mm: cleanup __get_user_pages()

Get rid of two nested loops over nr_pages, extract vma flags checking to
separate function and other random cleanups.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 28e3700..cc5a9e7 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -315,6 +315,44 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
        return 0;
 }
 
+static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
+{
+       vm_flags_t vm_flags = vma->vm_flags;
+
+       if (vm_flags & (VM_IO | VM_PFNMAP))
+               return -EFAULT;
+
+       if (gup_flags & FOLL_WRITE) {
+               if (!(vm_flags & VM_WRITE)) {
+                       if (!(gup_flags & FOLL_FORCE))
+                               return -EFAULT;
+                       /*
+                        * We used to let the write,force case do COW in a
+                        * VM_MAYWRITE VM_SHARED !VM_WRITE vma, so ptrace could
+                        * set a breakpoint in a read-only mapping of an
+                        * executable, without corrupting the file (yet only
+                        * when that file had been opened for writing!).
+                        * Anon pages in shared mappings are surprising: now
+                        * just reject it.
+                        */
+                       if (!is_cow_mapping(vm_flags)) {
+                               WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
+                               return -EFAULT;
+                       }
+               }
+       } else if (!(vm_flags & VM_READ)) {
+               if (!(gup_flags & FOLL_FORCE))
+                       return -EFAULT;
+               /*
+                * Is there actually any vma we can reach here which does not
+                * have VM_MAYREAD set?
+                */
+               if (!(vm_flags & VM_MAYREAD))
+                       return -EFAULT;
+       }
+       return 0;
+}
+
 /**
  * __get_user_pages() - pin user pages in memory
  * @tsk:       task_struct of target task
@@ -369,9 +407,9 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                unsigned int gup_flags, struct page **pages,
                struct vm_area_struct **vmas, int *nonblocking)
 {
-       long i;
-       unsigned long vm_flags;
+       long i = 0;
        unsigned int page_mask;
+       struct vm_area_struct *vma = NULL;
 
        if (!nr_pages)
                return 0;
@@ -386,124 +424,82 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
        if (!(gup_flags & FOLL_FORCE))
                gup_flags |= FOLL_NUMA;
 
-       i = 0;
-
        do {
-               struct vm_area_struct *vma;
-
-               vma = find_extend_vma(mm, start);
-               if (!vma && in_gate_area(mm, start)) {
-                       int ret;
-                       ret = get_gate_page(mm, start & PAGE_MASK, gup_flags,
-                                       &vma, pages ? &pages[i] : NULL);
-                       if (ret)
-                               goto efault;
-                       page_mask = 0;
-                       goto next_page;
-               }
+               struct page *page;
+               unsigned int foll_flags = gup_flags;
+               unsigned int page_increm;
+
+               /* first iteration or cross vma bound */
+               if (!vma || start >= vma->vm_end) {
+                       vma = find_extend_vma(mm, start);
+                       if (!vma && in_gate_area(mm, start)) {
+                               int ret;
+                               ret = get_gate_page(mm, start & PAGE_MASK,
+                                               gup_flags, &vma,
+                                               pages ? &pages[i] : NULL);
+                               if (ret)
+                                       return i ? : ret;
+                               page_mask = 0;
+                               goto next_page;
+                       }
 
