mincore: cleanups
Johannes Weiner [Mon, 24 May 2010 21:32:09 +0000 (14:32 -0700)]
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>

mm/mincore.c

index f77433c..1f6574c 100644 (file)
@@ -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)