((list))) != NULL) {
+ struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
int n = atomic_dec_return(select_skb_count(skb));
trace_rxrpc_skb(skb, rxrpc_skb_purged,
- refcount_read(&skb->users), n, here);
+ refcount_read(&skb->users), n,
+ atomic_read(&sp->nr_ring_pins), here);
kfree_skb(skb);
}
}
+
+/*
+ * Add a secondary ref on the socket buffer.
+ */
+void rxrpc_pin_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
+{
+ struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+ const void *here = __builtin_return_address(0);
+ int n = atomic_read(select_skb_count(skb));
+ int np;
+
+ np = atomic_inc_return(&sp->nr_ring_pins);
+ trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, np, here);
+}
+
+/*
+ * Remove a secondary ref on the socket buffer.
+ */
+void rxrpc_unpin_skb(struct sk_buff *skb, enum rxrpc_skb_trace op)
+{
+ const void *here = __builtin_return_address(0);
+
+ if (skb) {
+ struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+ int n = atomic_read(select_skb_count(skb));
+ int np;
+
+ np = atomic_dec_return(&sp->nr_ring_pins);
+ trace_rxrpc_skb(skb, op, refcount_read(&skb->users), n, np, here);
+ if (np == 0)
+ rxrpc_free_skb(skb, op);
+ }
+}
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