mm: add temporary vma iterator versions of vma_merge(), split_vma(), and __split_vma()

These wrappers are short-lived in this patch set so that each user can be
converted on its own.  In the end, these functions are renamed in one
commit.

Link: https://lkml.kernel.org/r/20230120162650.984577-15-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm.h

@@ -2843,11 +2843,20 @@ extern struct vm_area_struct *vma_merge(struct mm_struct *,
 	struct vm_area_struct *prev, unsigned long addr, unsigned long end,
 	unsigned long vm_flags, struct anon_vma *, struct file *, pgoff_t,
 	struct mempolicy *, struct vm_userfaultfd_ctx, struct anon_vma_name *);
+extern struct vm_area_struct *vmi_vma_merge(struct vma_iterator *vmi,
+	struct mm_struct *, struct vm_area_struct *prev, unsigned long addr,
+	unsigned long end, unsigned long vm_flags, struct anon_vma *,
+	struct file *, pgoff_t, struct mempolicy *, struct vm_userfaultfd_ctx,
+	struct anon_vma_name *);
 extern struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *);
 extern int __split_vma(struct mm_struct *, struct vm_area_struct *,
-	unsigned long addr, int new_below);
+			       unsigned long addr, int new_below);
+extern int vmi__split_vma(struct vma_iterator *vmi, struct mm_struct *,
+	struct vm_area_struct *, unsigned long addr, int new_below);
 extern int split_vma(struct mm_struct *, struct vm_area_struct *,
 	unsigned long addr, int new_below);
+extern int vmi_split_vma(struct vma_iterator *vmi, struct mm_struct *,
+		struct vm_area_struct *, unsigned long addr, int new_below);
 extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
 extern void unlink_file_vma(struct vm_area_struct *);
 extern struct vm_area_struct *copy_vma(struct vm_area_struct **,

mm/mmap.c

@@ -1091,6 +1091,25 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
 	return res;
 }
 
+struct vm_area_struct *vmi_vma_merge(struct vma_iterator *vmi,
+			struct mm_struct *mm,
+			struct vm_area_struct *prev, unsigned long addr,
+			unsigned long end, unsigned long vm_flags,
+			struct anon_vma *anon_vma, struct file *file,
+			pgoff_t pgoff, struct mempolicy *policy,
+			struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
+			struct anon_vma_name *anon_name)
+{
+	struct vm_area_struct *tmp;
+
+	tmp = vma_merge(mm, prev, addr, end, vm_flags, anon_vma, file, pgoff,
+			policy, vm_userfaultfd_ctx, anon_name);
+	if (tmp)
+		vma_iter_set(vmi, end);
+
+	return tmp;
+}
+
 /*
  * Rough compatibility check to quickly see if it's even worth looking
  * at sharing an anon_vma.
@@ -2276,6 +2295,18 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 	validate_mm_mt(mm);
 	return err;
 }
+int vmi__split_vma(struct vma_iterator *vmi, struct mm_struct *mm,
+		   struct vm_area_struct *vma, unsigned long addr, int new_below)
+{
+	int ret;
+	unsigned long end = vma->vm_end;
+
+	ret = __split_vma(mm, vma, addr, new_below);
+	if (!ret)
+		vma_iter_set(vmi, end);
+
+	return ret;
+}
 
 /*
  * Split a vma into two pieces at address 'addr', a new vma is allocated
@@ -2290,6 +2321,19 @@ int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
 	return __split_vma(mm, vma, addr, new_below);
 }
 
+int vmi_split_vma(struct vma_iterator *vmi, struct mm_struct *mm,
+		  struct vm_area_struct *vma, unsigned long addr, int new_below)
+{
+	int ret;
+	unsigned long end = vma->vm_end;
+
+	ret = split_vma(mm, vma, addr, new_below);
+	if (!ret)
+		vma_iter_set(vmi, end);
+
+	return ret;
+}
+
 static inline int munmap_sidetree(struct vm_area_struct *vma,
 				   struct ma_state *mas_detach)
 {