From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE0E9330D3B; Wed, 25 Mar 2026 19:39:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774467600; cv=none; b=Ql9n7VrixanBSyguemPkD+b61sFZ0AugFAH9QAsRAN6L1xowOhUXgyWEsYJqclw3Tp4rkS6DGdGpyvGMNSSyf5uXDUxVq0hNVPTsuzlwGrCMYLroIdRGMePHjzrxPPLhoBy8/ukZ11cG62PvwseXw96BK42MdgEc8RSEjoO7qUU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774467600; c=relaxed/simple; bh=vgzmS++XGgEKBkb/yAjVP8Sp4H+rVjAZlzJWbYtNQ5k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=gw4kHJnU96JqfovIwNY5nBaNPBRAPi1QhLJ3S2iCoNwLbj8wSnjeaQtPpGR1ZQNVcS1TzQ2g79UVWSY+lQA5+GzwQ07o6iTrSDSV+YCpyyyFcUSW8nbxb+FWsh1ih9trQGSPWPe3ehWP/G9ODkd5n4EjRCtPLPUJbHV632K6H3s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DygY0E8w; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DygY0E8w" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86172C4CEF7; Wed, 25 Mar 2026 19:39:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774467599; bh=vgzmS++XGgEKBkb/yAjVP8Sp4H+rVjAZlzJWbYtNQ5k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DygY0E8wyP/P9Q9kZFKoknR4RxtR6GMi9PjYKJh3Sbc2gqAytguh48eGOTnsx3c56 Q2YVatKuDK+N4nU8v6AxKOfcBzhChhEI3Df1zCL0wcOyAKNQgEB7oAOxflILmausqP WOCeoLY2lmAchg2c7NGHGU4qpdmOxFI+jpbH1K0Ei46HKczGrbgGRBm1sI8nru20Vm WRYSdUfozTetH29mYvuSFOROlG1SXAHZGao0e1tIcm/PcakbXOz5jtLmbmhcaQDLw8 UHpO2j30RaryLjmXyqJNpFRWy5VPKjdg008B9pxWETSOv3xeW2U6bVqeyivRW/5e7y efVryfxsae7fQ== Date: Wed, 25 Mar 2026 12:39:54 -0700 From: Eric Biggers To: Christoph Hellwig Cc: Andrew Morton , Richard Henderson , Matt Turner , Magnus Lindholm , Russell King , Catalin Marinas , Will Deacon , Ard Biesheuvel , Huacai Chen , WANG Xuerui , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , "David S. Miller" , Andreas Larsson , Richard Weinberger , Anton Ivanov , Johannes Berg , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Herbert Xu , Dan Williams , Chris Mason , David Sterba , Arnd Bergmann , Song Liu , Yu Kuai , Li Nan , Theodore Ts'o , "Jason A. Donenfeld" , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-crypto@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-arch@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: cleanup the RAID5 XOR library v3 Message-ID: <20260325193954.GC2305@quark> References: <20260324062211.3216301-1-hch@lst.de> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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