mm/mmap: simplify vma link and unlink

The file parameter in the __remove_shared_vm_struct is no longer used,
remove it.

These functions vma_link() and mmap_region() have some of the same code,
introduce vma_link_file() helper function to simplify the code.

Link: https://lkml.kernel.org/r/20240110084622.2425927-1-yajun.deng@linux.devSigned-off-by: Yajun Deng <yajun.deng@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/mmap.c

@@ -105,7 +105,7 @@ void vma_set_page_prot(struct vm_area_struct *vma)
  * Requires inode->i_mapping->i_mmap_rwsem
  */
 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
-		struct file *file, struct address_space *mapping)
+				      struct address_space *mapping)
 {
 	if (vma_is_shared_maywrite(vma))
 		mapping_unmap_writable(mapping);
@@ -126,7 +126,7 @@ void unlink_file_vma(struct vm_area_struct *vma)
 	if (file) {
 		struct address_space *mapping = file->f_mapping;
 		i_mmap_lock_write(mapping);
-		__remove_shared_vm_struct(vma, file, mapping);
+		__remove_shared_vm_struct(vma, mapping);
 		i_mmap_unlock_write(mapping);
 	}
 }
@@ -392,26 +392,30 @@ static void __vma_link_file(struct vm_area_struct *vma,
 	flush_dcache_mmap_unlock(mapping);
 }
 
+static void vma_link_file(struct vm_area_struct *vma)
+{
+	struct file *file = vma->vm_file;
+	struct address_space *mapping;
+
+	if (file) {
+		mapping = file->f_mapping;
+		i_mmap_lock_write(mapping);
+		__vma_link_file(vma, mapping);
+		i_mmap_unlock_write(mapping);
+	}
+}
+
 static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
 {
 	VMA_ITERATOR(vmi, mm, 0);
-	struct address_space *mapping = NULL;
 
 	vma_iter_config(&vmi, vma->vm_start, vma->vm_end);
 	if (vma_iter_prealloc(&vmi, vma))
 		return -ENOMEM;
 
 	vma_start_write(vma);
-
 	vma_iter_store(&vmi, vma);
-
-	if (vma->vm_file) {
-		mapping = vma->vm_file->f_mapping;
-		i_mmap_lock_write(mapping);
-		__vma_link_file(vma, mapping);
-		i_mmap_unlock_write(mapping);
-	}
-
+	vma_link_file(vma);
 	mm->map_count++;
 	validate_mm(mm);
 	return 0;
@@ -519,10 +523,9 @@ static inline void vma_complete(struct vma_prepare *vp,
 	}
 
 	if (vp->remove && vp->file) {
-		__remove_shared_vm_struct(vp->remove, vp->file, vp->mapping);
+		__remove_shared_vm_struct(vp->remove, vp->mapping);
 		if (vp->remove2)
-			__remove_shared_vm_struct(vp->remove2, vp->file,
-						  vp->mapping);
+			__remove_shared_vm_struct(vp->remove2, vp->mapping);
 	} else if (vp->insert) {
 		/*
 		 * split_vma has split insert from vma, and needs
@@ -2891,16 +2894,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	vma_start_write(vma);
 	vma_iter_store(&vmi, vma);
 	mm->map_count++;
-	if (vma->vm_file) {
-		i_mmap_lock_write(vma->vm_file->f_mapping);
-		if (vma_is_shared_maywrite(vma))
-			mapping_allow_writable(vma->vm_file->f_mapping);
-
-		flush_dcache_mmap_lock(vma->vm_file->f_mapping);
-		vma_interval_tree_insert(vma, &vma->vm_file->f_mapping->i_mmap);
-		flush_dcache_mmap_unlock(vma->vm_file->f_mapping);
-		i_mmap_unlock_write(vma->vm_file->f_mapping);
-	}
+	vma_link_file(vma);
 
 	/*
 	 * vma_merge() calls khugepaged_enter_vma() either, the below