On 09/07/2012 11:19 AM, Alex Elder wrote:
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 <[email protected]>
---
Documentation/ABI/testing/sysfs-bus-rbd | 5 ++
drivers/block/rbd.c | 99
+++++++++++++++++++++++++++++++
2 files changed, 104 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-bus-rbd
b/Documentation/ABI/testing/sysfs-bus-rbd
index 3c17b62..7cbbe34 100644
--- a/Documentation/ABI/testing/sysfs-bus-rbd
+++ b/Documentation/ABI/testing/sysfs-bus-rbd
@@ -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.
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index ba68566..5a3132e 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -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,
@@ -2548,6 +2562,75 @@ out_err:
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;
+ ret = 0; /* rbd_req_sync_exec() can return positive */
The get_id class method will not return positive.
+
+ 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;
It would be clearer that this can't stay NULL if it were initialized
here instead of in the caller.
+ } else
+ dout("image_id is %s\n", rbd_dev->image_id);
If the first branch got braces, the second one should too.
+out:
+ kfree(response);
+ kfree(object_name);
+
+ return ret;
+}
+
static ssize_t rbd_add(struct bus_type *bus,
const char *buf,
size_t count)
@@ -2597,6 +2680,20 @@ 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 == -ENOENT) {
It's more than just -ENOENT. If the osd doesn't have a get_id method
for example, it will be -EINVAL. It's probably best to try format 1
if any error occurred, rather than trying to come up with an exhaustive
list that won't change in the future.
+ /* 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;
+ } else {
+ /* Not actually supporting format 2 yet */
+ goto err_out_client;
+ }
+
/* Create the name of the header object */
rbd_dev->header_name = kmalloc(rbd_dev->image_name_len
@@ -2688,6 +2785,7 @@ err_out_header:
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);
@@ -2744,6 +2842,7 @@ 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);
--
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