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rbd: define rbd_dev_image_id()

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New format 2 rbd images are permanently identified by a unique image
id.  Each rbd image also has a name, but the name can be changed.
A format 2 rbd image will have an object--whose name is based on the
image name--which maps an image's name to its image id.

Create a new function rbd_dev_image_id() that checks for the
existence of the image id object, and if it's found, records the
image id in the rbd_device structure.

Create a new rbd device attribute (/sys/bus/rbd/<num>/image_id) that
makes this information available.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
This commit is contained in:
Alex Elder 2012-07-10 20:30:11 -05:00
parent 3bb59ad515
commit 589d30e0b3
2 changed files with 105 additions and 0 deletions
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5
Documentation/ABI/testing/sysfs-bus-rbd
View file

@ -33,6 +33,11 @@ name
The name of the rbd image.
image_id
The unique id for the rbd image. (For rbd image format 1
this is empty.)
pool
The name of the storage pool where this rbd image resides.

100
drivers/block/rbd.c
View file

@ -66,6 +66,8 @@
#define RBD_SNAP_HEAD_NAME "-"
#define RBD_IMAGE_ID_LEN_MAX 64
/*
* An RBD device name will be "rbd#", where the "rbd" comes from
* RBD_DRV_NAME above, and # is a unique integer identifier.
@ -173,6 +175,8 @@ struct rbd_device {
spinlock_t lock; /* queue lock */
struct rbd_image_header header;
char *image_id;
size_t image_id_len;
char *image_name;
size_t image_name_len;
char *header_name;
@ -1987,6 +1991,14 @@ static ssize_t rbd_name_show(struct device *dev,
return sprintf(buf, "%s\n", rbd_dev->image_name);
}
static ssize_t rbd_image_id_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
return sprintf(buf, "%s\n", rbd_dev->image_id);
}
static ssize_t rbd_snap_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@ -2015,6 +2027,7 @@ static DEVICE_ATTR(client_id, S_IRUGO, rbd_client_id_show, NULL);
static DEVICE_ATTR(pool, S_IRUGO, rbd_pool_show, NULL);
static DEVICE_ATTR(pool_id, S_IRUGO, rbd_pool_id_show, NULL);
static DEVICE_ATTR(name, S_IRUGO, rbd_name_show, NULL);
static DEVICE_ATTR(image_id, S_IRUGO, rbd_image_id_show, NULL);
static DEVICE_ATTR(refresh, S_IWUSR, NULL, rbd_image_refresh);
static DEVICE_ATTR(current_snap, S_IRUGO, rbd_snap_show, NULL);
static DEVICE_ATTR(create_snap, S_IWUSR, NULL, rbd_snap_add);
@ -2026,6 +2039,7 @@ static struct attribute *rbd_attrs[] = {
&dev_attr_pool.attr,
&dev_attr_pool_id.attr,
&dev_attr_name.attr,
&dev_attr_image_id.attr,
&dev_attr_current_snap.attr,
&dev_attr_refresh.attr,
&dev_attr_create_snap.attr,
@ -2553,6 +2567,75 @@ dout(" SNAP_NAME is <%s>, len is %zd\n", snap_name, len);
return err_ptr;
}
/*
* An rbd format 2 image has a unique identifier, distinct from the
* name given to it by the user. Internally, that identifier is
* what's used to specify the names of objects related to the image.
*
* A special "rbd id" object is used to map an rbd image name to its
* id. If that object doesn't exist, then there is no v2 rbd image
* with the supplied name.
*
* This function will record the given rbd_dev's image_id field if
* it can be determined, and in that case will return 0. If any
* errors occur a negative errno will be returned and the rbd_dev's
* image_id field will be unchanged (and should be NULL).
*/
static int rbd_dev_image_id(struct rbd_device *rbd_dev)
{
int ret;
size_t size;
char *object_name;
void *response;
void *p;
/*
* First, see if the format 2 image id file exists, and if
* so, get the image's persistent id from it.
*/
size = sizeof (RBD_ID_PREFIX) + rbd_dev->image_name_len;
object_name = kmalloc(size, GFP_NOIO);
if (!object_name)
return -ENOMEM;
sprintf(object_name, "%s%s", RBD_ID_PREFIX, rbd_dev->image_name);
dout("rbd id object name is %s\n", object_name);
/* Response will be an encoded string, which includes a length */
size = sizeof (__le32) + RBD_IMAGE_ID_LEN_MAX;
response = kzalloc(size, GFP_NOIO);
if (!response) {
ret = -ENOMEM;
goto out;
}
ret = rbd_req_sync_exec(rbd_dev, object_name,
"rbd", "get_id",
NULL, 0,
response, RBD_IMAGE_ID_LEN_MAX,
CEPH_OSD_FLAG_READ, NULL);
dout("%s: rbd_req_sync_exec returned %d\n", __func__, ret);
if (ret < 0)
goto out;
p = response;
rbd_dev->image_id = ceph_extract_encoded_string(&p,
p + RBD_IMAGE_ID_LEN_MAX,
&rbd_dev->image_id_len,
GFP_NOIO);
if (IS_ERR(rbd_dev->image_id)) {
ret = PTR_ERR(rbd_dev->image_id);
rbd_dev->image_id = NULL;
} else {
dout("image_id is %s\n", rbd_dev->image_id);
}
out:
kfree(response);
kfree(object_name);
return ret;
}
static ssize_t rbd_add(struct bus_type *bus,
const char *buf,
size_t count)
@ -2600,6 +2683,21 @@ 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
@ -2691,6 +2789,7 @@ static ssize_t rbd_add(struct bus_type *bus,
err_out_client:
kfree(rbd_dev->header_name);
rbd_put_client(rbd_dev);
kfree(rbd_dev->image_id);
err_out_args:
kfree(rbd_dev->mapping.snap_name);
kfree(rbd_dev->image_name);
@ -2746,6 +2845,7 @@ static void rbd_dev_release(struct device *dev)
/* done with the id, and with the rbd_dev */
kfree(rbd_dev->mapping.snap_name);
kfree(rbd_dev->image_id);
kfree(rbd_dev->header_name);
kfree(rbd_dev->pool_name);
kfree(rbd_dev->image_name);