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

[Jane Chu]

On 7/30/2021 3:01 AM, Shiyang Ruan wrote:
> This is the case where the holder represents a mapped device, or a list
> of mapped devices more exactly(because it is possible to create more
> than one mapped device on one pmem device).

Could you share how do you test this scenario?

thanks,
-jane

> 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 <ruansy.fnst@xxxxxxxxxxx>
> ---
>   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
>    */