Commit 9303d3e1 authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

mm/mmap: use vma_prepare() and vma_complete() in vma_expand() 

Use the new locking functions for vma_expand().  This reduces code
duplication.

At the same time change VM_BUG_ON() to VM_WARN_ON()

Link: https://lkml.kernel.org/r/20230120162650.984577-42-Liam.Howlett@oracle.com


Signed-off-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 440703e0

mm/mmap.c

+72 −116
Original line number Diff line number Diff line
@@ -457,122 +457,6 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma) 
	return 0;

}



/*

 * vma_expand - Expand an existing VMA

 *

 * @mas: The maple state

 * @vma: The vma to expand

 * @start: The start of the vma

 * @end: The exclusive end of the vma

 * @pgoff: The page offset of vma

 * @next: The current of next vma.

 *

 * Expand @vma to @start and @end.  Can expand off the start and end.  Will

 * expand over @next if it's different from @vma and @end == @next->vm_end.

 * Checking if the @vma can expand and merge with @next needs to be handled by

 * the caller.

 *

 * Returns: 0 on success

 */

inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,

		      unsigned long start, unsigned long end, pgoff_t pgoff,

		      struct vm_area_struct *next)

{

	struct mm_struct *mm = vma->vm_mm;

	struct address_space *mapping = NULL;

	struct rb_root_cached *root = NULL;

	struct anon_vma *anon_vma = vma->anon_vma;

	struct file *file = vma->vm_file;

	bool remove_next = false;



	if (next && (vma != next) && (end == next->vm_end)) {

		remove_next = true;

		if (next->anon_vma && !vma->anon_vma) {

			int error;



			anon_vma = next->anon_vma;

			vma->anon_vma = anon_vma;

			error = anon_vma_clone(vma, next);

			if (error)

				return error;

		}

	}



	/* Not merging but overwriting any part of next is not handled. */

	VM_BUG_ON(next && !remove_next && next != vma && end > next->vm_start);

	/* Only handles expanding */

	VM_BUG_ON(vma->vm_start < start || vma->vm_end > end);



	if (vma_iter_prealloc(vmi))

		goto nomem;



	vma_adjust_trans_huge(vma, start, end, 0);



	if (file) {

		mapping = file->f_mapping;

		root = &mapping->i_mmap;

		uprobe_munmap(vma, vma->vm_start, vma->vm_end);

		i_mmap_lock_write(mapping);

	}



	if (anon_vma) {

		anon_vma_lock_write(anon_vma);

		anon_vma_interval_tree_pre_update_vma(vma);

	}



	if (file) {

		flush_dcache_mmap_lock(mapping);

		vma_interval_tree_remove(vma, root);

	}



	/* VMA iterator points to previous, so set to start if necessary */

	if (vma_iter_addr(vmi) != start)

		vma_iter_set(vmi, start);



	vma->vm_start = start;

	vma->vm_end = end;

	vma->vm_pgoff = pgoff;

	vma_iter_store(vmi, vma);



	if (file) {

		vma_interval_tree_insert(vma, root);

		flush_dcache_mmap_unlock(mapping);

	}



	/* Expanding over the next vma */

	if (remove_next && file) {

		__remove_shared_vm_struct(next, file, mapping);

	}



	if (anon_vma) {

		anon_vma_interval_tree_post_update_vma(vma);

		anon_vma_unlock_write(anon_vma);

	}



	if (file) {

		i_mmap_unlock_write(mapping);

		uprobe_mmap(vma);

	}



	if (remove_next) {

		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));

		vm_area_free(next);

	}



	validate_mm(mm);

	return 0;



nomem:

	return -ENOMEM;

}



/*

 * vma_prepare() - Helper function for handling locking VMAs prior to altering

 * @vp: The initialized vma_prepare struct
@@ -694,6 +578,78 @@ static inline void vma_complete(struct vma_prepare *vp, 
		uprobe_mmap(vp->insert);

}



/*

 * vma_expand - Expand an existing VMA

 *

 * @vmi: The vma iterator

 * @vma: The vma to expand

 * @start: The start of the vma

 * @end: The exclusive end of the vma

 * @pgoff: The page offset of vma

 * @next: The current of next vma.

 *

 * Expand @vma to @start and @end.  Can expand off the start and end.  Will

 * expand over @next if it's different from @vma and @end == @next->vm_end.

 * Checking if the @vma can expand and merge with @next needs to be handled by

 * the caller.

 *

 * Returns: 0 on success

 */

inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,

		      unsigned long start, unsigned long end, pgoff_t pgoff,

		      struct vm_area_struct *next)

{

	struct vma_prepare vp;



	memset(&vp, 0, sizeof(vp));

	vp.vma = vma;

	vp.anon_vma = vma->anon_vma;

	if (next && (vma != next) && (end == next->vm_end)) {

		vp.remove = next;

		if (next->anon_vma && !vma->anon_vma) {

			int error;



			vp.anon_vma = next->anon_vma;

			vma->anon_vma = next->anon_vma;

			error = anon_vma_clone(vma, next);

			if (error)

				return error;

		}

	}



	/* Not merging but overwriting any part of next is not handled. */

	VM_WARN_ON(next && !vp.remove &&

		  next != vma && end > next->vm_start);

	/* Only handles expanding */

	VM_WARN_ON(vma->vm_start < start || vma->vm_end > end);



	if (vma_iter_prealloc(vmi))

		goto nomem;



	vma_adjust_trans_huge(vma, start, end, 0);



	vp.file = vma->vm_file;

	if (vp.file)

		vp.mapping = vp.file->f_mapping;



	/* 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;

	/* Note: mas must be pointing to the expanding VMA */

	vma_iter_store(vmi, vma);



	vma_complete(&vp, vmi, vma->vm_mm);

	validate_mm(vma->vm_mm);

	return 0;



nomem:

	return -ENOMEM;

}

/*

 * 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.