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Revision e700898fa075c69b3ae02b702ab57fb75e1a82ec authored by Mike Kravetz on 12 December 2022, 23:50:41 UTC, committed by Andrew Morton on 21 December 2022, 22:31:52 UTC 
hugetlb: really allocate vma lock for all sharable vmas
 
Commit bbff39cc6cbc ("hugetlb: allocate vma lock for all sharable vmas")
removed the pmd sharable checks in the vma lock helper routines.  However,
it left the functional version of helper routines behind #ifdef
CONFIG_ARCH_WANT_HUGE_PMD_SHARE.  Therefore, the vma lock is not being
used for sharable vmas on architectures that do not support pmd sharing. 
On these architectures, a potential fault/truncation race is exposed that
could leave pages in a hugetlb file past i_size until the file is removed.

Move the functional vma lock helpers outside the ifdef, and remove the
non-functional stubs.  Since the vma lock is not just for pmd sharing,
rename the routine __vma_shareable_flags_pmd.

Link: https://lkml.kernel.org/r/20221212235042.178355-1-mike.kravetz@oracle.com
Fixes: bbff39cc6cbc ("hugetlb: allocate vma lock for all sharable vmas")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
1 parent 7ba594d
Raw File
hugetlb_vmemmap.h 
// SPDX-License-Identifier: GPL-2.0
/*
 * HugeTLB Vmemmap Optimization (HVO)
 *
 * Copyright (c) 2020, ByteDance. All rights reserved.
 *
 *     Author: Muchun Song <songmuchun@bytedance.com>
 */
#ifndef _LINUX_HUGETLB_VMEMMAP_H
#define _LINUX_HUGETLB_VMEMMAP_H
#include <linux/hugetlb.h>

#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head);
void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head);

/*
 * Reserve one vmemmap page, all vmemmap addresses are mapped to it. See
 * Documentation/vm/vmemmap_dedup.rst.
 */
#define HUGETLB_VMEMMAP_RESERVE_SIZE	PAGE_SIZE

static inline unsigned int hugetlb_vmemmap_size(const struct hstate *h)
{
	return pages_per_huge_page(h) * sizeof(struct page);
}

/*
 * Return how many vmemmap size associated with a HugeTLB page that can be
 * optimized and can be freed to the buddy allocator.
 */
static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
{
	int size = hugetlb_vmemmap_size(h) - HUGETLB_VMEMMAP_RESERVE_SIZE;

	if (!is_power_of_2(sizeof(struct page)))
		return 0;
	return size > 0 ? size : 0;
}
#else
static inline int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
{
	return 0;
}

static inline void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
{
}

static inline unsigned int hugetlb_vmemmap_optimizable_size(const struct hstate *h)
{
	return 0;
}
#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */

static inline bool hugetlb_vmemmap_optimizable(const struct hstate *h)
{
	return hugetlb_vmemmap_optimizable_size(h) != 0;
}
#endif /* _LINUX_HUGETLB_VMEMMAP_H */
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