[PATCH net-next] net: add LINUX_MIB_PFMEMALLOCDROP counter

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

Debugging issues caused by pfmemalloc is often tedious.

Add a new SNMP counter to more easily diagnose these problems.

Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Josef Bacik <jba...@fb.com>
---
 include/uapi/linux/snmp.h |    1 +
 net/core/filter.c         |    5 +++--
 net/ipv4/proc.c           |    1 +
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 
e7a31f8306903f53bc5881ae4c271f85cad2e361..3b2bed7ca9a4d92c5671e614f2bc598668805f75
 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -240,6 +240,7 @@ enum
        LINUX_MIB_SACKMERGED,
        LINUX_MIB_SACKSHIFTFALLBACK,
        LINUX_MIB_TCPBACKLOGDROP,
+       LINUX_MIB_PFMEMALLOCDROP,
        LINUX_MIB_TCPMINTTLDROP, /* RFC 5082 */
        LINUX_MIB_TCPDEFERACCEPTDROP,
        LINUX_MIB_IPRPFILTER, /* IP Reverse Path Filter (rp_filter) */
diff --git a/net/core/filter.c b/net/core/filter.c
index 
1e00737e3bc370bc6c1afaf602439c81208ea3ac..0b753cbb2536763de53d266c9b9126d63942d7e5
 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -76,9 +76,10 @@ int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, 
unsigned int cap)
         * allow SOCK_MEMALLOC sockets to use it as this socket is
         * helping free memory
         */
-       if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC))
+       if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC)) {
+               NET_INC_STATS(sock_net(sk), LINUX_MIB_PFMEMALLOCDROP);
                return -ENOMEM;
-
+       }
        err = BPF_CGROUP_RUN_PROG_INET_INGRESS(sk, skb);
        if (err)
                return err;
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 
a9deeb90dd36e0a8f94596b4f563ad63925344cf..69cf49e8356d0184f774840c9dc96560f2ae2f2b
 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -262,6 +262,7 @@ static const struct snmp_mib snmp4_net_list[] = {
        SNMP_MIB_ITEM("TCPSackMerged", LINUX_MIB_SACKMERGED),
        SNMP_MIB_ITEM("TCPSackShiftFallback", LINUX_MIB_SACKSHIFTFALLBACK),
        SNMP_MIB_ITEM("TCPBacklogDrop", LINUX_MIB_TCPBACKLOGDROP),
+       SNMP_MIB_ITEM("PFMemallocDrop", LINUX_MIB_PFMEMALLOCDROP),
        SNMP_MIB_ITEM("TCPMinTTLDrop", LINUX_MIB_TCPMINTTLDROP),
        SNMP_MIB_ITEM("TCPDeferAcceptDrop", LINUX_MIB_TCPDEFERACCEPTDROP),
        SNMP_MIB_ITEM("IPReversePathFilter", LINUX_MIB_IPRPFILTER),