pagemap: introduce data structure for pagemap entry

Currently a local variable of pagemap entry in pagemap_pte_range() is
named pfn and typed with u64, but it's not correct (pfn should be unsigned
long.)

This patch introduces special type for pagemap entries and replaces code
with it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 38 insertions, 31 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 328843de6e9f..c7e3a163295c 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -594,9 +594,13 @@ const struct file_operations proc_clear_refs_operations = {
         .llseek         = noop_llseek,
 };
 
+typedef struct {
+        u64 pme;
+} pagemap_entry_t;
+
 struct pagemapread {
         int pos, len;
-        u64 *buffer;
+        pagemap_entry_t *buffer;
 };
 
 #define PAGEMAP_WALK_SIZE       (PMD_SIZE)
@@ -619,10 +623,15 @@ struct pagemapread {
 #define PM_NOT_PRESENT      PM_PSHIFT(PAGE_SHIFT)
 #define PM_END_OF_BUFFER    1
 
-static int add_to_pagemap(unsigned long addr, u64 pfn,
+static inline pagemap_entry_t make_pme(u64 val)
+{
+        return (pagemap_entry_t) { .pme = val };
+}
+
+static int add_to_pagemap(unsigned long addr, pagemap_entry_t *pme,
                           struct pagemapread *pm)
 {
-        pm->buffer[pm->pos++] = pfn;
+        pm->buffer[pm->pos++] = *pme;
         if (pm->pos >= pm->len)
                 return PM_END_OF_BUFFER;
         return 0;
@@ -634,8 +643,10 @@ static int pagemap_pte_hole(unsigned long start, unsigned long end,
         struct pagemapread *pm = walk->private;
         unsigned long addr;
         int err = 0;
+        pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);
+
         for (addr = start; addr < end; addr += PAGE_SIZE) {
-                err = add_to_pagemap(addr, PM_NOT_PRESENT, pm);
+                err = add_to_pagemap(addr, &pme, pm);
                 if (err)
                         break;
         }
@@ -648,36 +659,33 @@ static u64 swap_pte_to_pagemap_entry(pte_t pte)
         return swp_type(e) | (swp_offset(e) << MAX_SWAPFILES_SHIFT);
 }
 
-static u64 pte_to_pagemap_entry(pte_t pte)
+static void pte_to_pagemap_entry(pagemap_entry_t *pme, pte_t pte)
 {
-        u64 pme = 0;
         if (is_swap_pte(pte))
-                pme = PM_PFRAME(swap_pte_to_pagemap_entry(pte))
-                        | PM_PSHIFT(PAGE_SHIFT) | PM_SWAP;
+                *pme = make_pme(PM_PFRAME(swap_pte_to_pagemap_entry(pte))
+                                | PM_PSHIFT(PAGE_SHIFT) | PM_SWAP);
         else if (pte_present(pte))
-                pme = PM_PFRAME(pte_pfn(pte))
-                        | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
-        return pme;
+                *pme = make_pme(PM_PFRAME(pte_pfn(pte))
+                                | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static u64 thp_pmd_to_pagemap_entry(pmd_t pmd, int offset)
+static void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
+                                        pmd_t pmd, int offset)
 {
-        u64 pme = 0;
         /*
          * Currently pmd for thp is always present because thp can not be
          * swapped-out, migrated, or HWPOISONed (split in such cases instead.)
          * This if-check is just to prepare for future implementation.
          */
         if (pmd_present(pmd))
-                pme = PM_PFRAME(pmd_pfn(pmd) + offset)
-                        | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
-        return pme;
+                *pme = make_pme(PM_PFRAME(pmd_pfn(pmd) + offset)
+                                | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
 }
 #else
-static inline u64 thp_pmd_to_pagemap_entry(pmd_t pmd, int offset)
+static inline void thp_pmd_to_pagemap_entry(pagemap_entry_t *pme,
+                                                pmd_t pmd, int offset)
 {
-        return 0;
 }
 #endif
 
@@ -688,7 +696,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
         struct pagemapread *pm = walk->private;
         pte_t *pte;
         int err = 0;
-        u64 pfn = PM_NOT_PRESENT;
+        pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);
 
         if (pmd_trans_unstable(pmd))
                 return 0;
@@ -702,8 +710,8 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 
                         offset = (addr & ~PAGEMAP_WALK_MASK) >>
                                         PAGE_SHIFT;
-                        pfn = thp_pmd_to_pagemap_entry(*pmd, offset);
-                        err = add_to_pagemap(addr, pfn, pm);
+                        thp_pmd_to_pagemap_entry(&pme, *pmd, offset);
+                        err = add_to_pagemap(addr, &pme, pm);
                         if (err)
                                 break;
                 }
@@ -723,11 +731,11 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
                 if (vma && (vma->vm_start <= addr) &&
                     !is_vm_hugetlb_page(vma)) {
                         pte = pte_offset_map(pmd, addr);
-                        pfn = pte_to_pagemap_entry(*pte);
+                        pte_to_pagemap_entry(&pme, *pte);
                         /* unmap before userspace copy */
                         pte_unmap(pte);
                 }
-                err = add_to_pagemap(addr, pfn, pm);
+                err = add_to_pagemap(addr, &pme, pm);
                 if (err)
                         return err;
         }
@@ -738,13 +746,12 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 }
 
 #ifdef CONFIG_HUGETLB_PAGE
-static u64 huge_pte_to_pagemap_entry(pte_t pte, int offset)
+static void huge_pte_to_pagemap_entry(pagemap_entry_t *pme,
+                                        pte_t pte, int offset)
 {
-        u64 pme = 0;
         if (pte_present(pte))
-                pme = PM_PFRAME(pte_pfn(pte) + offset)
-                        | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT;
-        return pme;
+                *pme = make_pme(PM_PFRAME(pte_pfn(pte) + offset)
+                                | PM_PSHIFT(PAGE_SHIFT) | PM_PRESENT);
 }
 
 /* This function walks within one hugetlb entry in the single call */
@@ -754,12 +761,12 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask,
 {
         struct pagemapread *pm = walk->private;
         int err = 0;
-        u64 pfn;
+        pagemap_entry_t pme = make_pme(PM_NOT_PRESENT);
 
         for (; addr != end; addr += PAGE_SIZE) {
                 int offset = (addr & ~hmask) >> PAGE_SHIFT;
-                pfn = huge_pte_to_pagemap_entry(*pte, offset);
-                err = add_to_pagemap(addr, pfn, pm);
+                huge_pte_to_pagemap_entry(&pme, *pte, offset);
+                err = add_to_pagemap(addr, &pme, pm);
                 if (err)
                         return err;
         }