[PATCH v2 2/7] mm: Extend copy_vma()

Kirill Tkhai
2019-05-20T14:00:12Z

This prepares the function to copy a vma between
two processes. Two new arguments are introduced.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
include/linux/mm.h | 4 ++--
mm/mmap.c | 33 ++++++++++++++++++++++++---------
mm/mremap.c | 4 ++--
3 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0e8834ac32b7..afe07e4a76f8 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2329,8 +2329,8 @@ extern void __vma_link_rb(struct mm_struct *, struct vm_area_struct *,
struct rb_node **, struct rb_node *);
extern void unlink_file_vma(struct vm_area_struct *);
extern struct vm_area_struct *copy_vma(struct vm_area_struct **,
- unsigned long addr, unsigned long len, pgoff_t pgoff,
- bool *need_rmap_locks);
+ struct mm_struct *, unsigned long addr, unsigned long len,
+ pgoff_t pgoff, bool *need_rmap_locks, bool clear_flags_ctx);
extern void exit_mmap(struct mm_struct *);

static inline int check_data_rlimit(unsigned long rlim,
diff --git a/mm/mmap.c b/mm/mmap.c
index 57803a0a3a5c..99778e724ad1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3195,19 +3195,21 @@ int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
}

/*
- * Copy the vma structure to a new location in the same mm,
- * prior to moving page table entries, to effect an mremap move.
+ * Copy the vma structure to new location in the same vma
+ * prior to moving page table entries, to effect an mremap move;
*/
struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
- unsigned long addr, unsigned long len, pgoff_t pgoff,
- bool *need_rmap_locks)
+ struct mm_struct *mm, unsigned long addr,
+ unsigned long len, pgoff_t pgoff,
+ bool *need_rmap_locks, bool clear_flags_ctx)
{
struct vm_area_struct *vma = *vmap;
unsigned long vma_start = vma->vm_start;
- struct mm_struct *mm = vma->vm_mm;
+ struct vm_userfaultfd_ctx uctx;
struct vm_area_struct *new_vma, *prev;
struct rb_node **rb_link, *rb_parent;
bool faulted_in_anon_vma = true;
+ unsigned long flags;

/*
* If anonymous vma has not yet been faulted, update new pgoff
@@ -3220,15 +3222,25 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,

if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
return NULL; /* should never get here */
- new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
- vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
- vma->vm_userfaultfd_ctx);
+
+ uctx = vma->vm_userfaultfd_ctx;
+ flags = vma->vm_flags;
+ if (clear_flags_ctx) {
+ uctx = NULL_VM_UFFD_CTX;
+ flags &= ~(VM_UFFD_MISSING | VM_UFFD_WP | VM_MERGEABLE |
+ VM_LOCKED | VM_LOCKONFAULT | VM_WIPEONFORK |
+ VM_DONTCOPY);
+ }
+
+ new_vma = vma_merge(mm, prev, addr, addr + len, flags, vma->anon_vma,
+ vma->vm_file, pgoff, vma_policy(vma), uctx);
if (new_vma) {
/*
* Source vma may have been merged into new_vma
*/
if (unlikely(vma_start >= new_vma->vm_start &&
- vma_start < new_vma->vm_end)) {
+ vma_start < new_vma->vm_end) &&
+ vma->vm_mm == mm) {
/*
* The only way we can get a vma_merge with
* self during an mremap is if the vma hasn't
@@ -3249,6 +3261,9 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
new_vma = vm_area_dup(vma);
if (!new_vma)
goto out;
+ new_vma->vm_mm = mm;
+ new_vma->vm_flags = flags;
+ new_vma->vm_userfaultfd_ctx = uctx;
new_vma->vm_start = addr;
new_vma->vm_end = addr + len;
new_vma->vm_pgoff = pgoff;
diff --git a/mm/mremap.c b/mm/mremap.c
index 37b5b2ad91be..9a96cfc28675 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -352,8 +352,8 @@ static unsigned long move_vma(struct vm_area_struct *vma,
return err;

new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
- new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
- &need_rmap_locks);
+ new_vma = copy_vma(&vma, mm, new_addr, new_len, new_pgoff,
+ &need_rmap_locks, false);
if (!new_vma)
return -ENOMEM;