[PATCH] mm: unmap_vmas with inner ptlock

Remove the page_table_lock from around the calls to unmap_vmas, and replace
the pte_offset_map in zap_pte_range by pte_offset_map_lock: all callers are
now safe to descend without page_table_lock.

Don't attempt fancy locking for hugepages, just take page_table_lock in
unmap_hugepage_range.  Which makes zap_hugepage_range, and the hugetlb test in
zap_page_range, redundant: unmap_vmas calls unmap_hugepage_range anyway.  Nor
does unmap_vmas have much use for its mm arg now.

The tlb_start_vma and tlb_end_vma in unmap_page_range are now called without
page_table_lock: if they're implemented at all, they typically come down to
flush_cache_range (usually done outside page_table_lock) and flush_tlb_range
(which we already audited for the mprotect case).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 7 deletions

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 3a9b6d179cbd..a826a8add5e3 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -92,7 +92,7 @@ out:
 }
 
 /*
- * Called under down_write(mmap_sem), page_table_lock is not held
+ * Called under down_write(mmap_sem).
  */
 
 #ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
@@ -308,7 +308,6 @@ hugetlb_vmtruncate_list(struct prio_tree_root *root, unsigned long h_pgoff)
 
         vma_prio_tree_foreach(vma, &iter, root, h_pgoff, ULONG_MAX) {
                 unsigned long h_vm_pgoff;
-                unsigned long v_length;
                 unsigned long v_offset;
 
                 h_vm_pgoff = vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT);
@@ -319,11 +318,8 @@ hugetlb_vmtruncate_list(struct prio_tree_root *root, unsigned long h_pgoff)
                 if (h_vm_pgoff >= h_pgoff)
                         v_offset = 0;
 
-                v_length = vma->vm_end - vma->vm_start;
-
-                zap_hugepage_range(vma,
-                                vma->vm_start + v_offset,
-                                v_length - v_offset);
+                unmap_hugepage_range(vma,
+                                vma->vm_start + v_offset, vma->vm_end);
         }
 }