smaps: extract pmd walker from smaps code

Extracts the pmd walker from smaps-specific code in fs/proc/task_mmu.c.

The new struct pmd_walker includes the struct vm_area_struct of the memory to
walk over.  Iteration begins at the vma->vm_start and completes at
vma->vm_end.  A pointer to another data structure may be stored in the private
field such as struct mem_size_stats, which acts as the smaps accumulator.  For
each pmd in the VMA, the action function is called with a pointer to its
struct vm_area_struct, a pointer to the pmd_t, its start and end addresses,
and the private field.

The interface for walking pmd's in a VMA for fs/proc/task_mmu.c is now:

	void for_each_pmd(struct vm_area_struct *vma,
			  void (*action)(struct vm_area_struct *vma,
					 pmd_t *pmd, unsigned long addr,
					 unsigned long end,
					 void *private),
			  void *private);

Since the pmd walker is now extracted from the smaps code, smaps_one_pmd() is
invoked for each pmd in the VMA.  Its behavior and efficiency is identical to
the existing implementation.

Cc: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 42 insertions, 27 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7445980c8022..9d22c1c1caa8 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -122,6 +122,13 @@ struct mem_size_stats
         unsigned long private_dirty;
 };
 
+struct pmd_walker {
+        struct vm_area_struct *vma;
+        void *private;
+        void (*action)(struct vm_area_struct *, pmd_t *, unsigned long,
+                       unsigned long, void *);
+};
+
 static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats *mss)
 {
         struct proc_maps_private *priv = m->private;
@@ -204,16 +211,17 @@ static int show_map(struct seq_file *m, void *v)
         return show_map_internal(m, v, NULL);
 }
 
-static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
-                                unsigned long addr, unsigned long end,
-                                struct mem_size_stats *mss)
+static void smaps_one_pmd(struct vm_area_struct *vma, pmd_t *pmd,
+                          unsigned long addr, unsigned long end,
+                          void *private)
 {
+        struct mem_size_stats *mss = private;
         pte_t *pte, ptent;
         spinlock_t *ptl;
         struct page *page;
 
         pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
-        do {
+        for (; addr != end; pte++, addr += PAGE_SIZE) {
                 ptent = *pte;
                 if (!pte_present(ptent))
                         continue;
@@ -235,57 +243,64 @@ static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                         else
                                 mss->private_clean += PAGE_SIZE;
                 }
-        } while (pte++, addr += PAGE_SIZE, addr != end);
+        }
         pte_unmap_unlock(pte - 1, ptl);
         cond_resched();
 }
 
-static inline void smaps_pmd_range(struct vm_area_struct *vma, pud_t *pud,
-                                unsigned long addr, unsigned long end,
-                                struct mem_size_stats *mss)
+static inline void for_each_pmd_in_pud(struct pmd_walker *walker, pud_t *pud,
+                                       unsigned long addr, unsigned long end)
 {
         pmd_t *pmd;
         unsigned long next;
 
-        pmd = pmd_offset(pud, addr);
-        do {
+        for (pmd = pmd_offset(pud, addr); addr != end;
+             pmd++, addr = next) {
                 next = pmd_addr_end(addr, end);
                 if (pmd_none_or_clear_bad(pmd))
                         continue;
-                smaps_pte_range(vma, pmd, addr, next, mss);
-        } while (pmd++, addr = next, addr != end);
+                walker->action(walker->vma, pmd, addr, next, walker->private);
+        }
 }
 
-static inline void smaps_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
-                                unsigned long addr, unsigned long end,
-                                struct mem_size_stats *mss)
+static inline void for_each_pud_in_pgd(struct pmd_walker *walker, pgd_t *pgd,
+                                       unsigned long addr, unsigned long end)
 {
         pud_t *pud;
         unsigned long next;
 
-        pud = pud_offset(pgd, addr);
-        do {
+        for (pud = pud_offset(pgd, addr); addr != end;
+             pud++, addr = next) {
                 next = pud_addr_end(addr, end);
                 if (pud_none_or_clear_bad(pud))
                         continue;
-                smaps_pmd_range(vma, pud, addr, next, mss);
-        } while (pud++, addr = next, addr != end);
+                for_each_pmd_in_pud(walker, pud, addr, next);
+        }
 }
 
-static inline void smaps_pgd_range(struct vm_area_struct *vma,
-                                unsigned long addr, unsigned long end,
-                                struct mem_size_stats *mss)
+static inline void for_each_pmd(struct vm_area_struct *vma,
+                                void (*action)(struct vm_area_struct *, pmd_t *,
+                                               unsigned long, unsigned long,
+                                               void *),
+                                void *private)
 {
+        unsigned long addr = vma->vm_start;
+        unsigned long end = vma->vm_end;
+        struct pmd_walker walker = {
+                .vma            = vma,
+                .private        = private,
+                .action         = action,
+        };
         pgd_t *pgd;
         unsigned long next;
 
-        pgd = pgd_offset(vma->vm_mm, addr);
-        do {
+        for (pgd = pgd_offset(vma->vm_mm, addr); addr != end;
+             pgd++, addr = next) {
                 next = pgd_addr_end(addr, end);
                 if (pgd_none_or_clear_bad(pgd))
                         continue;
-                smaps_pud_range(vma, pgd, addr, next, mss);
-        } while (pgd++, addr = next, addr != end);
+                for_each_pud_in_pgd(&walker, pgd, addr, next);
+        }
 }
 
 static int show_smap(struct seq_file *m, void *v)
@@ -295,7 +310,7 @@ static int show_smap(struct seq_file *m, void *v)
 
         memset(&mss, 0, sizeof mss);
         if (vma->vm_mm && !is_vm_hugetlb_page(vma))
-                smaps_pgd_range(vma, vma->vm_start, vma->vm_end, &mss);
+                for_each_pmd(vma, smaps_one_pmd, &mss);
         return show_map_internal(m, v, &mss);
 }