[PATCH v7 45/70] userfaultfd: Use maple tree iterator to iterate VMAs

Liam Howlett
2022-04-04T14:40:22Z

Don't use the mm_struct linked list or the vma->vm_next in prep for removal

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
fs/userfaultfd.c | 49 ++++++++++++++++++++++-------------
include/linux/userfaultfd_k.h | 7 +++--
mm/mmap.c | 10 +++----
3 files changed, 39 insertions(+), 27 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index aa0c47cb0d16..f4bf95660536 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -610,14 +610,16 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
if (release_new_ctx) {
struct vm_area_struct *vma;
struct mm_struct *mm = release_new_ctx->mm;
+ VMA_ITERATOR(vmi, mm, 0);

/* the various vma->vm_userfaultfd_ctx still points to it */
mmap_write_lock(mm);
- for (vma = mm->mmap; vma; vma = vma->vm_next)
+ for_each_vma(vmi, vma) {
if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
vma->vm_flags &= ~__VM_UFFD_FLAGS;
}
+ }
mmap_write_unlock(mm);

userfaultfd_ctx_put(release_new_ctx);
@@ -798,11 +800,13 @@ static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
return false;
}

-int userfaultfd_unmap_prep(struct vm_area_struct *vma,
- unsigned long start, unsigned long end,
- struct list_head *unmaps)
+int userfaultfd_unmap_prep(struct mm_struct *mm, unsigned long start,
+ unsigned long end, struct list_head *unmaps)
{
- for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
+ VMA_ITERATOR(vmi, mm, start);
+ struct vm_area_struct *vma;
+
+ for_each_vma_range(vmi, vma, end) {
struct userfaultfd_unmap_ctx *unmap_ctx;
struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;

@@ -852,6 +856,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
/* len == 0 means wake all */
struct userfaultfd_wake_range range = { .len = 0, };
unsigned long new_flags;
+ MA_STATE(mas, &mm->mm_mt, 0, 0);

WRITE_ONCE(ctx->released, true);

@@ -868,7 +873,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
*/
mmap_write_lock(mm);
prev = NULL;
- for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ mas_for_each(&mas, vma, ULONG_MAX) {
cond_resched();
BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
!!(vma->vm_flags & __VM_UFFD_FLAGS));
@@ -1285,6 +1290,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
bool found;
bool basic_ioctls;
unsigned long start, end, vma_end;
+ MA_STATE(mas, &mm->mm_mt, 0, 0);

user_uffdio_register = (struct uffdio_register __user *) arg;

@@ -1327,7 +1333,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
goto out;

mmap_write_lock(mm);
- vma = find_vma_prev(mm, start, &prev);
+ mas_set(&mas, start);
+ vma = mas_find(&mas, ULONG_MAX);
if (!vma)
goto out_unlock;

@@ -1352,7 +1359,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
*/
found = false;
basic_ioctls = false;
- for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
+ for (cur = vma; cur; cur = mas_next(&mas, end - 1)) {
cond_resched();

BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
@@ -1412,8 +1419,10 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
}
BUG_ON(!found);

- if (vma->vm_start < start)
- prev = vma;
+ mas_set(&mas, start);
+ prev = mas_prev(&mas, 0);
+ if (prev != vma)
+ mas_next(&mas, ULONG_MAX);

ret = 0;
do {
@@ -1471,8 +1480,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
skip:
prev = vma;
start = vma->vm_end;
- vma = vma->vm_next;
- } while (vma && vma->vm_start < end);
+ vma = mas_next(&mas, end - 1);
+ } while (vma);
out_unlock:
mmap_write_unlock(mm);
mmput(mm);
@@ -1516,6 +1525,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
bool found;
unsigned long start, end, vma_end;
const void __user *buf = (void __user *)arg;
+ MA_STATE(mas, &mm->mm_mt, 0, 0);

ret = -EFAULT;
if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
@@ -1534,7 +1544,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
goto out;

mmap_write_lock(mm);
- vma = find_vma_prev(mm, start, &prev);
+ mas_set(&mas, start);
+ vma = mas_find(&mas, ULONG_MAX);
if (!vma)
goto out_unlock;

@@ -1559,7 +1570,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
*/
found = false;
ret = -EINVAL;
- for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
+ for (cur = vma; cur; cur = mas_next(&mas, end - 1)) {
cond_resched();

BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
@@ -1579,8 +1590,10 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
}
BUG_ON(!found);

- if (vma->vm_start < start)
- prev = vma;
+ mas_set(&mas, start);
+ prev = mas_prev(&mas, 0);
+ if (prev != vma)
+ mas_next(&mas, ULONG_MAX);

ret = 0;
do {
@@ -1645,8 +1658,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
skip:
prev = vma;
start = vma->vm_end;
- vma = vma->vm_next;
- } while (vma && vma->vm_start < end);
+ vma = mas_next(&mas, end - 1);
+ } while (vma);
out_unlock:
mmap_write_unlock(mm);
mmput(mm);
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 33cea484d1ad..e0b2ec2c20f2 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -139,9 +139,8 @@ extern bool userfaultfd_remove(struct vm_area_struct *vma,
unsigned long start,
unsigned long end);

-extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
- unsigned long start, unsigned long end,
- struct list_head *uf);
+extern int userfaultfd_unmap_prep(struct mm_struct *mm, unsigned long start,
+ unsigned long end, struct list_head *uf);
extern void userfaultfd_unmap_complete(struct mm_struct *mm,
struct list_head *uf);

@@ -222,7 +221,7 @@ static inline bool userfaultfd_remove(struct vm_area_struct *vma,
return true;
}

-static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
+static inline int userfaultfd_unmap_prep(struct mm_struct *mm,
unsigned long start, unsigned long end,
struct list_head *uf)
{
diff --git a/mm/mmap.c b/mm/mmap.c
index 0c548c7bbfe7..d648b551893e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2499,7 +2499,7 @@ do_mas_align_munmap(struct ma_state *mas, struct vm_area_struct *vma,
* split, despite we could. This is unlikely enough
* failure that it's not worth optimizing it for.
*/
- int error = userfaultfd_unmap_prep(vma, start, end, uf);
+ int error = userfaultfd_unmap_prep(mm, start, end, uf);

if (error)
return error;
@@ -2984,10 +2984,7 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
goto munmap_full_vma;
}

- vma_init(&unmap, mm);
- unmap.vm_start = newbrk;
- unmap.vm_end = oldbrk;
- ret = userfaultfd_unmap_prep(&unmap, newbrk, oldbrk, uf);
+ ret = userfaultfd_unmap_prep(mm, newbrk, oldbrk, uf);
if (ret)
return ret;
ret = 1;
@@ -3000,6 +2997,9 @@ static int do_brk_munmap(struct ma_state *mas, struct vm_area_struct *vma,
}

vma->vm_end = newbrk;
+ vma_init(&unmap, mm);
+ unmap.vm_start = newbrk;
+ unmap.vm_end = oldbrk;
if (vma_mas_remove(&unmap, mas))
goto mas_store_fail;

--
2.34.1