fs/userfaultfd: Stop using vma linked list.

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>

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 003f0d31743eb3cd95de8c8da21a4d0d731daf73..bd181f922999416d2a26edce8ff3765c8bfc8af7 100644 (file)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -606,14 +606,18 @@ 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;
+               MA_STATE(mas, &mm->mm_mt, 0, 0);
 
                /* the various vma->vm_userfaultfd_ctx still points to it */
                mmap_write_lock(mm);
-               for (vma = mm->mmap; vma; vma = vma->vm_next)
+               mas_lock(&mas);
+               mas_for_each(&mas, vma, ULONG_MAX) {
                        if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
                                vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
                                vma->vm_flags &= ~__VM_UFFD_FLAGS;
                        }
+               }
+               mas_unlock(&mas);
                mmap_write_unlock(mm);
 
                userfaultfd_ctx_put(release_new_ctx);
@@ -798,7 +802,10 @@ int userfaultfd_unmap_prep(struct vm_area_struct *vma,
                           unsigned long start, unsigned long end,
                           struct list_head *unmaps)
 {
-       for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
+       MA_STATE(mas, &vma->vm_mm->mm_mt, vma->vm_start, vma->vm_start);
+
+       rcu_read_lock();
+       mas_for_each(&mas, vma, end) {
                struct userfaultfd_unmap_ctx *unmap_ctx;
                struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
 
@@ -817,6 +824,7 @@ int userfaultfd_unmap_prep(struct vm_area_struct *vma,
                unmap_ctx->end = end;
                list_add_tail(&unmap_ctx->list, unmaps);
        }
+       rcu_read_unlock();
 
        return 0;
 }
@@ -848,6 +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);
 
@@ -863,9 +872,11 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
         * taking the mmap_lock for writing.
         */
        mmap_write_lock(mm);
+       mas_lock(&mas);
        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));
                if (vma->vm_userfaultfd_ctx.ctx != ctx) {
@@ -885,6 +896,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
                vma->vm_flags = new_flags;
                vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
        }
+       mas_unlock(&mas);
        mmap_write_unlock(mm);
        mmput(mm);
 wakeup:
@@ -1281,6 +1293,7 @@ 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;
 
@@ -1323,6 +1336,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
                goto out;
 
        mmap_write_lock(mm);
+       mas_lock(&mas);
        vma = find_vma_prev(mm, start, &prev);
        if (!vma)
                goto out_unlock;
@@ -1348,7 +1362,8 @@ 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) {
+       mas_set(&mas, vma->vm_start);
+       mas_for_each(&mas, cur, end) {
                cond_resched();
 
                BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
@@ -1466,9 +1481,10 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
        skip:
                prev = vma;
                start = vma->vm_end;
-               vma = vma->vm_next;
+               vma = vma_next(mm, vma);
        } while (vma && vma->vm_start < end);
 out_unlock:
+       mas_unlock(&mas);
        mmap_write_unlock(mm);
        mmput(mm);
        if (!ret) {
@@ -1511,6 +1527,7 @@ 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)))
@@ -1529,6 +1546,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
                goto out;
 
        mmap_write_lock(mm);
+       mas_lock(&mas);
        vma = find_vma_prev(mm, start, &prev);
        if (!vma)
                goto out_unlock;
@@ -1554,7 +1572,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
         */
        found = false;
        ret = -EINVAL;
-       for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
+       mas_set(&mas, vma->vm_start);
+       mas_for_each(&mas, cur, end) {
                cond_resched();
 
                BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
@@ -1640,9 +1659,10 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
        skip:
                prev = vma;
                start = vma->vm_end;
-               vma = vma->vm_next;
+               vma = vma_next(mm, vma);
        } while (vma && vma->vm_start < end);
 out_unlock:
+       mas_unlock(&mas);
        mmap_write_unlock(mm);
        mmput(mm);
 out: