Commit cf51e86d authored by Liam R. Howlett's avatar Liam R. Howlett Committed by Andrew Morton
Browse files

mm/mmap: don't use __vma_adjust() in shift_arg_pages() 

Introduce shrink_vma() which uses the vma_prepare() and vma_complete()
functions to reduce the vma coverage.

Convert shift_arg_pages() to use expand_vma() and the new shrink_vma()
function.  Remove support from __vma_adjust() to reduce a vma size since
shift_arg_pages() is the only user that shrinks a VMA in this way.

Link: https://lkml.kernel.org/r/20230120162650.984577-46-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 7c9813e8

fs/exec.c

+2 −2
Original line number Diff line number Diff line
@@ -699,7 +699,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 
	/*

	 * cover the whole range: [new_start, old_end)

	 */

	if (vma_adjust(&vmi, vma, new_start, old_end, vma->vm_pgoff))

	if (vma_expand(&vmi, vma, new_start, old_end, vma->vm_pgoff, NULL))

		return -ENOMEM;



	/*
@@ -733,7 +733,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) 


	vma_prev(&vmi);

	/* Shrink the vma to just the new range */

	return vma_adjust(&vmi, vma, new_start, new_end, vma->vm_pgoff);

	return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff);

}



/*

include/linux/mm.h

+2 −8
Original line number Diff line number Diff line
@@ -2831,17 +2831,11 @@ void anon_vma_interval_tree_verify(struct anon_vma_chain *node); 


/* mmap.c */

extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin);

extern 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 *expand);

static inline int vma_adjust(struct vma_iterator *vmi,

	struct vm_area_struct *vma, unsigned long start, unsigned long end,

	pgoff_t pgoff)

{

	return __vma_adjust(vmi, vma, start, end, pgoff, NULL);

}

extern 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);

extern int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,

		       unsigned long start, unsigned long end, pgoff_t pgoff);

extern struct vm_area_struct *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 *,

mm/mmap.c

+43 −9
Original line number Diff line number Diff line
@@ -682,6 +682,44 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma, 
nomem:

	return -ENOMEM;

}



/*

 * vma_shrink() - Reduce an existing VMAs memory area

 * @vmi: The vma iterator

 * @vma: The VMA to modify

 * @start: The new start

 * @end: The new end

 *

 * Returns: 0 on success, -ENOMEM otherwise

 */

int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,

	       unsigned long start, unsigned long end, pgoff_t pgoff)

{

	struct vma_prepare vp;



	WARN_ON((vma->vm_start != start) && (vma->vm_end != end));



	if (vma_iter_prealloc(vmi))

		return -ENOMEM;



	init_vma_prep(&vp, vma);

	vma_adjust_trans_huge(vma, start, end, 0);

	vma_prepare(&vp);



	if (vma->vm_start < start)

		vma_iter_clear(vmi, vma->vm_start, start);



	if (vma->vm_end > end)

		vma_iter_clear(vmi, end, vma->vm_end);



	vma->vm_start = start;

	vma->vm_end = end;

	vma->vm_pgoff = pgoff;

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

	validate_mm(vma->vm_mm);

	return 0;

}



/*

 * 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.
@@ -797,14 +835,7 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, 


	vma_prepare(&vma_prep);



	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)

	if (start < vma->vm_start || end > vma->vm_end)

		vma_changed = true;



	vma->vm_start = start;
@@ -817,8 +848,11 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma, 
	if (adjust_next) {

		next->vm_start += adjust_next;

		next->vm_pgoff += adjust_next >> PAGE_SHIFT;

		if (adjust_next < 0) {

			WARN_ON_ONCE(vma_changed);

			vma_iter_store(vmi, next);

		}

	}



	vma_complete(&vma_prep, vmi, mm);

	vma_iter_free(vmi);