On Mon, Dec 23, 2019 at 1:49 AM <jgq516@xxxxxxxxx> wrote:
>
> From: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
>
> So far, IO serialization is used for two scenarios:
>
> 1. raid1 which enables write-behind mode, and there is rdev in the array
> which is multi-queue device and flaged with writemostly.
> 2. IO serialization is enabled or disabled by change serialize_policy.
>
> So introduce rdev_need_serial to check the first scenario. And for 1, IO
> serialization is enabled automatically while 2 is controlled manually.
>
> And it is possible that both scenarios are true, so for create serial pool,
> rdev/rdevs_init_serial should be separate from check if the pool existed or
> not. Then for destroy pool, we need to check if the pool is needed by other
> rdevs due to the first scenario.
>
> Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxxxxxxxx>
> ---
> drivers/md/md.c | 71 +++++++++++++++++++++++++++++--------------------
> 1 file changed, 42 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 796cf70e1c9f..788559f42d43 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -147,28 +147,40 @@ static void rdevs_init_serial(struct mddev *mddev)
> }
>
> /*
> - * Create serial_info_pool for raid1 under conditions:
> - * 1. rdev is the first multi-queue device flaged with writemostly,
> - * also write-behind mode is enabled.
> - * 2. rdev is NULL, means want to enable serialization for all rdevs.
> + * rdev needs to enable serial stuffs if it meets the conditions:
> + * 1. it is multi-queue device flaged with writemostly.
> + * 2. the write-behind mode is enabled.
> + */
> +static int rdev_need_serial(struct md_rdev *rdev)
> +{
> + return (rdev && rdev->mddev->bitmap_info.max_write_behind > 0 &&
I guess there is not need to check rdev here?
Thanks,
Song
