bpf: Implement iteration ops for resizable hashtab

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Implement get_next_key, batch lookup/lookup-and-delete, for_each_map_elem
callback, and the seq_file BPF iterator for BPF_MAP_TYPE_RHASH.

get_next_key() and batch use rhashtable_next_key() — stateless,
matches the syscall UAPI shape (no kernel-side iterator state).
get_next_key falls back to the first key when prev_key was
concurrently deleted (matches htab semantics). Batch reports
cursor loss as -EAGAIN so userspace can distinguish it from
end-of-iteration (-ENOENT) and restart from NULL.

The seq_file BPF iterator uses rhashtable_walk_* instead. It runs
only from read() syscall context, so the walker's spin_lock is
safe, and seq_file's per-fd state lets the walker handle rehash
correctly (retry on -EAGAIN) for stronger coverage than the
stateless API can provide.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20260605-rhash-v7-5-5b8e05f8630d@meta.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Mykyta Yatsenko 2026-06-05 04:41:22 -07:00 • committed by Alexei Starovoitov

parent 16b4d3e2fb

commit 818e008482

2 changed files with 348 additions and 2 deletions

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347

kernel/bpf/hashtab.c

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3

kernel/bpf/map_iter.c

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