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Commit 220a2eb2 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds
Browse files

s390: gup_huge_pmd() support THP tail recounting 



Up to this point the code assumed old refcounting for hugepages (pre-thp).
This updates the code directly to the thp mapcount tail page refcounting.

Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cf592bf7

arch/s390/mm/gup.c

+23 −1
Original line number Diff line number Diff line
@@ -48,11 +48,22 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, 
	return 1;

}



static inline void get_huge_page_tail(struct page *page)

{

	/*

	 * __split_huge_page_refcount() cannot run

	 * from under us.

	 */

	VM_BUG_ON(page_mapcount(page) < 0);

	VM_BUG_ON(atomic_read(&page->_count) != 0);

	atomic_inc(&page->_mapcount);

}



static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,

		unsigned long end, int write, struct page **pages, int *nr)

{

	unsigned long mask, result;

	struct page *head, *page;

	struct page *head, *page, *tail;

	int refs;



	result = write ? 0 : _SEGMENT_ENTRY_RO;
@@ -64,6 +75,7 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, 
	refs = 0;

	head = pmd_page(pmd);

	page = head + ((addr & ~PMD_MASK) >> PAGE_SHIFT);

	tail = page;

	do {

		VM_BUG_ON(compound_head(page) != head);

		pages[*nr] = page;
@@ -81,6 +93,16 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, 
		*nr -= refs;

		while (refs--)

			put_page(head);

	} else {

		/*

		 * Any tail page need their mapcount reference taken

		 * before we return.

		 */

		while (refs--) {

			if (PageTail(tail))

				get_huge_page_tail(tail);

			tail++;

		}

	}



	return 1;