Re: [PATCH v2 net] tcp: use GFP_ATOMIC in tcp_send_active_reset()

[Matthieu Baerts <matttbe@kernel.org>]

Hi Eric,

On 27/08/2026 11:59, Eric Dumazet wrote:
> tcp_send_active_reset() can be called from contexts where gfp_any()
> (in tcp_disconnect()) or sk->sk_allocation (in __tcp_close() and
> mptcp_do_fastclose()) evaluates to GFP_KERNEL, which includes
> __GFP_FS and __GFP_DIRECT_RECLAIM.
> 
> Allocating with GFP_KERNEL while holding the socket lock (sk_lock) creates
> a lockdep dependency:
>   sk_lock -> fs_reclaim
> 
> This causes false-positive lockdep circular locking warnings with storage
> subsystems (such as nvme-tcp) that acquire socket locks in block I/O paths
> and invoke tcp_disconnect() or close sockets upon teardown:
>   set->srcu -> sk_lock -> fs_reclaim -> elevator_lock -> set->srcu
> 
> Active resets are small RST packet headers that should never
> enter direct reclaim or block while holding socket locks.
> 
> Use sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN) inside tcp_send_active_reset()
> and remove its priority argument. This preserves __GFP_MEMALLOC access
> for SOCK_MEMALLOC sockets, suppresses allocation failure warnings,
> and aligns with other control packet allocations (e.g. tcp_send_fin(),
> __tcp_send_ack(), tcp_xmit_probe_skb()).

Thank you for the modification! For the MPTCP part:

Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.