Re: [PATCH RESEND v6 8/9] md: Implement dax_holder_operations

Find out which mapped device the offset belongs to, and translate the
offset from target device to mapped device.  When it is done, call
dax_corrupted_range() for the holder of this mapped device.

Signed-off-by: Shiyang Ruan <redacted>
---
  drivers/md/dm.c | 126 +++++++++++++++++++++++++++++++++++++++++++++++-
  1 file changed, 125 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 2c5f9e585211..a35b9a97a73f 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c

@@ -626,7 +626,11 @@ static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU)
  }
  
  static char *_dm_claim_ptr = "I belong to device-mapper";
-
+static const struct dax_holder_operations dm_dax_holder_ops;
+struct dm_holder {
+	struct list_head list;
+	struct mapped_device *md;
+};
  /*
   * Open a table device so we can use it as a map destination.
   */

@@ -634,6 +638,8 @@ static int open_table_device(struct table_device *td, dev_t dev,
  			     struct mapped_device *md)
  {
  	struct block_device *bdev;
+	struct list_head *holders;
+	struct dm_holder *holder;
  
  	int r;
  

@@ -651,6 +657,19 @@ static int open_table_device(struct table_device *td, dev_t dev,
  
  	td->dm_dev.bdev = bdev;
  	td->dm_dev.dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
+	if (!td->dm_dev.dax_dev)
+		return 0;
+
+	holders = dax_get_holder(td->dm_dev.dax_dev);
+	if (!holders) {
+		holders = kmalloc(sizeof(*holders), GFP_KERNEL);
+		INIT_LIST_HEAD(holders);
+		dax_set_holder(td->dm_dev.dax_dev, holders, &dm_dax_holder_ops);
+	}
+	holder = kmalloc(sizeof(*holder), GFP_KERNEL);
+	holder->md = md;
+	list_add_tail(&holder->list, holders);
+
  	return 0;
  }
  

@@ -659,9 +678,27 @@ static int open_table_device(struct table_device *td, dev_t dev,
   */
  static void close_table_device(struct table_device *td, struct mapped_device *md)
  {
+	struct list_head *holders;
+	struct dm_holder *holder, *n;
+
  	if (!td->dm_dev.bdev)
  		return;
  
+	holders = dax_get_holder(td->dm_dev.dax_dev);
+	if (holders) {
+		list_for_each_entry_safe(holder, n, holders, list) {
+			if (holder->md == md) {
+				list_del(&holder->list);
+				kfree(holder);
+			}
+		}
+		if (list_empty(holders)) {
+			kfree(holders);
+			/* unset dax_device's holder_data */
+			dax_set_holder(td->dm_dev.dax_dev, NULL, NULL);
+		}
+	}
+
  	bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md));
  	blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL);
  	put_dax(td->dm_dev.dax_dev);

@@ -1115,6 +1152,89 @@ static int dm_dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
  	return ret;
  }
  
+#if IS_ENABLED(CONFIG_DAX_DRIVER)
+struct corrupted_hit_info {
+	struct dax_device *dax_dev;
+	sector_t offset;
+};
+
+static int dm_blk_corrupted_hit(struct dm_target *ti, struct dm_dev *dev,
+				sector_t start, sector_t count, void *data)
+{
+	struct corrupted_hit_info *bc = data;
+
+	return bc->dax_dev == (void *)dev->dax_dev &&
+			(start <= bc->offset && bc->offset < start + count);
+}
+
+struct corrupted_do_info {
+	size_t length;
+	void *data;
+};
+
+static int dm_blk_corrupted_do(struct dm_target *ti, struct block_device *bdev,
+			       sector_t sector, void *data)
+{
+	struct mapped_device *md = ti->table->md;
+	struct corrupted_do_info *bc = data;
+
+	return dax_holder_notify_failure(md->dax_dev, to_bytes(sector),
+					 bc->length, bc->data);
+}
+
+static int dm_dax_notify_failure_one(struct mapped_device *md,
+				     struct dax_device *dax_dev,
+				     loff_t offset, size_t length, void *data)
+{
+	struct dm_table *map;
+	struct dm_target *ti;
+	sector_t sect = to_sector(offset);
+	struct corrupted_hit_info hi = {dax_dev, sect};
+	struct corrupted_do_info di = {length, data};
+	int srcu_idx, i, rc = -ENODEV;
+
+	map = dm_get_live_table(md, &srcu_idx);
+	if (!map)
+		return rc;
+
+	/*
+	 * find the target device, and then translate the offset of this target
+	 * to the whole mapped device.
+	 */
+	for (i = 0; i < dm_table_get_num_targets(map); i++) {
+		ti = dm_table_get_target(map, i);
+		if (!(ti->type->iterate_devices && ti->type->rmap))
+			continue;
+		if (!ti->type->iterate_devices(ti, dm_blk_corrupted_hit, &hi))
+			continue;
+
+		rc = ti->type->rmap(ti, sect, dm_blk_corrupted_do, &di);
+		break;
+	}
+
+	dm_put_live_table(md, srcu_idx);
+	return rc;
+}
+
+static int dm_dax_notify_failure(struct dax_device *dax_dev,
+				 loff_t offset, size_t length, void *data)
+{
+	struct dm_holder *holder;
+	struct list_head *holders = dax_get_holder(dax_dev);
+	int rc = -ENODEV;
+
+	list_for_each_entry(holder, holders, list) {
+		rc = dm_dax_notify_failure_one(holder->md, dax_dev, offset,
+					       length, data);
+		if (rc != -ENODEV)
+			break;
+	}
+	return rc;
+}
+#else
+#define dm_dax_notify_failure NULL
+#endif
+
  /*
   * A target may call dm_accept_partial_bio only from the map routine.  It is
   * allowed for all bio types except REQ_PREFLUSH, REQ_OP_ZONE_* zone management

@@ -3057,6 +3177,10 @@ static const struct dax_operations dm_dax_ops = {
  	.zero_page_range = dm_dax_zero_page_range,
  };
  
+static const struct dax_holder_operations dm_dax_holder_ops = {
+	.notify_failure = dm_dax_notify_failure,
+};
+
  /*
   * module hooks
   */