linux-kernel - Re: Aarch64 EXT4FS inode checksum failures - seems to be weak memory ordering issues

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Message-ID: <20210112132049.GA26096@wunner.de>
Date:   Tue, 12 Jan 2021 14:20:49 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnd Bergmann <arnd@...nel.org>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        linux-toolchains@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Theodore Ts'o <tytso@....edu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Aarch64 EXT4FS inode checksum failures - seems to be weak memory
 ordering issues

On Fri, Jan 08, 2021 at 12:02:53PM -0800, Linus Torvalds wrote:
> I appreciate Arnd pointing out "--std=gnu11", though. What are the
> actual relevant language improvements?
> 
> Variable declarations in for-loops is the only one I can think of. I
> think that would clean up some code (and some macros), but might not
> be compelling on its own.

Anonymous structs/unions.  I used to have a use case for that in
struct efi_dev_path in include/linux/efi.h, but Ard Biesheuvel
refactored it in a gnu89-compatible way for v5.7 with db8952e7094f.

[The above was copy-pasted from last time this discussion came up
in July 2020.  Back then, Kirill Shutemov likewise mentioned the
local variables in loops feature:
https://lore.kernel.org/lkml/20200710111724.m4jaci73pykalxys@wunner.de/
]

Thanks,

Lukas