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mm/mmap: introduce dup_vma_anon() helper 

Create a helper for duplicating the anon vma when adjusting the vma.  This
simplifies the logic of __vma_adjust().

Link: https://lkml.kernel.org/r/20230120162650.984577-47-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett 2023-01-20 11:26:47 -05:00 committed by Andrew Morton
parent cf51e86dfb
commit 04241ffe3f
1 changed files with 40 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
mm/mmap.c
View File

@ -617,6 +617,29 @@ again:
uprobe_mmap(vp->insert);
}
/*
* dup_anon_vma() - Helper function to duplicate anon_vma
* @dst: The destination VMA
* @src: The source VMA
*
* Returns: 0 on success.
*/
static inline int dup_anon_vma(struct vm_area_struct *dst,
struct vm_area_struct *src)
{
/*
* Easily overlooked: when mprotect shifts the boundary, make sure the
* expanding vma has anon_vma set if the shrinking vma had, to cover any
* anon pages imported.
*/
if (src->anon_vma && !dst->anon_vma) {
dst->anon_vma = src->anon_vma;
return anon_vma_clone(dst, src);
}
return 0;
}
/*
* vma_expand - Expand an existing VMA
*
@ -642,15 +665,12 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
struct vma_prepare vp;
if (next && (vma != next) && (end == next->vm_end)) {
remove_next = true;
if (next->anon_vma && !vma->anon_vma) {
int error;
int ret;
vma->anon_vma = next->anon_vma;
error = anon_vma_clone(vma, next);
if (error)
return error;
}
remove_next = true;
ret = dup_anon_vma(vma, next);
if (ret)
return ret;
}
init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL);
@ -739,10 +759,11 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
struct file *file = vma->vm_file;
bool vma_changed = false;
long adjust_next = 0;
struct vm_area_struct *exporter = NULL, *importer = NULL;
struct vma_prepare vma_prep;
if (next) {
int error = 0;
if (end >= next->vm_end) {
/*
* vma expands, overlapping all the next, and
@ -777,15 +798,14 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
end != remove2->vm_end);
}
exporter = next;
importer = vma;
/*
* If next doesn't have anon_vma, import from vma after
* next, if the vma overlaps with it.
*/
if (remove2 != NULL && !next->anon_vma)
exporter = remove2;
if (remove != NULL && !next->anon_vma)
error = dup_anon_vma(vma, remove2);
else
error = dup_anon_vma(vma, remove);
} else if (end > next->vm_start) {
/*
@ -793,9 +813,8 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
* mprotect case 5 shifting the boundary up.
*/
adjust_next = (end - next->vm_start);
exporter = next;
importer = vma;
VM_WARN_ON(expand != importer);
VM_WARN_ON(expand != vma);
error = dup_anon_vma(vma, next);
} else if (end < vma->vm_end) {
/*
* vma shrinks, and !insert tells it's not
@ -803,24 +822,11 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
* mprotect case 4 shifting the boundary down.
*/
adjust_next = -(vma->vm_end - end);
exporter = vma;
importer = next;
VM_WARN_ON(expand != importer);
}
/*
* Easily overlooked: when mprotect shifts the boundary,
* make sure the expanding vma has anon_vma set if the
* shrinking vma had, to cover any anon pages imported.
*/
if (exporter && exporter->anon_vma && !importer->anon_vma) {
int error;
importer->anon_vma = exporter->anon_vma;
error = anon_vma_clone(importer, exporter);
if (error)
return error;
VM_WARN_ON(expand != next);
error = dup_anon_vma(next, vma);
}
if (error)
return error;
}
if (vma_iter_prealloc(vmi))