-               if (!vma)
-                       goto efault;
-               vm_flags = vma->vm_flags;
-               if (vm_flags & (VM_IO | VM_PFNMAP))
-                       goto efault;
-
-               if (gup_flags & FOLL_WRITE) {
-                       if (!(vm_flags & VM_WRITE)) {
-                               if (!(gup_flags & FOLL_FORCE))
-                                       goto efault;
-                               /*
-                                * We used to let the write,force case do COW
-                                * in a VM_MAYWRITE VM_SHARED !VM_WRITE vma, so
-                                * ptrace could set a breakpoint in a read-only
-                                * mapping of an executable, without corrupting
-                                * the file (yet only when that file had been
-                                * opened for writing!).  Anon pages in shared
-                                * mappings are surprising: now just reject it.
-                                */
-                               if (!is_cow_mapping(vm_flags)) {
-                                       WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
-                                       goto efault;
-                               }
+                       if (!vma || check_vma_flags(vma, gup_flags))
+                               return i ? : -EFAULT;
+                       if (is_vm_hugetlb_page(vma)) {
+                               i = follow_hugetlb_page(mm, vma, pages, vmas,
+                                               &start, &nr_pages, i,
+                                               gup_flags);
+                               continue;
                        }
-               } else {
-                       if (!(vm_flags & VM_READ)) {
-                               if (!(gup_flags & FOLL_FORCE))
-                                       goto efault;
-                               /*
-                                * Is there actually any vma we can reach here
-                                * which does not have VM_MAYREAD set?
-                                */
-                               if (!(vm_flags & VM_MAYREAD))
-                                       goto efault;
+               }
+retry:
+               /*
+                * If we have a pending SIGKILL, don't keep faulting pages and
+                * potentially allocating memory.
+                */
+               if (unlikely(fatal_signal_pending(current)))
+                       return i ? i : -ERESTARTSYS;
+               cond_resched();
+               page = follow_page_mask(vma, start, foll_flags, &page_mask);
+               if (!page) {
+                       int ret;
+                       ret = faultin_page(tsk, vma, start, &foll_flags,
+                                       nonblocking);
+                       switch (ret) {
+                       case 0:
+                               goto retry;
+                       case -EFAULT:
+                       case -ENOMEM:
+                       case -EHWPOISON:
+                               return i ? i : ret;
+                       case -EBUSY:
+                               return i;
+                       case -ENOENT:
+                               goto next_page;
                        }
+                       BUG();
                }
-
-               if (is_vm_hugetlb_page(vma)) {
-                       i = follow_hugetlb_page(mm, vma, pages, vmas,
-                                       &start, &nr_pages, i, gup_flags);
-                       continue;
+               if (IS_ERR(page))
+                       return i ? i : PTR_ERR(page);
+               if (pages) {
+                       pages[i] = page;
+                       flush_anon_page(vma, page, start);
+                       flush_dcache_page(page);
+                       page_mask = 0;
                }
-
-               do {
-                       struct page *page;
-                       unsigned int foll_flags = gup_flags;
-                       unsigned int page_increm;
-
-                       /*
-                        * If we have a pending SIGKILL, don't keep faulting
-                        * pages and potentially allocating memory.
-                        */
-                       if (unlikely(fatal_signal_pending(current)))
-                               return i ? i : -ERESTARTSYS;
-
-                       cond_resched();
-                       while (!(page = follow_page_mask(vma, start,
-                                               foll_flags, &page_mask))) {
-                               int ret;
-                               ret = faultin_page(tsk, vma, start, &foll_flags,
-                                               nonblocking);
-                               switch (ret) {
-                               case 0:
-                                       break;
-                               case -EFAULT:
-                               case -ENOMEM:
-                               case -EHWPOISON:
-                                       return i ? i : ret;
-                               case -EBUSY:
-                                       return i;
-                               case -ENOENT:
-                                       goto next_page;
-                               default:
-                                       BUG();
-                               }
-                               cond_resched();
-                       }
-                       if (IS_ERR(page))
-                               return i ? i : PTR_ERR(page);
-                       if (pages) {
-                               pages[i] = page;
-
-                               flush_anon_page(vma, page, start);
-                               flush_dcache_page(page);
-                               page_mask = 0;
-                       }
 next_page:
-                       if (vmas) {
-                               vmas[i] = vma;
-                               page_mask = 0;
-                       }
-                       page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
-                       if (page_increm > nr_pages)
-                               page_increm = nr_pages;
-                       i += page_increm;
-                       start += page_increm * PAGE_SIZE;
-                       nr_pages -= page_increm;
-               } while (nr_pages && start < vma->vm_end);
+               if (vmas) {
+                       vmas[i] = vma;
+                       page_mask = 0;
+               }
+               page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
+               if (page_increm > nr_pages)
+                       page_increm = nr_pages;
+               i += page_increm;
+               start += page_increm * PAGE_SIZE;
+               nr_pages -= page_increm;
        } while (nr_pages);
        return i;
-efault:
-       return i ? : -EFAULT;
 }
 EXPORT_SYMBOL(__get_user_pages);