ksm: add cond_resched() to the rmap_walks

While at it add it to the file and anon walks too.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Petr Holasek <pholasek@redhat.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/ksm.c

@@ -1914,9 +1914,11 @@ int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
 		struct anon_vma_chain *vmac;
 		struct vm_area_struct *vma;
 
+		cond_resched();
 		anon_vma_lock_read(anon_vma);
 		anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root,
 					       0, ULONG_MAX) {
+			cond_resched();
 			vma = vmac->vma;
 			if (rmap_item->address < vma->vm_start ||
 			    rmap_item->address >= vma->vm_end)

mm/rmap.c

@@ -1609,6 +1609,8 @@ static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
 		struct vm_area_struct *vma = avc->vma;
 		unsigned long address = vma_address(page, vma);
 
+		cond_resched();
+
 		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
 			continue;
 
@@ -1658,6 +1660,8 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
 	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
 		unsigned long address = vma_address(page, vma);
 
+		cond_resched();
+
 		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
 			continue;