[PATCH v5 2/7] dax: introduce dax device flag DAXDEV_RECOVERY

[Jane Chu]

Introduce dax device flag DAXDEV_RECOVERY to indicate a device
that is capable of recoverying from media poison.
For MD raid DAX devices, the capability is allowed for partial
device as oppose to the entire device. And the final poison
detection and repair rely on the provisioning base drivers.

Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
---
 drivers/dax/super.c   | 24 ++++++++++++++++++++++++
 drivers/nvdimm/pmem.c |  1 +
 include/linux/dax.h   | 14 ++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index e3029389d809..f4f607d9698b 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -109,6 +109,8 @@ enum dax_device_flags {
 	DAXDEV_NOCACHE,
 	/* handle CPU fetch exceptions during reads */
 	DAXDEV_NOMC,
+	/* flag to indicate device capable of poison recovery */
+	DAXDEV_RECOVERY,
 };
 
 /**
@@ -311,6 +313,28 @@ static void dax_destroy_inode(struct inode *inode)
 			"kill_dax() must be called before final iput()\n");
 }
 
+void set_dax_recovery(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_RECOVERY, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_recovery);
+
+bool dax_recovery_capable(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_RECOVERY, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_recovery_capable);
+
+int dax_prep_recovery(struct dax_device *dax_dev, void **kaddr)
+{
+	if (dax_recovery_capable(dax_dev)) {
+		set_bit(DAXDEV_RECOVERY, (unsigned long *)kaddr);
+		return 0;
+	}
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(dax_prep_recovery);
+
 static const struct super_operations dax_sops = {
 	.statfs = simple_statfs,
 	.alloc_inode = dax_alloc_inode,
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 58d95242a836..e8823813a8df 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -487,6 +487,7 @@ static int pmem_attach_disk(struct device *dev,
 	if (rc)
 		goto out_cleanup_dax;
 	dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
+	set_dax_recovery(dax_dev);
 	pmem->dax_dev = dax_dev;
 
 	rc = device_add_disk(dev, disk, pmem_attribute_groups);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 9fc5f99a0ae2..2fc776653c6e 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -40,6 +40,9 @@ void dax_write_cache(struct dax_device *dax_dev, bool wc);
 bool dax_write_cache_enabled(struct dax_device *dax_dev);
 bool dax_synchronous(struct dax_device *dax_dev);
 void set_dax_synchronous(struct dax_device *dax_dev);
+void set_dax_recovery(struct dax_device *dax_dev);
+bool dax_recovery_capable(struct dax_device *dax_dev);
+int dax_prep_recovery(struct dax_device *dax_dev, void **kaddr);
 /*
  * Check if given mapping is supported by the file / underlying device.
  */
@@ -87,6 +90,17 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
 {
 	return !(vma->vm_flags & VM_SYNC);
 }
+static inline void set_dax_recovery(struct dax_device *dax_dev)
+{
+}
+static inline bool dax_recovery_capable(struct dax_device *dax_dev)
+{
+	return false;
+}
+static inline int dax_prep_recovery(struct dax_device *dax_dev, void **kaddr)
+{
+	return -EINVAL;
+}
 #endif
 
 void set_dax_nocache(struct dax_device *dax_dev);
-- 
2.18.4