mm: FOLL flags for GUP flags

__get_user_pages() has been taking its own GUP flags, then processing
them into FOLL flags for follow_page().  Though oddly named, the FOLL
flags are more widely used, so pass them to __get_user_pages() now.
Sorry, VM flags, VM_FAULT flags and FAULT_FLAGs are still distinct.

(The patch to __get_user_pages() looks peculiar, with both gup_flags
and foll_flags: the gup_flags remain constant; but as before there's
an exceptional case, out of scope of the patch, in which foll_flags
per page have FOLL_WRITE masked off.)

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Rik van Riel <riel@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 25 deletions

diff --git a/mm/memory.c b/mm/memory.c
index c8b5b9435a92..5c694f2b9c12 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1209,27 +1209,29 @@ no_page_table:
 }
 
 int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
-                     unsigned long start, int nr_pages, int flags,
+                     unsigned long start, int nr_pages, unsigned int gup_flags,
                      struct page **pages, struct vm_area_struct **vmas)
 {
         int i;
-        unsigned int vm_flags = 0;
-        int write = !!(flags & GUP_FLAGS_WRITE);
-        int force = !!(flags & GUP_FLAGS_FORCE);
+        unsigned long vm_flags;
 
         if (nr_pages <= 0)
                 return 0;
+
+        VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
+
         /* 
          * Require read or write permissions.
-         * If 'force' is set, we only require the "MAY" flags.
+         * If FOLL_FORCE is set, we only require the "MAY" flags.
          */
-        vm_flags  = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
-        vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
+        vm_flags  = (gup_flags & FOLL_WRITE) ?
+                        (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
+        vm_flags &= (gup_flags & FOLL_FORCE) ?
+                        (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
         i = 0;
 
         do {
                 struct vm_area_struct *vma;
-                unsigned int foll_flags;
 
                 vma = find_extend_vma(mm, start);
                 if (!vma && in_gate_area(tsk, start)) {
@@ -1241,7 +1243,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         pte_t *pte;
 
                         /* user gate pages are read-only */
-                        if (write)
+                        if (gup_flags & FOLL_WRITE)
                                 return i ? : -EFAULT;
                         if (pg > TASK_SIZE)
                                 pgd = pgd_offset_k(pg);
@@ -1278,22 +1280,15 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                     !(vm_flags & vma->vm_flags))
                         return i ? : -EFAULT;
 
-                foll_flags = FOLL_TOUCH;
-                if (pages)
-                        foll_flags |= FOLL_GET;
-                if (flags & GUP_FLAGS_DUMP)
-                        foll_flags |= FOLL_DUMP;
-                if (write)
-                        foll_flags |= FOLL_WRITE;
-
                 if (is_vm_hugetlb_page(vma)) {
                         i = follow_hugetlb_page(mm, vma, pages, vmas,
-                                        &start, &nr_pages, i, foll_flags);
+                                        &start, &nr_pages, i, gup_flags);
                         continue;
                 }
 
                 do {
                         struct page *page;
+                        unsigned int foll_flags = gup_flags;
 
                         /*
                          * If we have a pending SIGKILL, don't keep faulting
@@ -1302,9 +1297,6 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         if (unlikely(fatal_signal_pending(current)))
                                 return i ? i : -ERESTARTSYS;
 
-                        if (write)
-                                foll_flags |= FOLL_WRITE;
-
                         cond_resched();
                         while (!(page = follow_page(vma, start, foll_flags))) {
                                 int ret;
@@ -1415,12 +1407,14 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                 unsigned long start, int nr_pages, int write, int force,
                 struct page **pages, struct vm_area_struct **vmas)
 {
-        int flags = 0;
+        int flags = FOLL_TOUCH;
 
+        if (pages)
+                flags |= FOLL_GET;
         if (write)
-                flags |= GUP_FLAGS_WRITE;
+                flags |= FOLL_WRITE;
         if (force)
-                flags |= GUP_FLAGS_FORCE;
+                flags |= FOLL_FORCE;
 
         return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
 }
@@ -1447,7 +1441,7 @@ struct page *get_dump_page(unsigned long addr)
         struct page *page;
 
         if (__get_user_pages(current, current->mm, addr, 1,
-                        GUP_FLAGS_FORCE | GUP_FLAGS_DUMP, &page, &vma) < 1)
+                        FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1)
                 return NULL;
         if (page == ZERO_PAGE(0)) {
                 page_cache_release(page);