From: Eric Biggers <ebiggers@kernel•org>
To: Christoph Hellwig <hch@lst•de>
Cc: Andrew Morton <akpm@linux-foundation•org>,
Richard Henderson <richard.henderson@linaro•org>,
Matt Turner <mattst88@gmail•com>,
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linux-raid@vger•kernel.org
Subject: Re: cleanup the RAID5 XOR library v3
Date: Wed, 25 Mar 2026 12:39:54 -0700 [thread overview]
Message-ID: <20260325193954.GC2305@quark> (raw)
In-Reply-To: <20260324062211.3216301-1-hch@lst.de>
On Tue, Mar 24, 2026 at 07:21:36AM +0100, Christoph Hellwig wrote:
> Hi all,
>
> the XOR library used for the RAID5 parity is a bit of a mess right now.
> The main file sits in crypto/ despite not being cryptography and not
> using the crypto API, with the generic implementations sitting in
> include/asm-generic and the arch implementations sitting in an asm/
> header in theory. The latter doesn't work for many cases, so
> architectures often build the code directly into the core kernel, or
> create another module for the architecture code.
>
> Changes this to a single module in lib/ that also contains the
> architecture optimizations, similar to the library work Eric Biggers
> has done for the CRC and crypto libraries later. After that it changes
> to better calling conventions that allow for smarter architecture
> implementations (although none is contained here yet), and uses
> static_call to avoid indirection function call overhead.
>
> A git tree is also available here:
>
> git://git.infradead.org/users/hch/misc.git xor-improvements
>
> Gitweb:
>
> https://git.infradead.org/?p=users/hch/misc.git;a=shortlog;h=refs/heads/xor-improvements
This generally looks good, but yes, please check the comments from
https://sashiko.dev/#/patchset/20260324062211.3216301-1-hch@lst.de, as
Andrew mentioned.
The bug where the test generates length 0 is definitely real. I
verified it causes the test to crash on some platforms.
raid_run_ops() calling xor_gen() (indirectly) with preemption disabled
looks real as well, though I haven't tested it. If preemption is indeed
not the right thing to check, then I guess (following up from
https://lore.kernel.org/linux-crypto/20260303195517.GC2846@sol/) it
would need to be something like:
WARN_ON_ONCE(!in_task() || irqs_disabled() || softirq_count() != 0);
Ugly, but we're running out of options.
(This sort of thing is why the functions in lib/crypto/ and lib/crc/ are
just supported in all contexts instead. If FPU/vector/SIMD registers
cannot be used in the current context, then a scalar fallback is used.)
- Eric
next prev parent reply other threads:[~2026-03-25 19:40 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-24 6:21 cleanup the RAID5 XOR library v3 Christoph Hellwig
2026-03-24 6:21 ` [PATCH 01/26] xor: assert that xor_blocks is not from preemptible user context Christoph Hellwig
2026-03-24 6:21 ` [PATCH 02/26] arm/xor: remove in_interrupt() handling Christoph Hellwig
2026-03-24 6:21 ` [PATCH 03/26] um/xor: cleanup xor.h Christoph Hellwig
2026-03-24 6:21 ` [PATCH 04/26] xor: move to lib/raid/ Christoph Hellwig
2026-03-24 6:21 ` [PATCH 05/26] xor: small cleanups Christoph Hellwig
2026-03-24 6:21 ` [PATCH 06/26] xor: cleanup registration and probing Christoph Hellwig
2026-03-24 6:21 ` [PATCH 07/26] xor: split xor.h Christoph Hellwig
2026-03-24 6:21 ` [PATCH 08/26] xor: remove macro abuse for XOR implementation registrations Christoph Hellwig
2026-03-24 6:21 ` [PATCH 09/26] xor: move generic implementations out of asm-generic/xor.h Christoph Hellwig
2026-03-24 6:21 ` [PATCH 10/26] alpha: move the XOR code to lib/raid/ Christoph Hellwig
2026-03-24 6:21 ` [PATCH 11/26] arm: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 12/26] arm64: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 13/26] loongarch: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 14/26] powerpc: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 15/26] riscv: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 16/26] sparc: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 17/26] s390: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 18/26] x86: " Christoph Hellwig
2026-03-24 6:21 ` [PATCH 19/26] xor: avoid indirect calls for arm64-optimized ops Christoph Hellwig
2026-03-24 6:21 ` [PATCH 20/26] xor: make xor.ko self-contained in lib/raid/ Christoph Hellwig
2026-03-24 6:21 ` [PATCH 21/26] xor: add a better public API Christoph Hellwig
2026-03-24 6:21 ` [PATCH 22/26] async_xor: use xor_gen Christoph Hellwig
2026-03-24 6:21 ` [PATCH 23/26] btrfs: " Christoph Hellwig
2026-03-24 6:22 ` [PATCH 24/26] xor: pass the entire operation to the low-level ops Christoph Hellwig
2026-03-24 6:22 ` [PATCH 25/26] xor: use static_call for xor_gen Christoph Hellwig
2026-03-24 6:22 ` [PATCH 26/26] xor: add a kunit test case Christoph Hellwig
2026-03-24 12:59 ` cleanup the RAID5 XOR library v3 Andrew Morton
2026-03-24 16:42 ` Andrew Morton
2026-03-25 19:39 ` Eric Biggers [this message]
2026-03-26 5:18 ` Christoph Hellwig
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