mm/mmap: move vma_prepare before vma_adjust_trans_huge

vma_prepare() acquires all locks required before VMA modifications.  Move
vma_prepare() before vma_adjust_trans_huge() so that VMA is locked before
any modification.

Link: https://lkml.kernel.org/r/20230227173632.3292573-15-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmap.c

@@ -683,12 +683,12 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	if (vma_iter_prealloc(vmi))
 		goto nomem;
 
+	vma_prepare(&vp);
 	vma_adjust_trans_huge(vma, start, end, 0);
 	/* VMA iterator points to previous, so set to start if necessary */
 	if (vma_iter_addr(vmi) != start)
 		vma_iter_set(vmi, start);
 
-	vma_prepare(&vp);
 	vma->vm_start = start;
 	vma->vm_end = end;
 	vma->vm_pgoff = pgoff;
@@ -723,8 +723,8 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
 		return -ENOMEM;
 
 	init_vma_prep(&vp, vma);
-	vma_adjust_trans_huge(vma, start, end, 0);
 	vma_prepare(&vp);
+	vma_adjust_trans_huge(vma, start, end, 0);
 
 	if (vma->vm_start < start)
 		vma_iter_clear(vmi, vma->vm_start, start);
@@ -1010,12 +1010,12 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 	if (vma_iter_prealloc(vmi))
 		return NULL;
 
-	vma_adjust_trans_huge(vma, vma_start, vma_end, adj_start);
 	init_multi_vma_prep(&vp, vma, adjust, remove, remove2);
 	VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma &&
 		   vp.anon_vma != adjust->anon_vma);
 
 	vma_prepare(&vp);
+	vma_adjust_trans_huge(vma, vma_start, vma_end, adj_start);
 	if (vma_start < vma->vm_start || vma_end > vma->vm_end)
 		vma_expanded = true;
 
@@ -2214,10 +2214,10 @@ int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	if (new->vm_ops && new->vm_ops->open)
 		new->vm_ops->open(new);
 
-	vma_adjust_trans_huge(vma, vma->vm_start, addr, 0);
 	init_vma_prep(&vp, vma);
 	vp.insert = new;
 	vma_prepare(&vp);
+	vma_adjust_trans_huge(vma, vma->vm_start, addr, 0);
 
 	if (new_below) {
 		vma->vm_start = addr;
@@ -2920,9 +2920,9 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
 		if (vma_iter_prealloc(vmi))
 			goto unacct_fail;
 
-		vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
 		init_vma_prep(&vp, vma);
 		vma_prepare(&vp);
+		vma_adjust_trans_huge(vma, vma->vm_start, addr + len, 0);
 		vma->vm_end = addr + len;
 		vm_flags_set(vma, VM_SOFTDIRTY);
 		vma_iter_store(vmi, vma);