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    Subject[PATCH v7 45/70] userfaultfd: Use maple tree iterator to iterate VMAs
    Date
    From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>

    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
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