On Thu, 25 Feb 2016 22:02:40 +0800 Minfei Huang <mhuang at redhat.com> wrote:
> From: Minfei Huang <mnfhuang at gmail.com>
>
> For some arch, kexec shall map the reserved pages, then use them, when
> we try to start the kdump service.
>
> kexec may return directly, without unmaping the reserved pages, if it
> fails during starting service. To fix it, we make a pair of map/unmap
> reserved pages both in generic path and error path.
This patch both refactors the code AND fixes the bug. It is a
decent-looking refactoring, but mixing the two together makes it *much*
harder to review the bugfix. These two steps should be separated
please, with the bugfix patch coming first.
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -103,6 +103,68 @@ out_free_image:
> return ret;
> }
>
> +static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
> + struct kexec_segment __user *segments, unsigned long flags)
> +{
> + struct kimage **dest_image, *image;
> + unsigned long i;
> + int ret;
> +
> + if (flags & KEXEC_ON_CRASH)
> + dest_image = &kexec_crash_image;
> + else
> + dest_image = &kexec_image;
> +
> + if (nr_segments == 0) {
> + /* Uninstall image */
> + kimage_free(xchg(dest_image, NULL));
> + return 0;
> + }
> + if (flags & KEXEC_ON_CRASH) {
> + /*
> + * Loading another kernel to switch to if this one
> + * crashes. Free any current crash dump kernel before
> + * we corrupt it.
> + */
> + kimage_free(xchg(&kexec_crash_image, NULL));
> + }
> +
> + ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
> + if (ret)
> + return ret;
This is a bug, isn't it? Missed kimage_free().
> + if (flags & KEXEC_ON_CRASH)
> + crash_map_reserved_pages();
> +
> + if (flags & KEXEC_PRESERVE_CONTEXT)
> + image->preserve_context = 1;
> +
> + ret = machine_kexec_prepare(image);
> + if (ret)
> + goto out;
> +
> + for (i = 0; i < nr_segments; i++) {
> + ret = kimage_load_segment(image, &image->segment[i]);
> + if (ret)
> + goto out;
> + }
> +
> + kimage_terminate(image);
> +
> + /* Install the new kernel and uninstall the old */
> + image = xchg(dest_image, image);
> +
> +out:
> + /*
> + * Once the reserved memory is mapped, we should unmap this memory
> + * before returning
> + */
> + if (flags & KEXEC_ON_CRASH)
> + crash_unmap_reserved_pages();
> + kimage_free(image);
> + return ret;
> +}
> +
>
> ...
>
