[PATCH 35/43] mm/mmap: Refactor locking out of __vma_adjust()

[Liam Howlett]

From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>

Move the locking into vma_prepare() and vma_complete() for use elsewhere

Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
---
 mm/internal.h |  13 +++
 mm/mmap.c     | 231 +++++++++++++++++++++++++++++---------------------
 2 files changed, 149 insertions(+), 95 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index 6b7ef495b56d..4dab33c2f3ed 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -856,4 +856,17 @@ static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
 	return !(vma->vm_flags & VM_SOFTDIRTY);
 }
 
+/*
+ * VMA lock generalization
+ */
+struct vma_prepare {
+	struct vm_area_struct *vma;
+	struct vm_area_struct *adj_next;
+	struct file *file;
+	struct address_space *mapping;
+	struct anon_vma *anon_vma;
+	struct vm_area_struct *insert;
+	struct vm_area_struct *remove;
+	struct vm_area_struct *remove2;
+};
 #endif	/* __MM_INTERNAL_H */
diff --git a/mm/mmap.c b/mm/mmap.c
index 5b5d5d856152..c990a151e45c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -633,6 +633,127 @@ inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	return -ENOMEM;
 }
 
+/*
+ * vma_prepare() - Helper function for handling locking VMAs prior to altering
+ * @vp: The initialized vma_prepare struct
+ */
+static inline void vma_prepare(struct vma_prepare *vp)
+{
+	if (vp->file) {
+		uprobe_munmap(vp->vma, vp->vma->vm_start, vp->vma->vm_end);
+
+		if (vp->adj_next)
+			uprobe_munmap(vp->adj_next, vp->adj_next->vm_start,
+				      vp->adj_next->vm_end);
+
+		i_mmap_lock_write(vp->mapping);
+		if (vp->insert && vp->insert->vm_file) {
+			/*
+			 * Put into interval tree now, so instantiated pages
+			 * are visible to arm/parisc __flush_dcache_page
+			 * throughout; but we cannot insert into address
+			 * space until vma start or end is updated.
+			 */
+			__vma_link_file(vp->insert,
+					vp->insert->vm_file->f_mapping);
+		}
+	}
+
+	if (vp->anon_vma) {
+		anon_vma_lock_write(vp->anon_vma);
+		anon_vma_interval_tree_pre_update_vma(vp->vma);
+		if (vp->adj_next)
+			anon_vma_interval_tree_pre_update_vma(vp->adj_next);
+	}
+
+	if (vp->file) {
+		flush_dcache_mmap_lock(vp->mapping);
+		vma_interval_tree_remove(vp->vma, &vp->mapping->i_mmap);
+		if (vp->adj_next)
+			vma_interval_tree_remove(vp->adj_next,
+						 &vp->mapping->i_mmap);
+	}
+
+}
+
+/*
+ * vma_complete- Helper function for handling the unlocking after altering VMAs,
+ * or for inserting a VMA.
+ *
+ * @vp: The vma_prepare struct
+ * @vmi: The vma iterator
+ * @mm: The mm_struct
+ */
+static inline void vma_complete(struct vma_prepare *vp,
+				struct vma_iterator *vmi, struct mm_struct *mm)
+{
+	if (vp->file) {
+		if (vp->adj_next)
+			vma_interval_tree_insert(vp->adj_next,
+						 &vp->mapping->i_mmap);
+		vma_interval_tree_insert(vp->vma, &vp->mapping->i_mmap);
+		flush_dcache_mmap_unlock(vp->mapping);
+	}
+
+	if (vp->remove && vp->file) {
+		__remove_shared_vm_struct(vp->remove, vp->file, vp->mapping);
+		if (vp->remove2)
+			__remove_shared_vm_struct(vp->remove2, vp->file,
+						  vp->mapping);
+	} else if (vp->insert) {
+		/*
+		 * split_vma has split insert from vma, and needs
+		 * us to insert it before dropping the locks
+		 * (it may either follow vma or precede it).
+		 */
+		vma_iter_store(vmi, vp->insert);
+		mm->map_count++;
+	}
+
+	if (vp->anon_vma) {
+		anon_vma_interval_tree_post_update_vma(vp->vma);
+		if (vp->adj_next)
+			anon_vma_interval_tree_post_update_vma(vp->adj_next);
+		anon_vma_unlock_write(vp->anon_vma);
+	}
+
+	if (vp->file) {
+		i_mmap_unlock_write(vp->mapping);
+		uprobe_mmap(vp->vma);
+
+		if (vp->adj_next)
+			uprobe_mmap(vp->adj_next);
+	}
+
+	if (vp->remove) {
+again:
+		if (vp->file) {
+			uprobe_munmap(vp->remove, vp->remove->vm_start,
+				      vp->remove->vm_end);
+			fput(vp->file);
+		}
+		if (vp->remove->anon_vma)
+			anon_vma_merge(vp->vma, vp->remove);
+		mm->map_count--;
+		mpol_put(vma_policy(vp->remove));
+		if (!vp->remove2)
+			WARN_ON_ONCE(vp->vma->vm_end < vp->remove->vm_end);
+		vm_area_free(vp->remove);
+
+		/*
+		 * In mprotect's case 6 (see comments on vma_merge),
+		 * we must remove next_next too.
+		 */
+		if (vp->remove2) {
+			vp->remove = vp->remove2;
+			vp->remove2 = NULL;
+			goto again;
+		}
+	}
+	if (vp->insert && vp->file)
+		uprobe_mmap(vp->insert);
+}
+
 /*
  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
  * is already present in an i_mmap tree without adjusting the tree.
@@ -648,14 +769,13 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	struct vm_area_struct *next_next = NULL;	/* uninit var warning */
 	struct vm_area_struct *next = find_vma(mm, vma->vm_end);
 	struct vm_area_struct *orig_vma = vma;
-	struct address_space *mapping = NULL;
-	struct rb_root_cached *root = NULL;
 	struct anon_vma *anon_vma = NULL;
 	struct file *file = vma->vm_file;
 	bool vma_changed = false;
 	long adjust_next = 0;
 	int remove_next = 0;
 	struct vm_area_struct *exporter = NULL, *importer = NULL;
+	struct vma_prepare vma_prep;
 
