mm: don't use __vma_adjust() in __split_vma()

Use the abstracted locking and maple tree operations.  Since __split_vma()
is the only user of the __vma_adjust() function to use the insert
argument, drop that argument.  Remove the NULL passed through from
fs/exec's shift_arg_pages() and mremap() at the same time.

Link: https://lkml.kernel.org/r/20230120162650.984577-44-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 56 insertions, 64 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index e259b33fcb52..3d08d7d243f0 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -691,7 +691,7 @@ nomem:
  */
 int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	unsigned long start, unsigned long end, pgoff_t pgoff,
-	struct vm_area_struct *insert, struct vm_area_struct *expand)
+	struct vm_area_struct *expand)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct vm_area_struct *remove2 = NULL;
@@ -704,7 +704,7 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	struct vm_area_struct *exporter = NULL, *importer = NULL;
 	struct vma_prepare vma_prep;
 
-	if (next && !insert) {
+	if (next) {
 		if (end >= next->vm_end) {
 			/*
 			 * vma expands, overlapping all the next, and
@@ -795,39 +795,25 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	VM_WARN_ON(vma_prep.anon_vma && adjust_next && next->anon_vma &&
 		   vma_prep.anon_vma != next->anon_vma);
 
-	vma_prep.insert = insert;
 	vma_prepare(&vma_prep);
 
-	if (start != vma->vm_start) {
-		if (vma->vm_start < start) {
-			if (!insert || (insert->vm_end != start)) {
-				vma_iter_clear(vmi, vma->vm_start, start);
-				vma_iter_set(vmi, start);
-				VM_WARN_ON(insert && insert->vm_start > vma->vm_start);
-			}
-		} else {
-			vma_changed = true;
-		}
-		vma->vm_start = start;
-	}
-	if (end != vma->vm_end) {
-		if (vma->vm_end > end) {
-			if (!insert || (insert->vm_start != end)) {
-				vma_iter_clear(vmi, end, vma->vm_end);
-				vma_iter_set(vmi, vma->vm_end);
-				VM_WARN_ON(insert &&
-					   insert->vm_end < vma->vm_end);
-			}
-		} else {
-			vma_changed = true;
-		}
-		vma->vm_end = end;
-	}
+	if (vma->vm_start < start)
+		vma_iter_clear(vmi, vma->vm_start, start);
+	else if (start != vma->vm_start)
+		vma_changed = true;
+
+	if (vma->vm_end > end)
+		vma_iter_clear(vmi, end, vma->vm_end);
+	else if (end != vma->vm_end)
+		vma_changed = true;
+
+	vma->vm_start = start;
+	vma->vm_end = end;
+	vma->vm_pgoff = pgoff;
 
 	if (vma_changed)
 		vma_iter_store(vmi, vma);
 
-	vma->vm_pgoff = pgoff;
 	if (adjust_next) {
 		next->vm_start += adjust_next;
 		next->vm_pgoff += adjust_next >> PAGE_SHIFT;
@@ -846,9 +832,9 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
  * per-vma resources, so we don't attempt to merge those.
  */
 static inline int is_mergeable_vma(struct vm_area_struct *vma,
-				struct file *file, unsigned long vm_flags,
-				struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
-				struct anon_vma_name *anon_name)
+				   struct file *file, unsigned long vm_flags,
+				   struct vm_userfaultfd_ctx vm_userfaultfd_ctx,
+				   struct anon_vma_name *anon_name)
 {
 	/*
 	 * VM_SOFTDIRTY should not prevent from VMA merging, if we
@@ -1030,20 +1016,19 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 			is_mergeable_anon_vma(prev->anon_vma,
 				next->anon_vma, NULL)) {	 /* cases 1, 6 */
 		err = __vma_adjust(vmi, prev, prev->vm_start,
-					next->vm_end, prev->vm_pgoff, NULL,
-					prev);
+					next->vm_end, prev->vm_pgoff, prev);
 		res = prev;
 	} else if (merge_prev) {			/* cases 2, 5, 7 */
 		err = __vma_adjust(vmi, prev, prev->vm_start,
-					end, prev->vm_pgoff, NULL, prev);
+					end, prev->vm_pgoff, prev);
 		res = prev;
 	} else if (merge_next) {
 		if (prev && addr < prev->vm_end)	/* case 4 */
 			err = __vma_adjust(vmi, prev, prev->vm_start,
-					addr, prev->vm_pgoff, NULL, next);
+					addr, prev->vm_pgoff, next);
 		else					/* cases 3, 8 */
 			err = __vma_adjust(vmi, mid, addr, next->vm_end,
-					next->vm_pgoff - pglen, NULL, next);
+					next->vm_pgoff - pglen, next);
 		res = next;
 	}
 
