[PATCH 04/10] mm: abstract parameters for vma_expand/shrink()

Lorenzo Stoakes
2024-08-05T12:14:39Z

Equally use struct vma_merge_struct to abstract parameters for VMA
expansion and shrinking.

This leads the way to further refactoring and de-duplication by
standardising the interface.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
mm/mmap.c | 30 +++++++++++--------
mm/vma.c | 66 ++++++++++++++++++-----------------------
mm/vma.h | 8 ++---
tools/testing/vma/vma.c | 18 +++++++++--
4 files changed, 65 insertions(+), 57 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 721ced6e37b0..04145347c245 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1367,7 +1367,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
pgoff_t pglen = len >> PAGE_SHIFT;
unsigned long charged = 0;
unsigned long end = addr + len;
- unsigned long merge_start = addr, merge_end = end;
bool writable_file_mapping = false;
int error;
VMA_ITERATOR(vmi, mm, addr);
@@ -1423,28 +1422,26 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
/* Attempt to expand an old mapping */
/* Check next */
if (next && next->vm_start == end && can_vma_merge_before(&vmg)) {
- merge_end = next->vm_end;
- vma = next;
+ /* We can adjust this as can_vma_merge_after() doesn't touch */
+ vmg.end = next->vm_end;
+ vma = vmg.vma = next;
vmg.pgoff = next->vm_pgoff - pglen;
- }

- if (vma) {
+ /* We may merge our NULL anon_vma with non-NULL in next. */
vmg.anon_vma = vma->anon_vma;
- vmg.uffd_ctx = vma->vm_userfaultfd_ctx;
}

/* Check prev */
if (prev && prev->vm_end == addr && can_vma_merge_after(&vmg)) {
- merge_start = prev->vm_start;
- vma = prev;
+ vmg.start = prev->vm_start;
+ vma = vmg.vma = prev;
vmg.pgoff = prev->vm_pgoff;
} else if (prev) {
vma_iter_next_range(&vmi);
}

/* Actually expand, if possible */
- if (vma &&
- !vma_expand(&vmi, vma, merge_start, merge_end, vmg.pgoff, next)) {
+ if (vma && !vma_expand(&vmg)) {
khugepaged_enter_vma(vma, vm_flags);
goto expanded;
}
@@ -2359,6 +2356,13 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift)
VMA_ITERATOR(vmi, mm, new_start);
struct vm_area_struct *next;
struct mmu_gather tlb;
+ struct vma_merge_struct vmg = {
+ .vmi = &vmi,
+ .vma = vma,
+ .start = new_start,
+ .end = old_end,
+ .pgoff = vma->vm_pgoff,
+ };

BUG_ON(new_start > new_end);

@@ -2373,7 +2377,7 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift)
/*
* cover the whole range: [new_start, old_end)
*/
- if (vma_expand(&vmi, vma, new_start, old_end, vma->vm_pgoff, NULL))
+ if (vma_expand(&vmg))
return -ENOMEM;

/*
@@ -2406,6 +2410,8 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift)
tlb_finish_mmu(&tlb);

vma_prev(&vmi);
+ vmg.end = new_end;
+
/* Shrink the vma to just the new range */
- return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff);
+ return vma_shrink(&vmg);
}
diff --git a/mm/vma.c b/mm/vma.c
index b452b472a085..3d6ce04f1b9c 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -489,30 +489,25 @@ void validate_mm(struct mm_struct *mm)
/*
* 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.
+ * @vmg: Describes a VMA expansion operation.
*
- * 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.
+ * Expand @vma to vmg->start and vmg->end. Can expand off the start and end.
+ * Will expand over vmg->next if it's different from vmg->vma and vmg->end ==
+ * vmg->next->vm_end. Checking if the vmg->vma can expand and merge with
+ * vmg->next needs to be handled by the caller.
*
* Returns: 0 on success
*/
-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)
+int vma_expand(struct vma_merge_struct *vmg)
{
struct vm_area_struct *anon_dup = NULL;
bool remove_next = false;
+ struct vm_area_struct *vma = vmg->vma;
+ struct vm_area_struct *next = vmg->next;
struct vma_prepare vp;

vma_start_write(vma);
- if (next && (vma != next) && (end == next->vm_end)) {
+ if (next && (vma != next) && (vmg->end == next->vm_end)) {
int ret;

remove_next = true;
@@ -525,21 +520,21 @@ 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);
+ next != vma && vmg->end > next->vm_start);
/* Only handles expanding */
- VM_WARN_ON(vma->vm_start < start || vma->vm_end > end);
+ VM_WARN_ON(vma->vm_start < vmg->start || vma->vm_end > vmg->end);

