[PATCH v5 5/7] pmem: add pmem_recovery_write() dax op

Jane Chu
2022-01-28T21:32:48Z

pmem_recovery_write() consists of clearing poison via DSM,
clearing page HWPoison bit, re-state _PAGE_PRESENT bit,
cacheflush, write, and finally clearing bad-block record.

A competing pread thread is held off during recovery write
by the presence of bad-block record. A competing recovery_write
thread is serialized by a lock.

Signed-off-by: Jane Chu <jane.chu@oracle.com>
---
drivers/nvdimm/pmem.c | 82 +++++++++++++++++++++++++++++++++++++++----
drivers/nvdimm/pmem.h | 1 +
2 files changed, 77 insertions(+), 6 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 638e64681db9..f2d6b34d48de 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -69,6 +69,14 @@ static void hwpoison_clear(struct pmem_device *pmem,
}
}

+static void pmem_clear_badblocks(struct pmem_device *pmem, sector_t sector,
+ long cleared_blks)
+{
+ badblocks_clear(&pmem->bb, sector, cleared_blks);
+ if (pmem->bb_state)
+ sysfs_notify_dirent(pmem->bb_state);
+}
+
static blk_status_t pmem_clear_poison(struct pmem_device *pmem,
phys_addr_t offset, unsigned int len)
{
@@ -88,9 +96,7 @@ static blk_status_t pmem_clear_poison(struct pmem_device *pmem,
dev_dbg(dev, "%#llx clear %ld sector%s\n",
(unsigned long long) sector, cleared,
cleared > 1 ? "s" : "");
- badblocks_clear(&pmem->bb, sector, cleared);
- if (pmem->bb_state)
- sysfs_notify_dirent(pmem->bb_state);
+ pmem_clear_badblocks(pmem, sector, cleared);
}

arch_invalidate_pmem(pmem->virt_addr + offset, len);
@@ -257,10 +263,15 @@ static int pmem_rw_page(struct block_device *bdev, sector_t sector,
__weak long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
long nr_pages, void **kaddr, pfn_t *pfn)
{
+ bool bad_pmem;
+ bool do_recovery = false;
resource_size_t offset = PFN_PHYS(pgoff) + pmem->data_offset;

- if (unlikely(is_bad_pmem(&pmem->bb, PFN_PHYS(pgoff) / 512,
- PFN_PHYS(nr_pages))))
+ bad_pmem = is_bad_pmem(&pmem->bb, PFN_PHYS(pgoff) / 512,
+ PFN_PHYS(nr_pages));
+ if (bad_pmem && kaddr)
+ do_recovery = dax_recovery_started(pmem->dax_dev, kaddr);
+ if (bad_pmem && !do_recovery)
return -EIO;

if (kaddr)
@@ -301,10 +312,68 @@ static long pmem_dax_direct_access(struct dax_device *dax_dev,
return __pmem_direct_access(pmem, pgoff, nr_pages, kaddr, pfn);
}

+/*
+ * The recovery write thread started out as a normal pwrite thread and
+ * when the filesystem was told about potential media error in the
+ * range, filesystem turns the normal pwrite to a dax_recovery_write.
+ *
+ * The recovery write consists of clearing poison via DSM, clearing page
+ * HWPoison bit, reenable page-wide read-write permission, flush the
+ * caches and finally write. A competing pread thread needs to be held
+ * off during the recovery process since data read back might not be valid.
+ * And that's achieved by placing the badblock records clearing after
+ * the completion of the recovery write.
+ *
+ * Any competing recovery write thread needs to be serialized, and this is
+ * done via pmem device level lock .recovery_lock.
+ */
static size_t pmem_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
void *addr, size_t bytes, struct iov_iter *i)
{
- return 0;
+ size_t rc, len, off;
+ phys_addr_t pmem_off;
+ struct pmem_device *pmem = dax_get_private(dax_dev);
+ struct device *dev = pmem->bb.dev;
+ sector_t sector;
+ long cleared, cleared_blk;
+
+ mutex_lock(&pmem->recovery_lock);
+
+ /* If no poison found in the range, go ahead with write */
+ off = (unsigned long)addr & ~PAGE_MASK;
+ len = PFN_PHYS(PFN_UP(off + bytes));
+ if (!is_bad_pmem(&pmem->bb, PFN_PHYS(pgoff) / 512, len)) {
+ rc = _copy_from_iter_flushcache(addr, bytes, i);
+ goto write_done;
+ }
+
+ /* Not page-aligned range cannot be recovered */
+ if (off || !(PAGE_ALIGNED(bytes))) {
+ dev_warn(dev, "Found poison, but addr(%p) or bytes(%#lx) not page aligned\n",
+ addr, bytes);
+ rc = (size_t) -EIO;
+ goto write_done;
+ }
+
+ pmem_off = PFN_PHYS(pgoff) + pmem->data_offset;
+ sector = (pmem_off - pmem->data_offset) / 512;
+ cleared = nvdimm_clear_poison(dev, pmem->phys_addr + pmem_off, len);
+ cleared_blk = cleared / 512;
+ if (cleared_blk > 0) {
+ hwpoison_clear(pmem, pmem->phys_addr + pmem_off, cleared);
+ } else {
+ dev_warn(dev, "pmem_recovery_write: cleared_blk: %ld\n",
+ cleared_blk);
+ rc = (size_t) -EIO;
+ goto write_done;
+ }
+ arch_invalidate_pmem(pmem->virt_addr + pmem_off, bytes);
+ rc = _copy_from_iter_flushcache(addr, bytes, i);
+ pmem_clear_badblocks(pmem, sector, cleared_blk);
+
+write_done:
+ mutex_unlock(&pmem->recovery_lock);
+ return rc;
}

static const struct dax_operations pmem_dax_ops = {
@@ -495,6 +564,7 @@ static int pmem_attach_disk(struct device *dev,
goto out_cleanup_dax;
dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
set_dax_recovery(dax_dev);
+ mutex_init(&pmem->recovery_lock);
pmem->dax_dev = dax_dev;

rc = device_add_disk(dev, disk, pmem_attribute_groups);
diff --git a/drivers/nvdimm/pmem.h b/drivers/nvdimm/pmem.h
index 59cfe13ea8a8..971bff7552d6 100644
--- a/drivers/nvdimm/pmem.h
+++ b/drivers/nvdimm/pmem.h
@@ -24,6 +24,7 @@ struct pmem_device {
struct dax_device *dax_dev;
struct gendisk *disk;
struct dev_pagemap pgmap;
+ struct mutex recovery_lock;
};

long __pmem_direct_access(struct pmem_device *pmem, pgoff_t pgoff,
--
2.18.4