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powerpc: gup_hugepte() support THP based tail recounting
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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: Andrea Arcangeli <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: David Gibson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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aagit authored and torvalds committed Nov 2, 2011
1 parent 8596468 commit 3526741
Showing 1 changed file with 23 additions and 1 deletion.
24 changes: 23 additions & 1 deletion arch/powerpc/mm/hugetlbpage.c
Original file line number Diff line number Diff line change
Expand Up @@ -385,12 +385,23 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address,
return NULL;
}

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 noinline int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
unsigned long end, int write, struct page **pages, int *nr)
{
unsigned long mask;
unsigned long pte_end;
struct page *head, *page;
struct page *head, *page, *tail;
pte_t pte;
int refs;

Expand All @@ -413,6 +424,7 @@ static noinline int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long add
head = pte_page(pte);

page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
tail = page;
do {
VM_BUG_ON(compound_head(page) != head);
pages[*nr] = page;
Expand All @@ -431,6 +443,16 @@ static noinline int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long add
*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;
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