[PATCH v2 5/6] mips: mm: add slab availability checking in ioremap_prot

From: Serge Semin <fancer.lancer@gmail.com>
To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Serge Semin <fancer.lancer@gmail.com>,
	Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
	Arnd Bergmann <arnd@arndb.de>,
	Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>,
	Aleksandar Rikalo <arikalo@gmail.com>,
	Dragan Mladjenovic <dragan.mladjenovic@syrmia.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Baoquan He <bhe@redhat.com>, Chao-ying Fu <cfu@wavecomp.com>,
	Yinglu Yang <yangyinglu@loongson.cn>,
	Tiezhu Yang <yangtiezhu@loongson.cn>,
	Mike Rapoport <rppt@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Marc Zyngier <maz@kernel.org>,
	linux-mips@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v2 5/6] mips: mm: add slab availability checking in ioremap_prot
Date: Sat,  2 Dec 2023 14:14:22 +0300	[thread overview]
Message-ID: <20231202111430.18059-6-fancer.lancer@gmail.com> (raw)
In-Reply-To: <20231202111430.18059-1-fancer.lancer@gmail.com>

Recent commit a5f616483110 ("mm/ioremap: add slab availability checking in
ioremap_prot") added the slab availability check to the generic
ioremap_prot() implementation. It is reasonable to be done for the
MIPS32-specific method too since it also relies on the
get_vm_area_caller() function (by means of get_vm_area()) which requires
the slab allocator being up and running before being called.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
---
 arch/mips/mm/ioremap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/mips/mm/ioremap.c b/arch/mips/mm/ioremap.c
index b6dad2fd5575..d8243d61ef32 100644
--- a/arch/mips/mm/ioremap.c
+++ b/arch/mips/mm/ioremap.c
@@ -72,6 +72,10 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, unsigned long size,
 	    flags == _CACHE_UNCACHED)
 		return (void __iomem *) CKSEG1ADDR(phys_addr);
 
+	/* Early remaps should use the unmapped regions til' VM is available */
+	if (WARN_ON_ONCE(!slab_is_available()))
+		return NULL;
+
 	/*
 	 * Don't allow anybody to remap RAM that may be allocated by the page
 	 * allocator, since that could lead to races & data clobbering.
-- 
2.42.1

