[PATCH 0/7] netpoll: Untangle netpoll and netconsole

[Breno Leitao <leitao@debian.org>]

This patch series refactors the netpoll and netconsole subsystems to achieve
better separation of concerns and improved code modularity. The main goal is
to move netconsole-specific functionality out of the generic netpoll core,
making netpoll a cleaner, more focused transmission-only interface.

Current problems:
   * SKB pool is only used by netconsole, but, available in all netpoll
     instances, wasting memory.
   * Given, netpoll populates the SKB and send the package for
     netconsole, there is no way to have a fine grained lock, to protect
     only the SKB population (specifically the netconsole target ->buf).
   * In the future (when netconsole supports nbcon), the SKB will be
     populated and the TX deferred, which is impossible in the current
     configuration.

Key architectural changes:

1. SKB Pool Management Migration: Move all SKB pool management from netpoll
   core to netconsole driver, since netconsole is the sole user of this
   functionality. This reduces memory overhead for other netpoll users.

2. UDP Packet Construction Separation: Move UDP/IP packet preparation logic
   from netpoll to netconsole, making netpoll purely SKB transmission-focused.

3. Function Splitting: Split netpoll_send_udp() into separate preparation
   (netpoll_prepare_skb) and transmission (netpoll_send_skb) operations for
   better modularity and locking strategies.

4. Cleanup Consolidation: Move netpoll_cleanup() implementation to
   netconsole since it's the only caller, centralizing cleanup logic.

5. Enable netconsole to support nbcon, as being discussed in [1].
  * I have a PoC[2] for migrating netconsole to nbcon, which depends on
    this chage.

The series maintains full backward compatibility, and shouldn't have any
visible change for the user.

Link: https://lore.kernel.org/all/tgp5ddd2xdcvmkrhsyf2r6iav5a6ksvxk66xdw6ghur5g5ggee@cuz2o53younx/ [1]
Link: https://lore.kernel.org/all/b2qps3uywhmjaym4mht2wpxul4yqtuuayeoq4iv4k3zf5wdgh3@tocu6c7mj4lt/ [2]

To: Andrew Lunn <andrew+netdev@lunn.ch>
To: "David S. Miller" <davem@davemloft.net>
To: Eric Dumazet <edumazet@google.com>
To: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
To: Simon Horman <horms@kernel.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Clark Williams <clrkwllms@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-rt-devel@lists.linux.dev
Cc: kernel-team@meta.com
Cc: efault@gmx.de
Cc: calvin@wbinvd.org

Signed-off-by: Breno Leitao <leitao@debian.org>
---
Breno Leitao (7):
      netconsole: Split UDP message building and sending operations
      netpoll: move prepare skb functions to netconsole
      netpoll: Move netpoll_cleanup implementation to netconsole
      netpoll: Export zap_completion_queue
      netpoll: Move SKBs pool to netconsole side
      netpoll: Move find_skb() to netconsole and make it static
      netpoll: Flush skb_pool as part of netconsole cleanup

 drivers/net/netconsole.c | 273 +++++++++++++++++++++++++++++++++++++++++++++--
 include/linux/netpoll.h  |   2 +-
 net/core/netpoll.c       | 248 +-----------------------------------------
 3 files changed, 268 insertions(+), 255 deletions(-)
---
base-commit: 2fd4161d0d2547650d9559d57fc67b4e0a26a9e3
change-id: 20250902-netpoll_untangle_v3-e9f41781334e

Best regards,
--  
Breno Leitao <leitao@debian.org>