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    Subject[PATCH v4 16/33] mm/mmap: write-lock VMAs in vma_prepare before modifying them
    From
    Write-lock all VMAs which might be affected by a merge, split, expand
    or shrink operations. All these operations use vma_prepare() before
    making the modifications, therefore it provides a centralized place to
    perform VMA locking.

    Signed-off-by: Suren Baghdasaryan <surenb@google.com>
    ---
    mm/mmap.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    diff --git a/mm/mmap.c b/mm/mmap.c
    index 92893d86c0af..e73fbb84ce12 100644
    --- a/mm/mmap.c
    +++ b/mm/mmap.c
    @@ -502,6 +502,16 @@ static inline void init_vma_prep(struct vma_prepare *vp,
    */
    static inline void vma_prepare(struct vma_prepare *vp)
    {
    + if (vp->vma)
    + vma_start_write(vp->vma);
    + if (vp->adj_next)
    + vma_start_write(vp->adj_next);
    + /* vp->insert is always a newly created VMA, no need for locking */
    + if (vp->remove)
    + vma_start_write(vp->remove);
    + if (vp->remove2)
    + vma_start_write(vp->remove2);
    +
    if (vp->file) {
    uprobe_munmap(vp->vma, vp->vma->vm_start, vp->vma->vm_end);

    --
    2.39.2.722.g9855ee24e9-goog
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