[PATCH v3 42/48] mm/mmap: Introduce init_vma_prep() and init_multi_vma_prep()

Liam Howlett
2023-01-17T04:14:19Z

Add init_vma_prep() and init_multi_vma_prep() to set up the struct
vma_prepare. This is to abstract the locking when adjusting the VMAs.

Also change __vma_adjust() variable remove_next int in favour of a
pointer to the VMA to remove. Rename next_next to remove2 since this
better reflects its use.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
mm/mmap.c | 108 ++++++++++++++++++++++++++++++------------------------
1 file changed, 61 insertions(+), 47 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 2ea7bf439f4f..b28f3416b60a 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -460,6 +460,45 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
return 0;
}

+/*
+ * init_multi_vma_prep() - Initializer for struct vma_prepare
+ * @vp: The vma_prepare struct
+ * @vma: The vma that will be altered once locked
+ * @next: The next vma if it is to be adjusted
+ * @remove: The first vma to be removed
+ * @remove2: The second vma to be removed
+ */
+static inline void init_multi_vma_prep(struct vma_prepare *vp,
+ struct vm_area_struct *vma, struct vm_area_struct *next,
+ struct vm_area_struct *remove, struct vm_area_struct *remove2)
+{
+ memset(vp, 0, sizeof(struct vma_prepare));
+ vp->vma = vma;
+ vp->anon_vma = vma->anon_vma;
+ vp->remove = remove;
+ vp->remove2 = remove2;
+ vp->adj_next = next;
+ if (!vp->anon_vma && next)
+ vp->anon_vma = next->anon_vma;
+
+ vp->file = vma->vm_file;
+ if (vp->file)
+ vp->mapping = vma->vm_file->f_mapping;
+
+}
+
+/*
+ * init_vma_prep() - Initializer wrapper for vma_prepare struct
+ * @vp: The vma_prepare struct
+ * @vma: The vma that will be altered once locked
+ */
+static inline void init_vma_prep(struct vma_prepare *vp,
+ struct vm_area_struct *vma)
+{
+ init_multi_vma_prep(vp, vma, NULL, NULL, NULL);
+}
+
+
/*
* vma_prepare() - Helper function for handling locking VMAs prior to altering
* @vp: The initialized vma_prepare struct
@@ -569,7 +608,7 @@ static inline void vma_complete(struct vma_prepare *vp,

/*
* In mprotect's case 6 (see comments on vma_merge),
- * we must remove next_next too.
+ * we must remove the one after next as well.
*/
if (vp->remove2) {
vp->remove = vp->remove2;
@@ -603,17 +642,14 @@ inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
struct vm_area_struct *next)

{
+ bool remove_next = false;
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;
+ remove_next = true;
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)
@@ -621,6 +657,7 @@ inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
}
}

+ init_multi_vma_prep(&vp, vma, NULL, remove_next ? next : NULL, NULL);
/* Not merging but overwriting any part of next is not handled. */
VM_WARN_ON(next && !vp.remove &&
next != vma && end > next->vm_start);
@@ -631,11 +668,6 @@ inline int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
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);
@@ -666,14 +698,13 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
struct vm_area_struct *insert, struct vm_area_struct *expand)
{
struct mm_struct *mm = vma->vm_mm;
- struct vm_area_struct *next_next = NULL; /* uninit var warning */
+ struct vm_area_struct *remove2 = NULL;
+ struct vm_area_struct *remove = NULL;
struct vm_area_struct *next = find_vma(mm, vma->vm_end);
struct vm_area_struct *orig_vma = vma;
- 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;

@@ -692,25 +723,24 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
*/
VM_WARN_ON(end != next->vm_end);
/*
- * remove_next == 3 means we're
- * removing "vma" and that to do so we
+ * we're removing "vma" and that to do so we
* swapped "vma" and "next".
*/
- remove_next = 3;
VM_WARN_ON(file != next->vm_file);
swap(vma, next);
+ remove = next;
} else {
VM_WARN_ON(expand != vma);
/*
- * case 1, 6, 7, remove_next == 2 is case 6,
- * remove_next == 1 is case 1 or 7.
+ * case 1, 6, 7, remove next.
+ * case 6 also removes the one beyond next
*/
- remove_next = 1 + (end > next->vm_end);
- if (remove_next == 2)
- next_next = find_vma(mm, next->vm_end);
+ remove = next;
+ if (end > next->vm_end)
+ remove2 = find_vma(mm, next->vm_end);

- VM_WARN_ON(remove_next == 2 &&
- end != next_next->vm_end);
+ VM_WARN_ON(remove2 != NULL &&
+ end != remove2->vm_end);
}

exporter = next;
@@ -720,8 +750,8 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
* If next doesn't have anon_vma, import from vma after
* next, if the vma overlaps with it.
*/
- if (remove_next == 2 && !next->anon_vma)
- exporter = next_next;
+ if (remove2 != NULL && !next->anon_vma)
+ exporter = remove2;

} else if (end > next->vm_start) {
/*
@@ -762,30 +792,14 @@ int __vma_adjust(struct vma_iterator *vmi, struct vm_area_struct *vma,
if (vma_iter_prealloc(vmi, vma))
return -ENOMEM;

- anon_vma = vma->anon_vma;
- if (!anon_vma && adjust_next)
- anon_vma = next->anon_vma;
-
- if (anon_vma)
- VM_WARN_ON(adjust_next && next->anon_vma &&
- anon_vma != next->anon_vma);
-
vma_adjust_trans_huge(orig_vma, start, end, adjust_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;
- }
+ init_multi_vma_prep(&vma_prep, vma, adjust_next ? next : NULL, remove,
+ remove2);
+ 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) {
--
2.35.1