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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 121e6f3258 ("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@linux-foundation.org: whitespace fixes, per Christoph]

Link: https://lkml.kernel.org/r/20210614132357.10202-1-imbrenda@linux.ibm.com
Link: https://lkml.kernel.org/r/20210614132357.10202-2-imbrenda@linux.ibm.com
Fixes: 121e6f3258 ("mm/vmalloc: hugepage vmalloc mappings")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Claudio Imbrenda 2021-06-24 18:39:36 -07:00 committed by Linus Torvalds
parent 8fd0c1b064
commit 15a64f5a88
2 changed files with 18 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/vmalloc.h
View File

@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
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);

17
mm/vmalloc.c
View File

@ -2998,6 +2998,23 @@ 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