linux-kernel - Re: [PATCH v1 18/29] virtio-mem: factor out calculation of the bit number within the sb

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Date:   Tue, 20 Oct 2020 11:58:44 +0200
From:   Pankaj Gupta <pankaj.gupta.linux@...il.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, Linux MM <linux-mm@...ck.org>,
        virtualization@...ts.linux-foundation.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH v1 18/29] virtio-mem: factor out calculation of the bit
 number within the sb_states bitmap

> The calculation is already complicated enough, let's limit it to one
> location.
>
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Cc: Jason Wang <jasowang@...hat.com>
> Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  drivers/virtio/virtio_mem.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
> index 2cc497ad8298..73ff6e9ba839 100644
> --- a/drivers/virtio/virtio_mem.c
> +++ b/drivers/virtio/virtio_mem.c
> @@ -327,6 +327,16 @@ static int virtio_mem_sbm_mb_states_prepare_next_mb(struct virtio_mem *vm)
>              _mb_id--) \
>                 if (virtio_mem_sbm_get_mb_state(_vm, _mb_id) == _state)
>
> +/*
> + * Calculate the bit number in the sb_states bitmap for the given subblock
> + * inside the given memory block.
> + */
> +static int virtio_mem_sbm_sb_state_bit_nr(struct virtio_mem *vm,
> +                                         unsigned long mb_id, int sb_id)
> +{
> +       return (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> +}
> +
>  /*
>   * Mark all selected subblocks plugged.
>   *
> @@ -336,7 +346,7 @@ static void virtio_mem_sbm_set_sb_plugged(struct virtio_mem *vm,
>                                           unsigned long mb_id, int sb_id,
>                                           int count)
>  {
> -       const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> +       const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
>
>         __bitmap_set(vm->sbm.sb_states, bit, count);
>  }
> @@ -350,7 +360,7 @@ static void virtio_mem_sbm_set_sb_unplugged(struct virtio_mem *vm,
>                                             unsigned long mb_id, int sb_id,
>                                             int count)
>  {
> -       const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> +       const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
>
>         __bitmap_clear(vm->sbm.sb_states, bit, count);
>  }
> @@ -362,7 +372,7 @@ static bool virtio_mem_sbm_test_sb_plugged(struct virtio_mem *vm,
>                                            unsigned long mb_id, int sb_id,
>                                            int count)
>  {
> -       const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> +       const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
>
>         if (count == 1)
>                 return test_bit(bit, vm->sbm.sb_states);
> @@ -379,7 +389,7 @@ static bool virtio_mem_sbm_test_sb_unplugged(struct virtio_mem *vm,
>                                              unsigned long mb_id, int sb_id,
>                                              int count)
>  {
> -       const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> +       const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
>
>         /* TODO: Helper similar to bitmap_set() */
>         return find_next_bit(vm->sbm.sb_states, bit + count, bit) >=
> @@ -393,7 +403,7 @@ static bool virtio_mem_sbm_test_sb_unplugged(struct virtio_mem *vm,
>  static int virtio_mem_sbm_first_unplugged_sb(struct virtio_mem *vm,
>                                             unsigned long mb_id)
>  {
> -       const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb;
> +       const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, 0);
>
>         return find_next_zero_bit(vm->sbm.sb_states,
>                                   bit + vm->nb_sb_per_mb, bit) - bit;

Agree, there are alot of *b things, good to clean as much.

Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@...il.com>