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

[ruansy.fnst@xxxxxxxxxxx]

> -----Original Message-----
> From: Jane Chu <jane.chu@xxxxxxxxxx>
> Subject: Re: [PATCH RESEND v6 8/9] md: Implement dax_holder_operations
> 
> 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?

Do you mean "more than one mapped device on one pmem device"?

1. Create 2 partitions on a pmem device(fsdax mode).
2. Create LVM(one LV) on each partition.
3. Create xfs filesystem on each LVM.
4. Memory failure on this pmem.

In this case, there are 2 LVMs on one pmem device.  So we should register this 2 LVMs in dax_holder, and iterate them when notifying the failure.

--
Thanks,
Ruan.

> 
> 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
> >    */
> >