Re: [PATCH V6 09/10] cxl/mem: Retry reading CDAT on failure

Ben Widawsky
2022-02-01T18:59:34Z

On 22-01-31 23:19:51, ira.weiny@intel.com wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> The CDAT read may fail for a number of reasons but mainly it is possible
> to get different parts of a valid state. The checksum in the CDAT table
> protects against this.
>
> Now that the checksum is validated issue a retry if the CDAT read fails.
> For now 2 retries are implemented.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
>
> ---
> NOTE: Is 2 enough? Should this just be delayed until the time when the
> data is actually needed and not there?

I can't speak to retries at all, but one small issue below. It might make sense
if we keep this to make it a modparam.

>
> Changes from V5:
> New patch -- easy to push off or drop.
> ---
> drivers/cxl/core/memdev.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index a01068e98333..11d721c56f08 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -356,7 +356,8 @@ static const struct file_operations cxl_memdev_fops = {
> .llseek = noop_llseek,
> };
>
> -static int read_cdat_data(struct cxl_memdev *cxlmd, struct cxl_dev_state *cxlds)
> +static int __read_cdat_data(struct cxl_memdev *cxlmd,
> + struct cxl_dev_state *cxlds)
> {
> struct device *dev = &cxlmd->dev;
> size_t cdat_length;
> @@ -371,6 +372,20 @@ static int read_cdat_data(struct cxl_memdev *cxlmd, struct cxl_dev_state *cxlds)
> return cxl_mem_cdat_read_table(cxlds, &cxlmd->cdat);
> }
>
> +static int read_cdat_data(struct cxl_memdev *cxlmd,
> + struct cxl_dev_state *cxlds)
> +{
> + int retries = 2;
> + int rc;
> +
> + while (--retries) {

You either want retries--, or retries = 3...

> + rc = __read_cdat_data(cxlmd, cxlds);
> + if (!rc)
> + break;
> + }
> + return rc;
> +}
> +
> struct cxl_memdev *devm_cxl_add_memdev(struct cxl_dev_state *cxlds)
> {
> struct cxl_memdev *cxlmd;
> --
> 2.31.1
>