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

Ira Weiny
2022-02-01T22:32:02Z

On Tue, Feb 01, 2022 at 10:59:28AM -0800, Widawsky, Ben wrote:
> 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.

Not a bad idea.

>
> >
> > 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...

Opps yea.

Thanks,
Ira

>
> > + 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
> >