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Commit 082d5b6b authored by Gerald Schaefer's avatar Gerald Schaefer Committed by Linus Torvalds
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mm/hugetlb: check for reserved hugepages during memory offline 

In dissolve_free_huge_pages(), free hugepages will be dissolved without
making sure that there are enough of them left to satisfy hugepage
reservations.

Fix this by adding a return value to dissolve_free_huge_pages() and
checking h->free_huge_pages vs.  h->resv_huge_pages.  Note that this may
lead to the situation where dissolve_free_huge_page() returns an error
and all free hugepages that were dissolved before that error are lost,
while the memory block still cannot be set offline.

Fixes: c8721bbb ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
Link: http://lkml.kernel.org/r/20160926172811.94033-3-gerald.schaefer@de.ibm.com


Signed-off-by: default avatarGerald Schaefer <gerald.schaefer@de.ibm.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Acked-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Rui Teng <rui.teng@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2247bb33

include/linux/hugetlb.h

+3 −3
Original line number Diff line number Diff line
@@ -450,7 +450,7 @@ static inline pgoff_t basepage_index(struct page *page) 
	return __basepage_index(page);

}



extern void dissolve_free_huge_pages(unsigned long start_pfn,

extern int dissolve_free_huge_pages(unsigned long start_pfn,

				    unsigned long end_pfn);

static inline bool hugepage_migration_supported(struct hstate *h)

{
@@ -518,7 +518,7 @@ static inline pgoff_t basepage_index(struct page *page) 
{

	return page->index;

}

#define dissolve_free_huge_pages(s, e)	do {} while (0)

#define dissolve_free_huge_pages(s, e)	0

#define hugepage_migration_supported(h)	false



static inline spinlock_t *huge_pte_lockptr(struct hstate *h,

mm/hugetlb.c

+21 −5
Original line number Diff line number Diff line
@@ -1437,22 +1437,32 @@ static int free_pool_huge_page(struct hstate *h, nodemask_t *nodes_allowed, 


/*

 * Dissolve a given free hugepage into free buddy pages. This function does

 * nothing for in-use (including surplus) hugepages.

 * nothing for in-use (including surplus) hugepages. Returns -EBUSY if the

 * number of free hugepages would be reduced below the number of reserved

 * hugepages.

 */

static void dissolve_free_huge_page(struct page *page)

static int dissolve_free_huge_page(struct page *page)

{

	int rc = 0;



	spin_lock(&hugetlb_lock);

	if (PageHuge(page) && !page_count(page)) {

		struct page *head = compound_head(page);

		struct hstate *h = page_hstate(head);

		int nid = page_to_nid(head);

		if (h->free_huge_pages - h->resv_huge_pages == 0) {

			rc = -EBUSY;

			goto out;

		}

		list_del(&head->lru);

		h->free_huge_pages--;

		h->free_huge_pages_node[nid]--;

		h->max_huge_pages--;

		update_and_free_page(h, head);

	}

out:

	spin_unlock(&hugetlb_lock);

	return rc;

}



/*
@@ -1460,16 +1470,22 @@ static void dissolve_free_huge_page(struct page *page) 
 * make specified memory blocks removable from the system.

 * Note that this will dissolve a free gigantic hugepage completely, if any

 * part of it lies within the given range.

 * Also note that if dissolve_free_huge_page() returns with an error, all

 * free hugepages that were dissolved before that error are lost.

 */

void dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)

int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)

{

	unsigned long pfn;

	int rc = 0;



	if (!hugepages_supported())

		return;

		return rc;



	for (pfn = start_pfn; pfn < end_pfn; pfn += 1 << minimum_order)

		dissolve_free_huge_page(pfn_to_page(pfn));

		if (rc = dissolve_free_huge_page(pfn_to_page(pfn)))

			break;



	return rc;

}



/*

mm/memory_hotplug.c

+3 −1
Original line number Diff line number Diff line
@@ -1945,7 +1945,9 @@ static int __ref __offline_pages(unsigned long start_pfn, 
	 * dissolve free hugepages in the memory block before doing offlining

	 * actually in order to make hugetlbfs's object counting consistent.

	 */

	dissolve_free_huge_pages(start_pfn, end_pfn);

	ret = dissolve_free_huge_pages(start_pfn, end_pfn);

	if (ret)

		goto failed_removal;

	/* check again */

	offlined_pages = check_pages_isolated(start_pfn, end_pfn);

	if (offlined_pages < 0) {