@@ -2187,11 +2172,15 @@ static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
 int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 		unsigned long addr, int new_below)
 {
+	struct vma_prepare vp;
 	struct vm_area_struct *new;
 	int err;
 
 	validate_mm_mt(vma->vm_mm);
 
+	WARN_ON(vma->vm_start >= addr);
+	WARN_ON(vma->vm_end <= addr);
+
 	if (vma->vm_ops && vma->vm_ops->may_split) {
 		err = vma->vm_ops->may_split(vma, addr);
 		if (err)
@@ -2202,16 +2191,20 @@ int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	if (!new)
 		return -ENOMEM;
 
-	if (new_below)
+	err = -ENOMEM;
+	if (vma_iter_prealloc(vmi))
+		goto out_free_vma;
+
+	if (new_below) {
 		new->vm_end = addr;
-	else {
+	} else {
 		new->vm_start = addr;
 		new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
 	}
 
 	err = vma_dup_policy(vma, new);
 	if (err)
-		goto out_free_vma;
+		goto out_free_vmi;
 
 	err = anon_vma_clone(new, vma);
 	if (err)
@@ -2223,33 +2216,32 @@ 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);
 
-	if (new_below)
-		err = vma_adjust(vmi, vma, addr, vma->vm_end,
-			vma->vm_pgoff + ((addr - new->vm_start) >> PAGE_SHIFT),
-			new);
-	else
-		err = vma_adjust(vmi, vma, vma->vm_start, addr, vma->vm_pgoff,
-				 new);
+	vma_adjust_trans_huge(vma, vma->vm_start, addr, 0);
+	init_vma_prep(&vp, vma);
+	vp.insert = new;
+	vma_prepare(&vp);
 
-	/* Success. */
-	if (!err) {
-		if (new_below)
-			vma_next(vmi);
-		return 0;
+	if (new_below) {
+		vma->vm_start = addr;
+		vma->vm_pgoff += (addr - new->vm_start) >> PAGE_SHIFT;
+	} else {
+		vma->vm_end = addr;
 	}
 
-	/* Avoid vm accounting in close() operation */
-	new->vm_start = new->vm_end;
-	new->vm_pgoff = 0;
-	/* Clean everything up if vma_adjust failed. */
-	if (new->vm_ops && new->vm_ops->close)
-		new->vm_ops->close(new);
-	if (new->vm_file)
-		fput(new->vm_file);
-	unlink_anon_vmas(new);
- out_free_mpol:
+	/* vma_complete stores the new vma */
+	vma_complete(&vp, vmi, vma->vm_mm);
+
+	/* Success. */
+	if (new_below)
+		vma_next(vmi);
+	validate_mm_mt(vma->vm_mm);
+	return 0;
+
+out_free_mpol:
 	mpol_put(vma_policy(new));
- out_free_vma:
+out_free_vmi:
+	vma_iter_free(vmi);
+out_free_vma:
 	vm_area_free(new);
 	validate_mm_mt(vma->vm_mm);
 	return err;
diff --git a/mm/mremap.c b/mm/mremap.c
index 6c7f49ab7d19..b98185f48ba5 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -1054,7 +1054,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
 					vma->vm_file, extension_pgoff, vma_policy(vma),
 					vma->vm_userfaultfd_ctx, anon_vma_name(vma));
 			} else if (vma_adjust(&vmi, vma, vma->vm_start,
-					addr + new_len, vma->vm_pgoff, NULL)) {
+					addr + new_len, vma->vm_pgoff)) {
 				vma = NULL;
 			}
 			if (!vma) {