linux-kernel - Re: [PATCH 14/23] md/dm-raid: remove max_write

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Message-ID: <CALTww296VZXQoBryTLkYj+JkXtQoNOuzG2SwHbnTk1KxSGRjKw@mail.gmail.com>
Date: Wed, 28 May 2025 12:58:05 +0800
From: Xiao Ni <xni@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: hch@....de, colyli@...nel.org, song@...nel.org, yukuai3@...wei.com, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-raid@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com, 
	johnny.chenyi@...wei.com
Subject: Re: [PATCH 14/23] md/dm-raid: remove max_write_behind setting limit

On Sat, May 24, 2025 at 2:18 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> The comments said 'vaule in kB', while the value actually means the
> number of write_behind IOs. And since md-bitmap will automatically
> adjust the value to max COUNTER_MAX / 2, there is no need to fail
> early.
>
> Also move some macros that is only used md-bitmap.c.
>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>  drivers/md/dm-raid.c   |  6 +-----
>  drivers/md/md-bitmap.c | 10 ++++++++++
>  drivers/md/md-bitmap.h |  9 ---------
>  3 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index 088cfe6e0f98..9757c32ea1f5 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -1356,11 +1356,7 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
>                                 return -EINVAL;
>                         }
>
> -                       /*
> -                        * In device-mapper, we specify things in sectors, but
> -                        * MD records this value in kB
> -                        */
> -                       if (value < 0 || value / 2 > COUNTER_MAX) {
> +                       if (value < 0) {
>                                 rs->ti->error = "Max write-behind limit out of range";
>                                 return -EINVAL;
>                         }
> diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
> index 535bc1888e8c..098e7b6cd187 100644
> --- a/drivers/md/md-bitmap.c
> +++ b/drivers/md/md-bitmap.c
> @@ -98,9 +98,19 @@
>   *
>   */
>
> +typedef __u16 bitmap_counter_t;
> +
>  #define PAGE_BITS (PAGE_SIZE << 3)
>  #define PAGE_BIT_SHIFT (PAGE_SHIFT + 3)
>
> +#define COUNTER_BITS 16
> +#define COUNTER_BIT_SHIFT 4
> +#define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
> +
> +#define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
> +#define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
> +#define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
> +
>  #define NEEDED(x) (((bitmap_counter_t) x) & NEEDED_MASK)
>  #define RESYNC(x) (((bitmap_counter_t) x) & RESYNC_MASK)
>  #define COUNTER(x) (((bitmap_counter_t) x) & COUNTER_MAX)
> diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h
> index d2cdf831ef1a..a9a0f6a8d96d 100644
> --- a/drivers/md/md-bitmap.h
> +++ b/drivers/md/md-bitmap.h
> @@ -9,15 +9,6 @@
>
>  #define BITMAP_MAGIC 0x6d746962
>
> -typedef __u16 bitmap_counter_t;
> -#define COUNTER_BITS 16
> -#define COUNTER_BIT_SHIFT 4
> -#define COUNTER_BYTE_SHIFT (COUNTER_BIT_SHIFT - 3)
> -
> -#define NEEDED_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 1)))
> -#define RESYNC_MASK ((bitmap_counter_t) (1 << (COUNTER_BITS - 2)))
> -#define COUNTER_MAX ((bitmap_counter_t) RESYNC_MASK - 1)
> -
>  /*
>   * version 3 is host-endian order, this is deprecated and not used for new
>   * array
> --
> 2.39.2
>

Reviewed-by: Xiao Ni <xni@...hat.com>