mm: follow_hugetlb_page flags

follow_hugetlb_page() shouldn't be guessing about the coredump case
either: pass the foll_flags down to it, instead of just the write bit.

Remove that obscure huge_zeropage_ok() test.  The decision is easy,
though unlike the non-huge case - here vm_ops->fault is always set.
But we know that a fault would serve up zeroes, unless there's
already a hugetlbfs pagecache page to back the range.

(Alternatively, since hugetlb pages aren't swapped out under pressure,
you could save more dump space by arguing that a page not yet faulted
into this process cannot be relevant to the dump; but that would be
more surprising.)

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: 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, 8 insertions, 6 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 532a55bce6a4..6359a4f80c4a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1260,17 +1260,19 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                     !(vm_flags & vma->vm_flags))
                         return i ? : -EFAULT;
 
-                if (is_vm_hugetlb_page(vma)) {
-                        i = follow_hugetlb_page(mm, vma, pages, vmas,
-                                                &start, &nr_pages, i, write);
-                        continue;
-                }
-
                 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);
+                        continue;
+                }
 
                 do {
                         struct page *page;