linux-kernel - [PATCH v1 5/9] s390/vmemmap: take the vmem

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Date:   Fri,  3 Jul 2020 15:39:13 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-s390@...r.kernel.org, linux-mm@...ck.org,
        David Hildenbrand <david@...hat.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>
Subject: [PATCH v1 5/9] s390/vmemmap: take the vmem_mutex when populating/freeing

Let's synchronize all accesses to the 1:1 and vmemmap mappings. This will
be especially relevant when wanting to cleanup empty page tables that could
be shared by both. Avoid races when removing tables that might be just
about to get reused.

Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Vasily Gorbik <gor@...ux.ibm.com>
Cc: Christian Borntraeger <borntraeger@...ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@...ibm.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 arch/s390/mm/vmem.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index bcddabd509da8..aa968f67d7f9f 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -293,6 +293,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 	pte_t *pt_dir;
 	int ret = -ENOMEM;
 
+	mutex_lock(&vmem_mutex);
 	pgt_prot = pgprot_val(PAGE_KERNEL);
 	sgt_prot = pgprot_val(SEGMENT_KERNEL);
 	if (!MACHINE_HAS_NX) {
@@ -364,6 +365,7 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 	}
 	ret = 0;
 out:
+	mutex_unlock(&vmem_mutex);
 	if (ret)
 		vmemmap_free(start, end, altmap);
 	return ret;
@@ -372,7 +374,9 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 void vmemmap_free(unsigned long start, unsigned long end,
 		struct vmem_altmap *altmap)
 {
+	mutex_lock(&vmem_mutex);
 	remove_pagetable(start, end, false);
+	mutex_unlock(&vmem_mutex);
 }
 
 void vmem_remove_mapping(unsigned long start, unsigned long size)
-- 
2.26.2