From: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Subject: mm/vmalloc: add vmalloc_no_huge
Patch series "mm: add vmalloc_no_huge and use it", v4.
Add vmalloc_no_huge() and export it, so modules can allocate memory with
small pages.
Use the newly added vmalloc_no_huge() in KVM on s390 to get around a
hardware limitation.
This patch (of 2):
Commit 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") added
support for hugepage vmalloc mappings, it also added the flag
VM_NO_HUGE_VMAP for __vmalloc_node_range to request the allocation to be
performed with 0-order non-huge pages. This flag is not accessible when
calling vmalloc, the only option is to call directly __vmalloc_node_range,
which is not exported.
This means that a module can't vmalloc memory with small pages.
Case in point: KVM on s390x needs to vmalloc a large area, and it needs to
be mapped with non-huge pages, because of a hardware limitation.
This patch adds the function vmalloc_no_huge, which works like vmalloc,
but it is guaranteed to always back the mapping using small pages. This
new function is exported, therefore it is usable by modules.
[akpm@xxxxxxxxxxxxxxxxxxxx: whitespace fixes, per Christoph]
Link: https://lkml.kernel.org/r/20210614132357.10202-1-imbrenda@xxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20210614132357.10202-2-imbrenda@xxxxxxxxxxxxx
Fixes: 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings")
Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Acked-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Cornelia Huck <cohuck@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/vmalloc.h | 1 +
mm/vmalloc.c | 17 +++++++++++++++++
2 files changed, 18 insertions(+)
--- a/include/linux/vmalloc.h~mm-vmalloc-add-vmalloc_no_huge
+++ a/include/linux/vmalloc.h
@@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsign
const void *caller);
void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
int node, const void *caller);
+void *vmalloc_no_huge(unsigned long size);
extern void vfree(const void *addr);
extern void vfree_atomic(const void *addr);
--- a/mm/vmalloc.c~mm-vmalloc-add-vmalloc_no_huge
+++ a/mm/vmalloc.c
@@ -2999,6 +2999,23 @@ void *vmalloc(unsigned long size)
EXPORT_SYMBOL(vmalloc);
/**
+ * vmalloc_no_huge - allocate virtually contiguous memory using small pages
+ * @size: allocation size
+ *
+ * Allocate enough non-huge pages to cover @size from the page level
+ * allocator and map them into contiguous kernel virtual space.
+ *
+ * Return: pointer to the allocated memory or %NULL on error
+ */
+void *vmalloc_no_huge(unsigned long size)
+{
+ return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
+ GFP_KERNEL, PAGE_KERNEL, VM_NO_HUGE_VMAP,
+ NUMA_NO_NODE, __builtin_return_address(0));
+}
+EXPORT_SYMBOL(vmalloc_no_huge);
+
+/**
* vzalloc - allocate virtually contiguous memory with zero fill
* @size: allocation size
*
_
