Re: [PATCH v4 11/11] md: fix abnormal io_opt from member disks

On Mon, Jan 12, 2026 at 12:30 PM Yu Kuai <[email protected]> wrote:
>
> It's reported that mtp3sas can report abnormal io_opt, for consequence,
> md array will end up with abnormal io_opt as well, due to the
> lcm_not_zero() from blk_stack_limits().
>
> Some personalities will configure optimal IO size, and it's indicate that
> users can get the best IO bandwidth if they issue IO with this size, and
> we don't want io_opt to be covered by member disks with abnormal io_opt.
>
> Fix this problem by adding a new mddev flags MD_STACK_IO_OPT to indicate
> that io_opt configured by personalities is preferred over member disks
> or not.

Hi Kuai

In v4, it doesn't use MD_STACK_IO_OPT anymore. So the comment needs to
be modified.

The patch looks good to me.

Reviewed-by: Xiao Ni <[email protected]>
>
> Reported-by: Filippo Giunchedi <[email protected]>
> Closes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1121006
> Reported-by: Coly Li <[email protected]>
> Closes: https://lore.kernel.org/all/[email protected]/
> Signed-off-by: Yu Kuai <[email protected]>
> ---
>  drivers/md/md.c     | 28 +++++++++++++++++++++++++++-
>  drivers/md/md.h     |  3 ++-
>  drivers/md/raid1.c  |  2 +-
>  drivers/md/raid10.c |  4 ++--
>  4 files changed, 32 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 731ec800f5cb..6c0fb09c26dc 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -6200,18 +6200,33 @@ static const struct kobj_type md_ktype = {
>
>  int mdp_major = 0;
>
> +static bool rdev_is_mddev(struct md_rdev *rdev)
> +{
> +       return rdev->bdev->bd_disk->fops == &md_fops;
> +}
> +
>  /* stack the limit for all rdevs into lim */
>  int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
>                 unsigned int flags)
>  {
>         struct md_rdev *rdev;
> +       bool io_opt_configured = lim->io_opt;
>
>         rdev_for_each(rdev, mddev) {
> +               unsigned int io_opt = lim->io_opt;
> +
>                 queue_limits_stack_bdev(lim, rdev->bdev, rdev->data_offset,
>                                         mddev->gendisk->disk_name);
>                 if ((flags & MDDEV_STACK_INTEGRITY) &&
>                     !queue_limits_stack_integrity_bdev(lim, rdev->bdev))
>                         return -EINVAL;
> +
> +               /*
> +                * If member disk is not mdraid array, keep the io_opt
> +                * from personality and ignore io_opt from member disk.
> +                */
> +               if (!rdev_is_mddev(rdev) && io_opt_configured)
> +                       lim->io_opt = io_opt;
>         }
>
>         /*
> @@ -6230,9 +6245,11 @@ int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
>  EXPORT_SYMBOL_GPL(mddev_stack_rdev_limits);
>
>  /* apply the extra stacking limits from a new rdev into mddev */
> -int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev)
> +int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev,
> +                        bool io_opt_configured)
>  {
>         struct queue_limits lim;
> +       unsigned int io_opt;
>
>         if (mddev_is_dm(mddev))
>                 return 0;
> @@ -6245,6 +6262,8 @@ int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev)
>         }
>
>         lim = queue_limits_start_update(mddev->gendisk->queue);
> +       io_opt = lim.io_opt;
> +
>         queue_limits_stack_bdev(&lim, rdev->bdev, rdev->data_offset,
>                                 mddev->gendisk->disk_name);
>
> @@ -6255,6 +6274,13 @@ int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev)
>                 return -ENXIO;
>         }
>
> +       /*
> +        * If member disk is not mdraid array, keep the io_opt from
> +        * personality and ignore io_opt from member disk.
> +        */
> +       if (!rdev_is_mddev(rdev) && io_opt_configured)
> +               lim.io_opt = io_opt;
> +
>         return queue_limits_commit_update(mddev->gendisk->queue, &lim);
>  }
>  EXPORT_SYMBOL_GPL(mddev_stack_new_rdev);
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index ddf989f2a139..80c527b3777d 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -1041,7 +1041,8 @@ int do_md_run(struct mddev *mddev);
>  #define MDDEV_STACK_INTEGRITY  (1u << 0)
>  int mddev_stack_rdev_limits(struct mddev *mddev, struct queue_limits *lim,
>                 unsigned int flags);
> -int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev);
> +int mddev_stack_new_rdev(struct mddev *mddev, struct md_rdev *rdev,
> +                        bool io_opt_configured);
>  void mddev_update_io_opt(struct mddev *mddev, unsigned int nr_stripes);
>
>  extern const struct block_device_operations md_fops;
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 1a957dba2640..f3f3086f27fa 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -1944,7 +1944,7 @@ static int raid1_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>         for (mirror = first; mirror <= last; mirror++) {
>                 p = conf->mirrors + mirror;
>                 if (!p->rdev) {
> -                       err = mddev_stack_new_rdev(mddev, rdev);
> +                       err = mddev_stack_new_rdev(mddev, rdev, false);
>                         if (err)
>                                 return err;
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 2c6b65b83724..a6edc91e7a9a 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -2139,7 +2139,7 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>                         continue;
>                 }
>
> -               err = mddev_stack_new_rdev(mddev, rdev);
> +               err = mddev_stack_new_rdev(mddev, rdev, true);
>                 if (err)
>                         return err;
>                 p->head_position = 0;
> @@ -2157,7 +2157,7 @@ static int raid10_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>                 clear_bit(In_sync, &rdev->flags);
>                 set_bit(Replacement, &rdev->flags);
>                 rdev->raid_disk = repl_slot;
> -               err = mddev_stack_new_rdev(mddev, rdev);
> +               err = mddev_stack_new_rdev(mddev, rdev, true);
>                 if (err)
>                         return err;
>                 conf->fullsync = 1;
> --
> 2.51.0
>
>