/* Note: vma iterator must be pointing to 'start' */
- vma_iter_config(vmi, start, end);
- if (vma_iter_prealloc(vmi, vma))
+ vma_iter_config(vmg->vmi, vmg->start, vmg->end);
+ if (vma_iter_prealloc(vmg->vmi, vma))
goto nomem;

vma_prepare(&vp);
- vma_adjust_trans_huge(vma, start, end, 0);
- vma_set_range(vma, start, end, pgoff);
- vma_iter_store(vmi, vma);
+ vma_adjust_trans_huge(vma, vmg->start, vmg->end, 0);
+ vma_set_range(vma, vmg->start, vmg->end, vmg->pgoff);
+ vma_iter_store(vmg->vmi, vma);

- vma_complete(&vp, vmi, vma->vm_mm);
+ vma_complete(&vp, vmg->vmi, vma->vm_mm);
return 0;

nomem:
@@ -550,37 +545,34 @@ int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,

/*
* 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
+ * @vmg: Describes a VMA shrink operation.
*
* 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)
+int vma_shrink(struct vma_merge_struct *vmg)
{
+ struct vm_area_struct *vma = vmg->vma;
struct vma_prepare vp;

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

- if (vma->vm_start < start)
- vma_iter_config(vmi, vma->vm_start, start);
+ if (vma->vm_start < vmg->start)
+ vma_iter_config(vmg->vmi, vma->vm_start, vmg->start);
else
- vma_iter_config(vmi, end, vma->vm_end);
+ vma_iter_config(vmg->vmi, vmg->end, vma->vm_end);

- if (vma_iter_prealloc(vmi, NULL))
+ if (vma_iter_prealloc(vmg->vmi, NULL))
return -ENOMEM;

vma_start_write(vma);

init_vma_prep(&vp, vma);
vma_prepare(&vp);
- vma_adjust_trans_huge(vma, start, end, 0);
+ vma_adjust_trans_huge(vma, vmg->start, vmg->end, 0);

- vma_iter_clear(vmi);
- vma_set_range(vma, start, end, pgoff);
- vma_complete(&vp, vmi, vma->vm_mm);
+ vma_iter_clear(vmg->vmi);
+ vma_set_range(vma, vmg->start, vmg->end, vmg->pgoff);
+ vma_complete(&vp, vmg->vmi, vma->vm_mm);
return 0;
}

diff --git a/mm/vma.h b/mm/vma.h
index c31684cc1da6..c464d25da120 100644
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -66,12 +66,8 @@ void init_vma_prep(struct vma_prepare *vp,
void vma_complete(struct vma_prepare *vp,
struct vma_iterator *vmi, struct mm_struct *mm);

-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);
-
-int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
- unsigned long start, unsigned long end, pgoff_t pgoff);
+int vma_expand(struct vma_merge_struct *vmg);
+int vma_shrink(struct vma_merge_struct *vmg);

int
do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
diff --git a/tools/testing/vma/vma.c b/tools/testing/vma/vma.c
index 48e033c60d87..d216e51206c1 100644
--- a/tools/testing/vma/vma.c
+++ b/tools/testing/vma/vma.c
@@ -142,10 +142,17 @@ static bool test_simple_expand(void)
struct mm_struct mm = {};
struct vm_area_struct *vma = alloc_vma(&mm, 0, 0x1000, 0, flags);
VMA_ITERATOR(vmi, &mm, 0);
+ struct vma_merge_struct vmg = {
+ .vmi = &vmi,
+ .vma = vma,
+ .start = 0,
+ .end = 0x3000,
+ .pgoff = 0,
+ };

ASSERT_FALSE(vma_link(&mm, vma));

- ASSERT_FALSE(vma_expand(&vmi, vma, 0, 0x3000, 0, NULL));
+ ASSERT_FALSE(vma_expand(&vmg));

ASSERT_EQ(vma->vm_start, 0);
ASSERT_EQ(vma->vm_end, 0x3000);
@@ -163,10 +170,17 @@ static bool test_simple_shrink(void)
struct mm_struct mm = {};
struct vm_area_struct *vma = alloc_vma(&mm, 0, 0x3000, 0, flags);
VMA_ITERATOR(vmi, &mm, 0);
+ struct vma_merge_struct vmg = {
+ .vmi = &vmi,
+ .vma = vma,
+ .start = 0,
+ .end = 0x1000,
+ .pgoff = 0,
+ };

ASSERT_FALSE(vma_link(&mm, vma));

- ASSERT_FALSE(vma_shrink(&vmi, vma, 0, 0x1000, 0));
+ ASSERT_FALSE(vma_shrink(&vmg));

ASSERT_EQ(vma->vm_start, 0);
ASSERT_EQ(vma->vm_end, 0x1000);
--
2.45.2