Merge branch 'bpf-lpm_trie-allow-sleepable-bpf-programs-to-use-lpm-tries'

Vlad Poenaru says:

====================
bpf, lpm_trie: Allow sleepable BPF programs to use LPM tries

trie_lookup_elem() annotates its rcu_dereference_check() walks with only
rcu_read_lock_bh_held(), so a sleepable BPF program that touches an LPM
trie (e.g. a sleepable LSM hook calling bpf_map_lookup_elem()) trips a
"suspicious RCU usage" lockdep splat on debug kernels: it holds only
rcu_read_lock_trace(), which that annotation does not accept.

Patch 1 relaxes the rcu_dereference annotations in the trie walks so they
no longer trip lockdep from the Tasks Trace context, including the
trie_update_elem()/trie_delete_elem() writer walks (protected by
trie->lock). Patch 2 adds BPF_MAP_TYPE_LPM_TRIE to the verifier's
sleepable map whitelist so sleepable programs can reference an LPM trie
directly, not just as the inner map of a map-of-maps. LPM trie nodes are
reclaimed via bpf_mem_cache_free_rcu(), which chains a regular RCU grace
period into a Tasks Trace grace period before freeing -- the same
discipline BPF_MAP_TYPE_HASH relies on for sleepable access.

Changes since v1:
- Split into a 2-patch series.
- Patch 1 now also converts the trie_update_elem()/trie_delete_elem()
  walks from rcu_dereference() to rcu_dereference_protected(*p, 1),
  addressing review feedback that v1 only fixed the lookup path and left
  the same splat on the writer paths.
- New patch 2 adds the verifier whitelist entry so the fix is actually
  reachable for directly-referenced LPM tries.
- Retitled v1 ("Allow lookups from sleepable BPF programs").

v1: https://lore.kernel.org/all/20260529174233.2954240-1-vlad.wing@gmail.com/
====================

Link: https://patch.msgid.link/20260609135558.193287-1-vlad.wing@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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