Re: [PATCH] net: mediatek: fix PPE resource leak on remove

[Wayen Yan <win847@gmail.com>]

Hi Guangshuo,

Thanks for the patch. Calling mtk_ppe_deinit() from the remove path is
the right direction, since the probe error path already tears PPE down
but the successful remove path currently does not.

However, I think the cleanup is still incomplete.

mtk_ppe_deinit() currently only destroys the per-PPE l2_flows
rhashtable:

    rhashtable_destroy(&eth->ppe[i]->l2_flows);

This only destroys the hash table itself. It does not free any entries
that may still be stored in it. In this driver, L2 offload entries are
struct mtk_flow_entry objects allocated by mtk_flow_offload_replace()
and inserted into eth->flow_table, and bridge/L2 entries are also
indexed from ppe->l2_flows via mtk_foe_entry_commit_l2().

There is also a lifetime mismatch for eth->flow_table:
mtk_eth_offload_init() initializes it, but I do not see a matching
destroy/free on the remove path.

So I think remove should first drain the offload flow entries, using the
same per-entry teardown as mtk_flow_offload_destroy():

    mtk_foe_entry_clear(...)
    mtk_wed_flow_remove(...) when needed
    kfree(entry)

and then destroy eth->flow_table and the per-PPE l2_flows tables.
rhashtable_free_and_destroy() with a small callback would probably fit
this better than plain rhashtable_destroy().

While touching mtk_ppe_deinit(), it would also be better to use continue
instead of return for missing PPE instances, so later PPE instances are
not skipped.

One more minor cleanup issue: mtk_ppe_debugfs_init() creates the ppe%d
debugfs directory, but the PPE teardown path does not remove it.

So I agree with the fix direction, but I think this should be respun as
a complete PPE/offload cleanup rather than only adding mtk_ppe_deinit()
to mtk_remove().

Thanks,
Wayen