netdev - [PATCH v3 0/2] net: io_uring/zcrx: call netdev_queue_get_dma

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Message-ID: <20251101022449.1112313-1-dw@davidwei.uk>
Date: Fri, 31 Oct 2025 19:24:47 -0700
From: David Wei <dw@...idwei.uk>
To: io-uring@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Jens Axboe <axboe@...nel.dk>,
	Pavel Begunkov <asml.silence@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>
Subject: [PATCH v3 0/2] net: io_uring/zcrx: call netdev_queue_get_dma_dev() under instance lock

netdev ops must be called under instance lock or rtnl_lock, but
io_register_zcrx_ifq() isn't doing this for netdev_queue_get_dma_dev().
Fix this by taking the instance lock using netdev_get_by_index_lock().

netdev_get_by_index_lock() isn't available outside net/ by default, so
the first patch is a prep patch to export this under linux/netdevice.h.

Extended the instance lock section to include attaching a memory
provider. Could not move io_zcrx_create_area() outside, since the dmabuf
codepath IORING_ZCRX_AREA_DMABUF requires ifq->dev.

The netdev instance lock is taken first, followed by holding a ref. On
err, this is freed in LIFO order: put ref then unlock. After
successfully opening the mp on an rxq, the instance lock is unlocked and
ifq->if_rxq is set to a valid value. If there are future errs,
io_zcrx_ifq_free() will put the ref.

v3:
 - do not export netdev_get_by_index_lock()
 - fix netdev lock/ref cleanup

v2:
 - add Fixes tag
 - export netdev_get_by_index_lock()
 - use netdev_get_by_index_lock() + netdev_hold()
 - extend lock section to include net_mp_open_rxq()

David Wei (2):
  net: export netdev_get_by_index_lock()
  net: io_uring/zcrx: call netdev_queue_get_dma_dev() under instance
    lock

 include/linux/netdevice.h |  1 +
 io_uring/zcrx.c           | 16 ++++++++++------
 net/core/dev.h            |  1 -
 3 files changed, 11 insertions(+), 7 deletions(-)

-- 
2.47.3