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Commit a30b71b9 authored by Alex Elder's avatar Alex Elder
Browse files

rbd: lay out header probe infrastructure 



This defines a new function rbd_dev_probe() as a top-level
function for populating detailed information about an rbd device.

It first checks for the existence of a format 2 rbd image id object.
If it exists, the image is assumed to be a format 2 rbd image, and
another function rbd_dev_v2() is called to finish populating
header data for that image.  If it does not exist, it is assumed to
be an old (format 1) rbd image, and calls a similar function
rbd_dev_v1() to populate its header information.

A new field, rbd_dev->format, is defined to record which version
of the rbd image format the device represents.  For a valid mapped
rbd device it will have one of two values, 1 or 2.

So far, the format 2 images are not really supported; this is
laying out the infrastructure for fleshing out that support.

Signed-off-by: default avatarAlex Elder <elder@inktank.com>
Reviewed-by: default avatarJosh Durgin <josh.durgin@inktank.com>
parent cd892126

drivers/block/rbd.c

+99 −28
Original line number Diff line number Diff line
@@ -170,6 +170,7 @@ struct rbd_device { 
	int			major;		/* blkdev assigned major */

	struct gendisk		*disk;		/* blkdev's gendisk and rq */



	u32			image_format;	/* Either 1 or 2 */

	struct rbd_options	rbd_opts;

	struct rbd_client	*rbd_client;
@@ -507,6 +508,11 @@ static void rbd_coll_release(struct kref *kref) 
	kfree(coll);

}



static bool rbd_image_format_valid(u32 image_format)

{

	return image_format == 1 || image_format == 2;

}



static bool rbd_dev_ondisk_valid(struct rbd_image_header_ondisk *ondisk)

{

	size_t size;
@@ -2584,6 +2590,96 @@ static int rbd_dev_image_id(struct rbd_device *rbd_dev) 
	return ret;

}



static int rbd_dev_v1_probe(struct rbd_device *rbd_dev)

{

	int ret;

	size_t size;



	/* Version 1 images have no id; empty string is used */



	rbd_dev->image_id = kstrdup("", GFP_KERNEL);

	if (!rbd_dev->image_id)

		return -ENOMEM;

	rbd_dev->image_id_len = 0;



	/* Record the header object name for this rbd image. */



	size = rbd_dev->image_name_len + sizeof (RBD_SUFFIX);

	rbd_dev->header_name = kmalloc(size, GFP_KERNEL);

	if (!rbd_dev->header_name) {

		ret = -ENOMEM;

		goto out_err;

	}

	sprintf(rbd_dev->header_name, "%s%s", rbd_dev->image_name, RBD_SUFFIX);



	/* Populate rbd image metadata */



	ret = rbd_read_header(rbd_dev, &rbd_dev->header);

	if (ret < 0)

		goto out_err;

	rbd_dev->image_format = 1;



	dout("discovered version 1 image, header name is %s\n",

		rbd_dev->header_name);



	return 0;



out_err:

	kfree(rbd_dev->header_name);

	rbd_dev->header_name = NULL;

	kfree(rbd_dev->image_id);

	rbd_dev->image_id = NULL;



	return ret;

}



static int rbd_dev_v2_probe(struct rbd_device *rbd_dev)

{

	size_t size;



	/*

	 * Image id was filled in by the caller.  Record the header

	 * object name for this rbd image.

	 */

	size = sizeof (RBD_HEADER_PREFIX) + rbd_dev->image_id_len;

	rbd_dev->header_name = kmalloc(size, GFP_KERNEL);

	if (!rbd_dev->header_name)

		return -ENOMEM;

	sprintf(rbd_dev->header_name, "%s%s",

			RBD_HEADER_PREFIX, rbd_dev->image_id);

	rbd_dev->image_format = 2;



	dout("discovered version 2 image, header name is %s\n",

		rbd_dev->header_name);



	return -ENOTSUPP;

}



/*

 * Probe for the existence of the header object for the given rbd

 * device.  For format 2 images this includes determining the image

 * id.

 */

static int rbd_dev_probe(struct rbd_device *rbd_dev)

{

	int ret;



	/*

	 * Get the id from the image id object.  If it's not a

	 * format 2 image, we'll get ENOENT back, and we'll assume

	 * it's a format 1 image.

	 */

	ret = rbd_dev_image_id(rbd_dev);

	if (ret)

		ret = rbd_dev_v1_probe(rbd_dev);

	else

		ret = rbd_dev_v2_probe(rbd_dev);

	if (ret)

		dout("probe failed, returning %d\n", ret);



	return ret;

}



static ssize_t rbd_add(struct bus_type *bus,

		       const char *buf,

		       size_t count)
@@ -2631,35 +2727,10 @@ static ssize_t rbd_add(struct bus_type *bus, 
		goto err_out_client;

	rbd_dev->pool_id = rc;



	rc = rbd_dev_image_id(rbd_dev);

	if (!rc) {

		rc = -ENOTSUPP;	/* Not actually supporting format 2 yet */

		goto err_out_client;

	}



	/* Version 1 images have no id; empty string is used */



	rbd_dev->image_id = kstrdup("", GFP_KERNEL);

	if (!rbd_dev->image_id) {

		rc = -ENOMEM;

		goto err_out_client;

	}

	rbd_dev->image_id_len = 0;



	/* Create the name of the header object */



	rbd_dev->header_name = kmalloc(rbd_dev->image_name_len

						+ sizeof (RBD_SUFFIX),

					GFP_KERNEL);

	if (!rbd_dev->header_name)

		goto err_out_client;

	sprintf(rbd_dev->header_name, "%s%s", rbd_dev->image_name, RBD_SUFFIX);



	/* Get information about the image being mapped */



	rc = rbd_read_header(rbd_dev, &rbd_dev->header);

	if (rc)

	rc = rbd_dev_probe(rbd_dev);

	if (rc < 0)

		goto err_out_client;

	rbd_assert(rbd_image_format_valid(rbd_dev->image_format));



	/* no need to lock here, as rbd_dev is not registered yet */

	rc = rbd_dev_snaps_update(rbd_dev);