[PATCH RFC 0/4] async_tx/md: Remove async_tx framework

[Frank . Li]

This RFC is collecting more feedbacks to device when is good time to remove
whole async_tx framework and how to remove it safely. And is overall
direction correction.

Little to no real hardware acceleration usage:
  Most systems run RAID5/6 parity calculations on the CPU using optimized
  XOR/PQ implementations, while DMAEngine-backed async_tx acceleration is
  rarely present or exercised.

Added abstraction and maintenance cost:
  async_tx introduces an extra layer between MD RAID and parity operations,
  making the code harder to understand, debug, and maintain.

Modern CPUs outperform DMA offload:
  SIMD implementations (SSE/AVX/NEON and architecture-specific RAID
  routines) often provide better performance than DMA descriptor setup and
  completion handling overhead.

Obsolete hardware dependencies:
  Many async_tx acceleration backends were designed for older DMA/XOR
  engines that are no longer common in contemporary systems.

Complex asynchronous execution model:
  Dependency chains, callback handling, and DMA transaction management
  increase code complexity without corresponding performance benefits on
  typical deployments.Simplifies RAID code paths: Removing async_tx allows
  direct use of synchronous XOR/PQ helpers, reducing indirection in raid5.c
  source code [linux/drivers/md/raid5.c].

Reduces testing burden:
  Eliminates rarely used code paths that are difficult to validate and more
  likely to accumulate latent bugs.

Aligns implementation with actual usage:
  The vast majority of MD RAID deployments already rely on software parity
  generation rather than DMA offload.

Current dmaengine support xor is

Driver File		Driver Name			First Added Date
==========================================================================
mv_xor.c		Marvell XOR Engine (mv_xor)	2008-07-08
ppc4xx/adma.c		ppc440spe ADMA (PPC4xx)		2009-12-11
fsl_raid.c		Freescale RAID Engine (fsl_re)	2015-03-03
xgene-dma.c		APM X-Gene DMA			2015-03-18
ioat/init.c		Intel IOAT DMA (ioatdma)	2015-08-11
mv_xor_v2.c		Marvell XOR Engine v2		2016-06-16
bcm-sba-raid.c		BCM SBA RAID (Broadcom)		2017-05-15

fsl_raid is for power pc SoC, which already EOF.

Patches is build test only now.

To: Alasdair Kergon <agk@xxxxxxxxxx>
To: Mike Snitzer <snitzer@xxxxxxxxxx>
To: Mikulas Patocka <mpatocka@xxxxxxxxxx>
To: Benjamin Marzinski <bmarzins@xxxxxxxxxx>
To: Song Liu <song@xxxxxxxxxx>
To: Yu Kuai <yukuai@xxxxxxx>
To: Li Nan <magiclinan@xxxxxxxxxxxxxx>
To: Xiao Ni <xiao@xxxxxxxxxx>
To: Dan Williams <djbw@xxxxxxxxxx>
To: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
To: "David S. Miller" <davem@xxxxxxxxxxxxx>
To: Jonathan Corbet <corbet@xxxxxxx>
To: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
To: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: dm-devel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: linux-raid@xxxxxxxxxxxxxxx
Cc: linux-crypto@xxxxxxxxxxxxxxx
Cc: linux-doc@xxxxxxxxxxxxxxx
Cc: Anatolij Gustschin <agust@xxxxxxx>
Cc: Saeed Bishara <saeed@xxxxxxxxxxx>
Cc: Rameshwar Prasad Sahu <rsahu@xxxxxxx>
Cc: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
Cc: Anup Patel <anup.patel@xxxxxxxxxxxx>

Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
---
Frank Li (4):
      md/dm-integrity: replace async_tx with synchronous xor for journal
      md/raid5-ppl: replace async_tx with synchronous xor
      md/raid5: replace async_tx with synchronous xor/pq operations
      crypto: remove async_tx framework

 Documentation/crypto/async-tx-api.rst | 270 ---------------
 Documentation/crypto/index.rst        |   1 -
 crypto/Kconfig                        |   5 -
 crypto/Makefile                       |   4 -
 crypto/async_tx/Kconfig               |  28 --
 crypto/async_tx/Makefile              |   7 -
 crypto/async_tx/async_memcpy.c        |  97 ------
 crypto/async_tx/async_pq.c            | 464 --------------------------
 crypto/async_tx/async_raid6_recov.c   | 595 ----------------------------------
 crypto/async_tx/async_tx.c            | 299 -----------------
 crypto/async_tx/async_xor.c           | 380 ----------------------
 crypto/async_tx/raid6test.c           | 250 --------------
 drivers/md/dm-integrity.c             |  26 +-
 drivers/md/raid5-log.h                |   4 +-
 drivers/md/raid5-ppl.c                |  40 +--
 drivers/md/raid5.c                    | 467 +++++++++++++-------------
 include/linux/async_tx.h              | 187 -----------
 17 files changed, 281 insertions(+), 2843 deletions(-)
---
base-commit: 98a4f6276df67a1bb37b1be56a3ab4285155e3df
change-id: 20261015-asycn_tx_remove-381cd003d9f7

Best regards,
--  
Frank Li <Frank.Li@xxxxxxx>