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Date: Tue, 16 Apr 2024 18:19:44 +0200
From: Nam Cao <namcao@linutronix.de>
To: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>, Christian Brauner <brauner@kernel.org>,
 Andreas Dilger <adilger@dilger.ca>, Al Viro <viro@zeniv.linux.org.uk>,
 linux-fsdevel <linux-fsdevel@vger.kernel.org>, Jan Kara <jack@suse.cz>,
 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
 linux-riscv@lists.infradead.org, Theodore Ts'o <tytso@mit.edu>, Ext4
 Developers List <linux-ext4@vger.kernel.org>, Conor Dooley
 <conor@kernel.org>, "Matthew Wilcox (Oracle)" <willy@infradead.org>, Anders
 Roxell <anders.roxell@linaro.org>, Alexandre Ghiti <alex@ghiti.fr>
Subject: Re: riscv32 EXT4 splat, 6.8 regression?
Message-ID: <20240416181944.23af44ee@namcao>
In-Reply-To: <87v84h2tee.fsf@all.your.base.are.belong.to.us>
References: <20240416-deppen-gasleitung-8098fcfd6bbd@brauner>
	<8734rlo9j7.fsf@all.your.base.are.belong.to.us>
	<Zh6KNglOu8mpTPHE@kernel.org>
	<20240416171713.7d76fe7d@namcao>
	<20240416173030.257f0807@namcao>
	<87v84h2tee.fsf@all.your.base.are.belong.to.us>
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On 2024-04-16 Bj=C3=B6rn T=C3=B6pel wrote:
> Nam Cao <namcao@linutronix.de> writes:
>=20
> > Fixed version:
> >
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index fa34cf55037b..af4192bc51d0 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -245,6 +245,7 @@ static void __init setup_bootmem(void)
> >  	 * be done as soon as the kernel mapping base address is determined.
> >  	 */
> >  	if (!IS_ENABLED(CONFIG_64BIT)) {
> > +		memblock_reserve(__pa(-PAGE_SIZE), PAGE_SIZE);
> >  		max_mapped_addr =3D __pa(~(ulong)0);
> >  		if (max_mapped_addr =3D=3D (phys_ram_end - 1))
> >  			memblock_set_current_limit(max_mapped_addr - 4096); =20
>=20
> Nice!
>=20
> Can't we get rid of the if-statement, and max_mapped_address as well?

I don't see why not :D

Best regards,
Nam

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index fa34cf55037b..f600cfee0aef 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -197,7 +197,6 @@ early_param("mem", early_mem);
 static void __init setup_bootmem(void)
 {
 	phys_addr_t vmlinux_end =3D __pa_symbol(&_end);
-	phys_addr_t max_mapped_addr;
 	phys_addr_t phys_ram_end, vmlinux_start;
=20
 	if (IS_ENABLED(CONFIG_XIP_KERNEL))
@@ -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.
 	 */
-	if (!IS_ENABLED(CONFIG_64BIT)) {
-		max_mapped_addr =3D __pa(~(ulong)0);
-		if (max_mapped_addr =3D=3D (phys_ram_end - 1))
-			memblock_set_current_limit(max_mapped_addr - 4096);
-	}
+	memblock_reserve(__pa(-PAGE_SIZE), PAGE_SIZE);
=20
 	min_low_pfn =3D PFN_UP(phys_ram_base);
 	max_low_pfn =3D max_pfn =3D PFN_DOWN(phys_ram_end);