net: devmem: replace gen_pool with freelist

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devmem only needs fixed-size net_iov allocations for each dma-buf binding.
The gen_pool tracks the same free set indirectly through DMA addresses,
which makes devmem depend on the generic allocator even though the users
are fixed-size net_iov chunks.

Mirror the io_uring zcrx model more closely by keeping a binding-level
freelist protected by spin_lock_bh(). Use a single net_iov_area owner for
the binding, populate each net_iov's DMA address while walking the SG
table, and check at teardown that all net_iovs have returned to the
freelist.

Validate the DMA-BUF size against the net_iov size up front and derive the
RX and TX entry count from it, avoiding a separate SG-table pass.

Drop the NET_DEVMEM select of GENERIC_ALLOCATOR now that devmem no longer
calls gen_pool APIs.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20260917181116.3319017-2-sdf@fomichev.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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This commit is contained in:

Stanislav Fomichev 2026-09-17 11:11:14 -07:00 • committed by Jakub Kicinski

parent cd7e4b1e47

commit 083e64a3af

3 changed files with 88 additions and 110 deletions

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1

net/Kconfig

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186

net/core/devmem.c

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15

net/core/devmem.h

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