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* [PATCH] libnvdimm, pfn: during init, clear errors in the metadata area
@ 2018-09-18 20:07 Vishal Verma
  2018-09-18 20:53 ` Dan Williams
  0 siblings, 1 reply; 3+ messages in thread
From: Vishal Verma @ 2018-09-18 20:07 UTC (permalink / raw)
  To: linux-nvdimm

If there are badblocks present in the 'struct page' area for pfn
namespaces, until now, the only way to clear them has been to force the
namespace into raw mode, clear the errors, and re-enable the fsdax mode.
This is clunky, given that it should be easy enough for the pfn driver
to do the same.

Add a new helper that uses the most recently available badblocks list to
check whether there are any badblocks that lie in the volatile struct
page area. If so, before initializing the struct pages, send down
targeted writes via nvdimm_write_bytes to write zeroes to the affected
blocks, and thus clear errors.

Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 drivers/nvdimm/pfn_devs.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/drivers/nvdimm/pfn_devs.c b/drivers/nvdimm/pfn_devs.c
index 3f7ad5bc443e..04b341758cd6 100644
--- a/drivers/nvdimm/pfn_devs.c
+++ b/drivers/nvdimm/pfn_devs.c
@@ -361,8 +361,59 @@ struct device *nd_pfn_create(struct nd_region *nd_region)
 	return dev;
 }
 
+static int nd_pfn_clear_meta_errors(struct nd_pfn *nd_pfn)
+{
+	struct nd_region *nd_region = to_nd_region(nd_pfn->dev.parent);
+	struct nd_namespace_common *ndns = nd_pfn->ndns;
+	void *zero_page = page_address(ZERO_PAGE(0));
+	struct nd_pfn_sb *pfn_sb = nd_pfn->pfn_sb;
+	sector_t first_bad, meta_start;
+	struct nd_namespace_io *nsio;
+	int num_bad, meta_num, rc;
+	bool bb_present;
+
+	nsio = to_nd_namespace_io(&ndns->dev);
+	meta_start = (SZ_4K + sizeof(*pfn_sb)) >> 9;
+	meta_num = (le64_to_cpu(pfn_sb->dataoff) >> 9) - meta_start;
+
+	do {
+		unsigned long zero_len;
+		u64 nsoff;
+
+		bb_present = !!badblocks_check(&nd_region->bb, meta_start,
+				meta_num, &first_bad, &num_bad);
+		if (bb_present) {
+			dev_dbg(&nd_pfn->dev, "meta: %x badblocks at %lx\n",
+					num_bad, first_bad);
+			nsoff = (nd_region->ndr_start + (first_bad << 9)) -
+					nsio->res.start;
+			zero_len = num_bad << 9;
+			while (zero_len) {
+				unsigned long chunk = min(zero_len, PAGE_SIZE);
+
+				rc = nvdimm_write_bytes(ndns, nsoff, zero_page,
+							chunk, 0);
+				if (rc)
+					break;
+
+				zero_len -= chunk;
+				nsoff += chunk;
+			}
+			if (rc) {
+				dev_err(&nd_pfn->dev,
+					"error clearing %x badblocks at %lx\n",
+					num_bad, first_bad);
+				return rc;
+			}
+		}
+	} while (bb_present);
+
+	return 0;
+}
+
 int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 {
+	int rc;
 	u64 checksum, offset;
 	enum nd_pfn_mode mode;
 	struct nd_namespace_io *nsio;
@@ -477,6 +528,12 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 		return -ENXIO;
 	}
 
+	if (mode == PFN_MODE_PMEM) {
+		rc = nd_pfn_clear_meta_errors(nd_pfn);
+		if (rc)
+			return rc;
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(nd_pfn_validate);
-- 
2.14.4

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2018-09-18 20:07 [PATCH] libnvdimm, pfn: during init, clear errors in the metadata area Vishal Verma
2018-09-18 20:53 ` Dan Williams
2018-09-18 22:21   ` Verma, Vishal L

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