linux-kernel - Re: [dm-devel] [PATCH 2/2] dm: Add support for data integrity to DM

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Message-Id: <20080923.152942.41629825.k-ueda@ct.jp.nec.com>
Date:	Tue, 23 Sep 2008 15:29:42 -0400 (EDT)
From:	Kiyoshi Ueda <k-ueda@...jp.nec.com>
To:	martin.petersen@...cle.com
Cc:	agk@...rceware.org, jens.axboe@...cle.com,
	linux-kernel@...r.kernel.org, dm-devel@...hat.com,
	k-ueda@...jp.nec.com
Subject: Re: [dm-devel] [PATCH 2/2] dm: Add support for data integrity to DM

Hi Martin,

On Tue, 23 Sep 2008 14:41:12 -0400, "Martin K. Petersen" wrote:
> If all subdevices support the same protection format the DM device is
> flagged as capable.
> 
> Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
> ---
>  drivers/md/dm-table.c         |   35 ++++++++++++++++++++++++++++++++++-
>  drivers/md/dm.c               |   24 ++++++++++++++++++++++--
>  drivers/md/dm.h               |    2 +-
>  include/linux/device-mapper.h |    1 +
>  4 files changed, 58 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> index 61f4414..7290a90 100644
> --- a/drivers/md/dm-table.c
> +++ b/drivers/md/dm-table.c
> @@ -841,8 +841,12 @@ struct dm_target *dm_table_find_target(struct dm_table *t, sector_t sector)
>  	return &t->targets[(KEYS_PER_NODE * n) + k];
>  }
>  
> -void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
> +void dm_table_set_restrictions(struct dm_table *t, struct mapped_device *md)
>  {
> +	struct request_queue *q = dm_queue(md);
> +	struct list_head *devices = dm_table_get_devices(t);
> +	struct dm_dev *prev, *cur;
> +
>  	/*
>  	 * Make sure we obey the optimistic sub devices
>  	 * restrictions.
> @@ -861,6 +865,35 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q)
>  	else
>  		queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, q);
>  
> +	/*
> +	 * Run through all devices to ensure they have matching
> +	 * integrity profile
> +	 */
> +	cur = prev = NULL;
> +
> +	list_for_each_entry(cur, devices, list) {
> +
> +		if (prev && blk_integrity_compare(prev->bdev, cur->bdev) < 0) {
> +			printk(KERN_ERR "%s: %s %s Integrity mismatch!\n",
> +			       __func__, prev->bdev->bd_disk->disk_name,
> +			       cur->bdev->bd_disk->disk_name);
> +			return;
> +		}
> +		prev = cur;
> +	}
> +
> +	/* Register dm device as being integrity capable */
> +	if (prev && bdev_get_integrity(prev->bdev)) {
> +		struct gendisk *disk = dm_disk(md);
> +
> +		if (blk_integrity_register(dm_disk(md),
> +					   bdev_get_integrity(prev->bdev)))
> +			printk(KERN_ERR "%s: %s Could not register integrity!\n",
> +			       __func__, disk->disk_name);
> +		else
> +			printk(KERN_INFO "Enabling data integrity on %s\n",
> +			       disk->disk_name);
> +	}
>  }
<snip>
> @@ -1200,7 +1216,6 @@ static void __set_size(struct mapped_device *md, sector_t size)
>  
>  static int __bind(struct mapped_device *md, struct dm_table *t)
>  {
> -	struct request_queue *q = md->queue;
>  	sector_t size;
>  
>  	size = dm_table_get_size(t);
> @@ -1221,7 +1236,7 @@ static int __bind(struct mapped_device *md, struct dm_table *t)
>  
>  	write_lock(&md->map_lock);
>  	md->map = t;
> -	dm_table_set_restrictions(t, q);
> +	dm_table_set_restrictions(t, md);
>  	write_unlock(&md->map_lock);
>  
>  	return 0;

Creating another function (e.g. dm_table_set_integrity(t, md)) may
be better, since then you wouldn't need dm_queue() nor need to change
the function interface of dm_table_set_restrictions() I think.


> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index a90222e..5cf3a89 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -200,6 +200,7 @@ void dm_uevent_add(struct mapped_device *md, struct list_head *elist);
>  const char *dm_device_name(struct mapped_device *md);
>  int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid);
>  struct gendisk *dm_disk(struct mapped_device *md);
> +struct request_queue *dm_queue(struct mapped_device *md);
>  int dm_suspended(struct mapped_device *md);
>  int dm_noflush_suspending(struct dm_target *ti);

If you need dm_queue() anyway, this part should be in drivers/md/dm.h
because other kernel modules like dm target drivers (e.g. dm-mirror)
don't use it.

Thanks,
Kiyoshi Ueda
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