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Message-ID: <64f7a078298ec_1e8e7829471@iweiny-mobl.notmuch>
Date: Tue, 5 Sep 2023 14:41:12 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Ira Weiny <ira.weiny@...el.com>
CC: Dan Williams <dan.j.williams@...el.com>,
Navneet Singh <navneet.singh@...el.com>,
Fan Ni <fan.ni@...sung.com>,
Davidlohr Bueso <dave@...olabs.net>,
Dave Jiang <dave.jiang@...el.com>,
Alison Schofield <alison.schofield@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>,
<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 09/18] cxl/mem: Read extents on memory device
discovery
Jonathan Cameron wrote:
> On Mon, 28 Aug 2023 22:21:00 -0700
> Ira Weiny <ira.weiny@...el.com> wrote:
>
> > When a Dynamic Capacity Device (DCD) is realized some extents may
> > already be available within the DC Regions. This can happen if the host
> > has accepted extents and been rebooted or any other time the host driver
> > software has become out of sync with the device hardware.
> >
> > Read the available extents during probe and store them for later
> > use.
> >
> > Signed-off-by: Navneet Singh <navneet.singh@...el.com>
> > Co-developed-by: Navneet Singh <navneet.singh@...el.com>
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> >
> A few minor comments inline.
>
> Thanks,
>
> Jonathan
>
[snip]
>
> > +static int cxl_dev_get_dc_extent_cnt(struct cxl_memdev_state *mds,
> > + unsigned int *extent_gen_num)
> > +{
> > + struct cxl_mbox_get_dc_extent get_dc_extent;
> > + struct cxl_mbox_dc_extents dc_extents;
> > + struct device *dev = mds->cxlds.dev;
> > + struct cxl_mbox_cmd mbox_cmd;
> > + unsigned int count;
> > + int rc;
> > +
> > + /* Check GET_DC_EXTENT_LIST is supported by device */
> > + if (!test_bit(CXL_DCD_ENABLED_GET_EXTENT_LIST, mds->dcd_cmds)) {
> > + dev_dbg(dev, "unsupported cmd : get dyn cap extent list\n");
> > + return 0;
> > + }
> > +
> > + get_dc_extent = (struct cxl_mbox_get_dc_extent) {
> > + .extent_cnt = cpu_to_le32(0),
> > + .start_extent_index = cpu_to_le32(0),
> > + };
> > +
> > + mbox_cmd = (struct cxl_mbox_cmd) {
> > + .opcode = CXL_MBOX_OP_GET_DC_EXTENT_LIST,
> > + .payload_in = &get_dc_extent,
> > + .size_in = sizeof(get_dc_extent),
> > + .size_out = mds->payload_size,
>
> If all you are after is the count, then size_out can be a lot smaller than that
> I think as we know it can't return any extents.
Done.
>
> > + .payload_out = &dc_extents,
> > + .min_out = 1,
> > + };
> > +
> > + rc = cxl_internal_send_cmd(mds, &mbox_cmd);
> > + if (rc < 0)
> > + return rc;
> > +
> > + count = le32_to_cpu(dc_extents.total_extent_cnt);
> > + *extent_gen_num = le32_to_cpu(dc_extents.extent_list_num);
> > +
> > + return count;
> > +}
> > +
> > +static int cxl_dev_get_dc_extents(struct cxl_memdev_state *mds,
> > + unsigned int start_gen_num,
> > + unsigned int exp_cnt)
> > +{
> > + struct cxl_mbox_dc_extents *dc_extents;
> > + unsigned int start_index, total_read;
> > + struct device *dev = mds->cxlds.dev;
> > + struct cxl_mbox_cmd mbox_cmd;
> > + int retry = 3;
>
> Why 3?
Removed.
>
> > + int rc;
> > +
> > + /* Check GET_DC_EXTENT_LIST is supported by device */
> > + if (!test_bit(CXL_DCD_ENABLED_GET_EXTENT_LIST, mds->dcd_cmds)) {
> > + dev_dbg(dev, "unsupported cmd : get dyn cap extent list\n");
> > + return 0;
> > + }
> > +
> > + dc_extents = kvmalloc(mds->payload_size, GFP_KERNEL);
>
> Maybe __free magic would simplify this enough to be useful.
Yes. I'd not wrapped my head around the __free magic until you mentioned in
in the other patch. It is pretty easy to use. But I'm worried because it
seems 'too easy'... ;-)
I'll convert this one too. So far the other one seems good. So dare I
say "I know what I'm doing now"... :-D
>
> > + if (!dc_extents)
> > + return -ENOMEM;
> > +
> > +reset:
> > + total_read = 0;
> > + start_index = 0;
> > + do {
> > + unsigned int nr_ext, total_extent_cnt, gen_num;
> > + struct cxl_mbox_get_dc_extent get_dc_extent;
> > +
> > + get_dc_extent = (struct cxl_mbox_get_dc_extent) {
> > + .extent_cnt = exp_cnt - start_index,
> > + .start_extent_index = start_index,
> > + };
> > +
> > + mbox_cmd = (struct cxl_mbox_cmd) {
> > + .opcode = CXL_MBOX_OP_GET_DC_EXTENT_LIST,
> > + .payload_in = &get_dc_extent,
> > + .size_in = sizeof(get_dc_extent),
> > + .size_out = mds->payload_size,
> > + .payload_out = dc_extents,
> > + .min_out = 1,
> > + };
> > +
> > + rc = cxl_internal_send_cmd(mds, &mbox_cmd);
> > + if (rc < 0)
> > + goto out;
> > +
> > + nr_ext = le32_to_cpu(dc_extents->ret_extent_cnt);
> > + total_read += nr_ext;
> > + total_extent_cnt = le32_to_cpu(dc_extents->total_extent_cnt);
> > + gen_num = le32_to_cpu(dc_extents->extent_list_num);
> > +
> > + dev_dbg(dev, "Get extent list count:%d generation Num:%d\n",
> > + total_extent_cnt, gen_num);
> > +
> > + if (gen_num != start_gen_num || exp_cnt != total_extent_cnt) {
> > + dev_err(dev, "Extent list changed while reading; %u != %u : %u != %u\n",
> > + gen_num, start_gen_num, exp_cnt, total_extent_cnt);
> > + if (retry--)
> > + goto reset;
> > + return -EIO;
And this was a bug too :-( ... Fixed with the __free() magic.
Thanks for the review,
Ira
> > + }
> > +
> > + for (int i = 0; i < nr_ext ; i++) {
> > + dev_dbg(dev, "Storing extent %d/%d\n",
> > + start_index + i, exp_cnt);
> > + rc = cxl_store_dc_extent(mds, &dc_extents->extent[i]);
> > + if (rc)
> > + goto out;
> > + }
> > +
> > + start_index += nr_ext;
> > + } while (exp_cnt > total_read);
> > +
> > +out:
> > + kvfree(dc_extents);
> > + return rc;
> > +}
>
>
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