linux-kernel - Re: riscv32 EXT4 splat, 6.8 regression?

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Message-ID: <Zh6urRin2-wVxNeq@casper.infradead.org>
Date: Tue, 16 Apr 2024 18:00:29 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Nam Cao <namcao@...utronix.de>,
	Björn Töpel <bjorn@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
	Andreas Dilger <adilger@...ger.ca>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Jan Kara <jack@...e.cz>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-riscv@...ts.infradead.org, Theodore Ts'o <tytso@....edu>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Conor Dooley <conor@...nel.org>,
	Anders Roxell <anders.roxell@...aro.org>,
	Alexandre Ghiti <alex@...ti.fr>
Subject: Re: riscv32 EXT4 splat, 6.8 regression?

On Tue, Apr 16, 2024 at 07:31:54PM +0300, Mike Rapoport wrote:
> > @@ -238,17 +237,9 @@ static void __init setup_bootmem(void)
> >  	/*
> >  	 * memblock allocator is not aware of the fact that last 4K bytes of
> >  	 * the addressable memory can not be mapped because of IS_ERR_VALUE
> > -	 * macro. Make sure that last 4k bytes are not usable by memblock
> > -	 * if end of dram is equal to maximum addressable memory.  For 64-bit
> > -	 * kernel, this problem can't happen here as the end of the virtual
> > -	 * address space is occupied by the kernel mapping then this check must
> > -	 * be done as soon as the kernel mapping base address is determined.
> > +	 * macro. Make sure that last 4k bytes are not usable by memblock.
> >  	 */
> 
> It's not only memblock, but buddy as well, so maybe
> 
> 	/*
> 	 * The last 4K bytes of the addressable memory can not be used
> 	 * because of IS_ERR_VALUE macro. Make sure that last 4K bytes are
> 	 * not usable by kernel memory allocators.
> 	 */
> 
> > -	if (!IS_ENABLED(CONFIG_64BIT)) {
> > -		max_mapped_addr = __pa(~(ulong)0);
> > -		if (max_mapped_addr == (phys_ram_end - 1))
> > -			memblock_set_current_limit(max_mapped_addr - 4096);
> > -	}
> > +	memblock_reserve(__pa(-PAGE_SIZE), PAGE_SIZE);
> 
> Ack.

Can this go to generic code instead of letting architecture maintainers
fall over it?