mincore: cleanups

This fixes some minor issues that bugged me while going over the code:

o adjust argument order of do_mincore() to match the syscall
o simplify range length calculation
o drop superfluous shift in huge tlb calculation, address is page aligned
o drop dead nr_huge calculation
o check pte_none() before pte_present()
o comment and whitespace fixes

No semantic changes intended.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 49 deletions

diff --git a/mm/mincore.c b/mm/mincore.c
index f77433c20279..1f6574c5167b 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -54,7 +54,7 @@ static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
  * all the arguments, we hold the mmap semaphore: we should
  * just return the amount of info we're asked for.
  */
-static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pages)
+static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
 {
         pgd_t *pgd;
         pud_t *pud;
@@ -64,35 +64,29 @@ static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pag
         unsigned long nr;
         int i;
         pgoff_t pgoff;
-        struct vm_area_struct *vma = find_vma(current->mm, addr);
+        struct vm_area_struct *vma;
 
-        /*
-         * find_vma() didn't find anything above us, or we're
-         * in an unmapped hole in the address space: ENOMEM.
-         */
+        vma = find_vma(current->mm, addr);
         if (!vma || addr < vma->vm_start)
                 return -ENOMEM;
 
+        nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
+
 #ifdef CONFIG_HUGETLB_PAGE
         if (is_vm_hugetlb_page(vma)) {
                 struct hstate *h;
-                unsigned long nr_huge;
-                unsigned char present;
 
                 i = 0;
-                nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
                 h = hstate_vma(vma);
-                nr_huge = ((addr + pages * PAGE_SIZE - 1) >> huge_page_shift(h))
-                          - (addr >> huge_page_shift(h)) + 1;
-                nr_huge = min(nr_huge,
-                              (vma->vm_end - addr) >> huge_page_shift(h));
                 while (1) {
-                        /* hugepage always in RAM for now,
-                         * but generally it needs to be check */
+                        unsigned char present;
+                        /*
+                         * Huge pages are always in RAM for now, but
+                         * theoretically it needs to be checked.
+                         */
                         ptep = huge_pte_offset(current->mm,
                                                addr & huge_page_mask(h));
-                        present = !!(ptep &&
-                                     !huge_pte_none(huge_ptep_get(ptep)));
+                        present = ptep && !huge_pte_none(huge_ptep_get(ptep));
                         while (1) {
                                 vec[i++] = present;
                                 addr += PAGE_SIZE;
@@ -100,8 +94,7 @@ static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pag
                                 if (i == nr)
                                         return nr;
                                 /* check hugepage border */
-                                if (!((addr & ~huge_page_mask(h))
-                                      >> PAGE_SHIFT))
+                                if (!(addr & ~huge_page_mask(h)))
                                         break;
                         }
                 }
@@ -113,17 +106,7 @@ static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pag
          * Calculate how many pages there are left in the last level of the
          * PTE array for our address.
          */
-        nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1));
-
-        /*
-         * Don't overrun this vma
-         */
-        nr = min(nr, (vma->vm_end - addr) >> PAGE_SHIFT);
-
-        /*
-         * Don't return more than the caller asked for
-         */
-        nr = min(nr, pages);
+        nr = min(nr, PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1)));
 
         pgd = pgd_offset(vma->vm_mm, addr);
         if (pgd_none_or_clear_bad(pgd))
@@ -137,43 +120,38 @@ static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pag
 
         ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
         for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) {
-                unsigned char present;
                 pte_t pte = *ptep;
 
-                if (pte_present(pte)) {
-                        present = 1;
-
-                } else if (pte_none(pte)) {
+                if (pte_none(pte)) {
                         if (vma->vm_file) {
                                 pgoff = linear_page_index(vma, addr);
-                                present = mincore_page(vma->vm_file->f_mapping,
-                                                        pgoff);
+                                vec[i] = mincore_page(vma->vm_file->f_mapping,
+                                                pgoff);
                         } else
-                                present = 0;
-
-                } else if (pte_file(pte)) {
+                                vec[i] = 0;
+                } else if (pte_present(pte))
+                        vec[i] = 1;
+                else if (pte_file(pte)) {
                         pgoff = pte_to_pgoff(pte);
-                        present = mincore_page(vma->vm_file->f_mapping, pgoff);
-
+                        vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
                 } else { /* pte is a swap entry */
                         swp_entry_t entry = pte_to_swp_entry(pte);
+
                         if (is_migration_entry(entry)) {
                                 /* migration entries are always uptodate */
-                                present = 1;
+                                vec[i] = 1;
                         } else {
 #ifdef CONFIG_SWAP
                                 pgoff = entry.val;
-                                present = mincore_page(&swapper_space, pgoff);
+                                vec[i] = mincore_page(&swapper_space, pgoff);
 #else
                                 WARN_ON(1);
-                                present = 1;
+                                vec[i] = 1;
 #endif
                         }
                 }
-
-                vec[i] = present;
         }
-        pte_unmap_unlock(ptep-1, ptl);
+        pte_unmap_unlock(ptep - 1, ptl);
 
         return nr;
 
@@ -247,7 +225,7 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
                  * the temporary buffer size.
                  */
                 down_read(&current->mm->mmap_sem);
-                retval = do_mincore(start, tmp, min(pages, PAGE_SIZE));
+                retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
                 up_read(&current->mm->mmap_sem);
 
                 if (retval <= 0)