 	if (next && !insert) {
 		if (end >= next->vm_end) {
@@ -751,39 +871,22 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
 			   anon_vma != next->anon_vma);
 
 	vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
-	if (file) {
-		mapping = file->f_mapping;
-		root = &mapping->i_mmap;
-		uprobe_munmap(vma, vma->vm_start, vma->vm_end);
-
-		if (adjust_next)
-			uprobe_munmap(next, next->vm_start, next->vm_end);
-
-		i_mmap_lock_write(mapping);
-		if (insert && insert->vm_file) {
-			/*
-			 * Put into interval tree now, so instantiated pages
-			 * are visible to arm/parisc __flush_dcache_page
-			 * throughout; but we cannot insert into address
-			 * space until vma start or end is updated.
-			 */
-			__vma_link_file(insert, insert->vm_file->f_mapping);
-		}
-	}
 
-	if (anon_vma) {
-		anon_vma_lock_write(anon_vma);
-		anon_vma_interval_tree_pre_update_vma(vma);
-		if (adjust_next)
-			anon_vma_interval_tree_pre_update_vma(next);
+	memset(&vma_prep, 0, sizeof(vma_prep));
+	vma_prep.vma = vma;
+	vma_prep.anon_vma = anon_vma;
+	vma_prep.file = file;
+	if (adjust_next)
+		vma_prep.adj_next = next;
+	if (file)
+		vma_prep.mapping = file->f_mapping;
+	vma_prep.insert = insert;
+	if (remove_next) {
+		vma_prep.remove = next;
+		vma_prep.remove2 = next_next;
 	}
 
-	if (file) {
-		flush_dcache_mmap_lock(mapping);
-		vma_interval_tree_remove(vma, root);
-		if (adjust_next)
-			vma_interval_tree_remove(next, root);
-	}
+	vma_prepare(&vma_prep);
 
 	if (start != vma->vm_start) {
 		if (vma->vm_start < start) {
@@ -821,69 +924,7 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
 		vma_iter_store(vmi, next);
 	}
 
-	if (file) {
-		if (adjust_next)
-			vma_interval_tree_insert(next, root);
-		vma_interval_tree_insert(vma, root);
-		flush_dcache_mmap_unlock(mapping);
-	}
-
-	if (remove_next && file) {
-		__remove_shared_vm_struct(next, file, mapping);
-		if (remove_next == 2)
-			__remove_shared_vm_struct(next_next, file, mapping);
-	} else if (insert) {
-		/*
-		 * split_vma has split insert from vma, and needs
-		 * us to insert it before dropping the locks
-		 * (it may either follow vma or precede it).
-		 */
-		vma_iter_store(vmi, insert);
-		mm->map_count++;
-	}
-
-	if (anon_vma) {
-		anon_vma_interval_tree_post_update_vma(vma);
-		if (adjust_next)
-			anon_vma_interval_tree_post_update_vma(next);
-		anon_vma_unlock_write(anon_vma);
-	}
-
-	if (file) {
-		i_mmap_unlock_write(mapping);
-		uprobe_mmap(vma);
-
-		if (adjust_next)
-			uprobe_mmap(next);
-	}
-
-	if (remove_next) {
-again:
-		if (file) {
-			uprobe_munmap(next, next->vm_start, next->vm_end);
-			fput(file);
-		}
-		if (next->anon_vma)
-			anon_vma_merge(vma, next);
-		mm->map_count--;
-		mpol_put(vma_policy(next));
-		if (remove_next != 2)
-			BUG_ON(vma->vm_end < next->vm_end);
-		vm_area_free(next);
-
-		/*
-		 * In mprotect's case 6 (see comments on vma_merge),
-		 * we must remove next_next too.
-		 */
-		if (remove_next == 2) {
-			remove_next = 1;
-			next = next_next;
-			goto again;
-		}
-	}
-	if (insert && file)
-		uprobe_mmap(insert);
-
+	vma_complete(&vma_prep, vmi, mm);
 	vma_iter_free(vmi);
 	validate_mm(mm);
 
-- 
2.35.1