[ 54/58] sparc64: Fix get_user_pages_fast() wrt. THP.

Greg Kroah-Hartman
2013-02-25T22:20:38Z

From: "David S. Miller" <davem@davemloft.net>

[ Upstream commit 89a77915e0f56dc7b9f9082ba787895b6a83f809 ]

Mostly mirrors the s390 logic, as unlike x86 we don't need the
SetPageReferenced() bits.

On sparc64 we also lack a user/privileged bit in the huge PMDs.

In order to make this work for THP and non-THP builds, some header
file adjustments were necessary. Namely, provide the PMD_HUGE_* bit
defines and the pmd_large() inline unconditionally rather than
protected by TRANSPARENT_HUGEPAGE.

Reported-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/sparc/include/asm/pgtable_64.h | 14 +++-----
arch/sparc/mm/gup.c | 59 ++++++++++++++++++++++++++++++++++--
2 files changed, 63 insertions(+), 10 deletions(-)

--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -71,7 +71,6 @@
#define PMD_PADDR _AC(0xfffffffe,UL)
#define PMD_PADDR_SHIFT _AC(11,UL)

-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define PMD_ISHUGE _AC(0x00000001,UL)

/* This is the PMD layout when PMD_ISHUGE is set. With 4MB huge
@@ -86,7 +85,6 @@
#define PMD_HUGE_ACCESSED _AC(0x00000080,UL)
#define PMD_HUGE_EXEC _AC(0x00000040,UL)
#define PMD_HUGE_SPLITTING _AC(0x00000020,UL)
-#endif

/* PGDs point to PMD tables which are 8K aligned. */
#define PGD_PADDR _AC(0xfffffffc,UL)
@@ -622,6 +620,12 @@ static inline unsigned long pte_special(
return pte_val(pte) & _PAGE_SPECIAL;
}

+static inline int pmd_large(pmd_t pmd)
+{
+ return (pmd_val(pmd) & (PMD_ISHUGE | PMD_HUGE_PRESENT)) ==
+ (PMD_ISHUGE | PMD_HUGE_PRESENT);
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static inline int pmd_young(pmd_t pmd)
{
@@ -640,12 +644,6 @@ static inline unsigned long pmd_pfn(pmd_
return val >> (PAGE_SHIFT - PMD_PADDR_SHIFT);
}

-static inline int pmd_large(pmd_t pmd)
-{
- return (pmd_val(pmd) & (PMD_ISHUGE | PMD_HUGE_PRESENT)) ==
- (PMD_ISHUGE | PMD_HUGE_PRESENT);
-}
-
static inline int pmd_trans_splitting(pmd_t pmd)
{
return (pmd_val(pmd) & (PMD_ISHUGE|PMD_HUGE_SPLITTING)) ==
--- a/arch/sparc/mm/gup.c
+++ b/arch/sparc/mm/gup.c
@@ -66,6 +66,56 @@ static noinline int gup_pte_range(pmd_t
return 1;
}

+static int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr,
+ unsigned long end, int write, struct page **pages,
+ int *nr)
+{
+ struct page *head, *page, *tail;
+ u32 mask;
+ int refs;
+
+ mask = PMD_HUGE_PRESENT;
+ if (write)
+ mask |= PMD_HUGE_WRITE;
+ if ((pmd_val(pmd) & mask) != mask)
+ return 0;
+
+ 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;
+ (*nr)++;
+ page++;
+ refs++;
+ } while (addr += PAGE_SIZE, addr != end);
+
+ if (!page_cache_add_speculative(head, refs)) {
+ *nr -= refs;
+ return 0;
+ }
+
+ if (unlikely(pmd_val(pmd) != pmd_val(*pmdp))) {
+ *nr -= refs;
+ while (refs--)
+ put_page(head);
+ return 0;
+ }
+
+ /* Any tail page need their mapcount reference taken before we
+ * return.
+ */
+ while (refs--) {
+ if (PageTail(tail))
+ get_huge_page_tail(tail);
+ tail++;
+ }
+
+ return 1;
+}
+
static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
int write, struct page **pages, int *nr)
{
@@ -77,9 +127,14 @@ static int gup_pmd_range(pud_t pud, unsi
pmd_t pmd = *pmdp;

next = pmd_addr_end(addr, end);
- if (pmd_none(pmd))
+ if (pmd_none(pmd) || pmd_trans_splitting(pmd))
return 0;
- if (!gup_pte_range(pmd, addr, next, write, pages, nr))
+ if (unlikely(pmd_large(pmd))) {
+ if (!gup_huge_pmd(pmdp, pmd, addr, next,
+ write, pages, nr))
+ return 0;
+ } else if (!gup_pte_range(pmd, addr, next, write,
+ pages, nr))
return 0;
} while (pmdp++, addr = next, addr != end);