Re: [PATCH v5 9/9] cxl/pmem: Remove CXL SET_PARTITION_INFO from exclusive_cmds list

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Wed, 30 Mar 2022 18:27:19 -0700
alison.schofield@intel.com wrote:

> From: Alison Schofield <alison.schofield@intel.com>
> 
> With SET_PARTITION_INFO on the exclusive_cmds list for the CXL_PMEM
> driver, userspace cannot execute a set-partition command without
> first unbinding the pmem driver from the device.
> 
> When userspace requests a partition change to take effect on the
> next reboot this unbind requirement is unnecessarily restrictive.
> The driver does not need to enforce an unbind because partitions
> will not change until the next reboot. Of course, userspace still
> needs to be aware that changing the size of persistent capacity
> on the next reboot will result in the loss of data stored. That
> can happen regardless of whether it is presently bound at the time
> of issuing the set-partition command.
> 
> When userspace requests a partition change to take effect immediately,
> restrictions are needed. The CXL_MEM driver currently blocks the usage
> of immediate mode, making the presence of SET_PARTITION_INFO, in this
> exclusive commands list, redundant.
> 
> In the future, when the CXL_MEM driver adds support for immediate
> changes to device partitions it will ensure that the partition change
> will not affect any active decode. That means the work will not fall
> right back here, onto the CXL_PMEM driver.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
I gave a an RB on v3...  To make it easy for whoever
picks this up.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/cxl/pmem.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
> index 564d125d25ef..35c6f3af18f2 100644
> --- a/drivers/cxl/pmem.c
> +++ b/drivers/cxl/pmem.c
> @@ -344,7 +344,6 @@ static __init int cxl_pmem_init(void)
>  {
>  	int rc;
>  
> -	set_bit(CXL_MEM_COMMAND_ID_SET_PARTITION_INFO, exclusive_cmds);
>  	set_bit(CXL_MEM_COMMAND_ID_SET_SHUTDOWN_STATE, exclusive_cmds);
>  	set_bit(CXL_MEM_COMMAND_ID_SET_LSA, exclusive_cmds);
>