[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, 9 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ea0826ff2663..f29b7dc02c39 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -314,6 +314,8 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 	BUG_ON(start & ~HPAGE_MASK);
 	BUG_ON(end & ~HPAGE_MASK);
 
+	spin_lock(&mm->page_table_lock);
+
 	/* Update high watermark before we lower rss */
 	update_hiwater_rss(mm);
 
@@ -333,17 +335,9 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
 		put_page(page);
 		add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
 	}
-	flush_tlb_range(vma, start, end);
-}
 
-void zap_hugepage_range(struct vm_area_struct *vma,
-			unsigned long start, unsigned long length)
-{
-	struct mm_struct *mm = vma->vm_mm;
-
-	spin_lock(&mm->page_table_lock);
-	unmap_hugepage_range(vma, start, start + length);
 	spin_unlock(&mm->page_table_lock);
+	flush_tlb_range(vma, start, end);
 }
 
 int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)