On Thursday, November 03, 2016 3:34 AM Andrea Arcangeli wrote:
> +void madvise_userfault_dontneed(struct vm_area_struct *vma,
> + struct vm_area_struct **prev,
> + unsigned long start, unsigned long end)
> +{
> + struct userfaultfd_ctx *ctx;
> + struct userfaultfd_wait_queue ewq;
> +
> + ctx = vma->vm_userfaultfd_ctx.ctx;
> + if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_MADVDONTNEED))
> + return;
> +
> + userfaultfd_ctx_get(ctx);
> + *prev = NULL; /* We wait for ACK w/o the mmap semaphore */
> + up_read(&vma->vm_mm->mmap_sem);
> +
> + msg_init(&ewq.msg);
> +
> + ewq.msg.event = UFFD_EVENT_MADVDONTNEED;
> + ewq.msg.arg.madv_dn.start = start;
> + ewq.msg.arg.madv_dn.end = end;
> +
> + userfaultfd_event_wait_completion(ctx, &ewq);
> +
> + down_read(&vma->vm_mm->mmap_sem);
After napping with mmap_sem released, is vma still valid?
> +}
> +
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