[PATCH net-next 1/2] nexthop: Restart nexthop dump based on last dumped nexthop identifier

[Ido Schimmel]

From: Ido Schimmel <ido...@nvidia.com>

Currently, a multi-part nexthop dump is restarted based on the number of
nexthops that have been dumped so far. This can result in a lot of
nexthops not being dumped when nexthops are simultaneously deleted:

 # ip nexthop | wc -l
 65536
 # ip nexthop flush
 Dump was interrupted and may be inconsistent.
 Flushed 36040 nexthops
 # ip nexthop | wc -l
 29496

Instead, restart the dump based on the nexthop identifier (fixed number)
of the last successfully dumped nexthop:

 # ip nexthop | wc -l
 65536
 # ip nexthop flush
 Dump was interrupted and may be inconsistent.
 Flushed 65536 nexthops
 # ip nexthop | wc -l
 0

Reported-by: Maksym Yaremchuk <maks...@nvidia.com>
Tested-by: Maksym Yaremchuk <maks...@nvidia.com>
Signed-off-by: Ido Schimmel <ido...@nvidia.com>
Reviewed-by: Petr Machata <pe...@nvidia.com>
---
 net/ipv4/nexthop.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
index 5a2fc8798d20..4075230b14c6 100644
--- a/net/ipv4/nexthop.c
+++ b/net/ipv4/nexthop.c
@@ -3140,26 +3140,24 @@ static int rtm_dump_walk_nexthops(struct sk_buff *skb,
                                  void *data)
 {
        struct rb_node *node;
-       int idx = 0, s_idx;
+       int s_idx;
        int err;
 
        s_idx = ctx->idx;
        for (node = rb_first(root); node; node = rb_next(node)) {
                struct nexthop *nh;
 
-               if (idx < s_idx)
-                       goto cont;
-
                nh = rb_entry(node, struct nexthop, rb_node);
-               ctx->idx = idx;
+               if (nh->id < s_idx)
+                       continue;
+
+               ctx->idx = nh->id;
                err = nh_cb(skb, cb, nh, data);
                if (err)
                        return err;
-cont:
-               idx++;
        }
 
-       ctx->idx = idx;
+       ctx->idx++;
        return 0;
 }
 
-- 
2.30.2