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rbd: get parent spec for version 2 images

Add support for getting the the information identifying the parent
image for rbd images that have them.  The child image holds a
reference to its parent image specification structure.  Create a new
entry "parent" in /sys/bus/rbd/image/N/ to report the identifying
information for the parent image, if any.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
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1 parent a92ffdf commit 86b00e0da6be7bbc16412f126c5b548ac5d91d50 Alex Elder committed Oct 26, 2012
Showing with 137 additions and 0 deletions.
  1. +4 −0 Documentation/ABI/testing/sysfs-bus-rbd
  2. +131 −0 drivers/block/rbd.c
  3. +2 −0 include/linux/ceph/rados.h
View
4 Documentation/ABI/testing/sysfs-bus-rbd
@@ -70,6 +70,10 @@ snap_*
A directory per each snapshot
+parent
+
+ Information identifying the pool, image, and snapshot id for
+ the parent image in a layered rbd image (format 2 only).
Entries under /sys/bus/rbd/devices/<dev-id>/snap_<snap-name>
-------------------------------------------------------------
View
131 drivers/block/rbd.c
@@ -217,6 +217,9 @@ struct rbd_device {
struct ceph_osd_event *watch_event;
struct ceph_osd_request *watch_request;
+ struct rbd_spec *parent_spec;
+ u64 parent_overlap;
+
/* protects updating the header */
struct rw_semaphore header_rwsem;
@@ -2009,6 +2012,49 @@ static ssize_t rbd_snap_show(struct device *dev,
return sprintf(buf, "%s\n", rbd_dev->spec->snap_name);
}
+/*
+ * For an rbd v2 image, shows the pool id, image id, and snapshot id
+ * for the parent image. If there is no parent, simply shows
+ * "(no parent image)".
+ */
+static ssize_t rbd_parent_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
+ struct rbd_spec *spec = rbd_dev->parent_spec;
+ int count;
+ char *bufp = buf;
+
+ if (!spec)
+ return sprintf(buf, "(no parent image)\n");
+
+ count = sprintf(bufp, "pool_id %llu\npool_name %s\n",
+ (unsigned long long) spec->pool_id, spec->pool_name);
+ if (count < 0)
+ return count;
+ bufp += count;
+
+ count = sprintf(bufp, "image_id %s\nimage_name %s\n", spec->image_id,
+ spec->image_name ? spec->image_name : "(unknown)");
+ if (count < 0)
+ return count;
+ bufp += count;
+
+ count = sprintf(bufp, "snap_id %llu\nsnap_name %s\n",
+ (unsigned long long) spec->snap_id, spec->snap_name);
+ if (count < 0)
+ return count;
+ bufp += count;
+
+ count = sprintf(bufp, "overlap %llu\n", rbd_dev->parent_overlap);
+ if (count < 0)
+ return count;
+ bufp += count;
+
+ return (ssize_t) (bufp - buf);
+}
+
static ssize_t rbd_image_refresh(struct device *dev,
struct device_attribute *attr,
const char *buf,
@@ -2032,6 +2078,7 @@ 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(parent, S_IRUGO, rbd_parent_show, NULL);
static struct attribute *rbd_attrs[] = {
&dev_attr_size.attr,
@@ -2043,6 +2090,7 @@ static struct attribute *rbd_attrs[] = {
&dev_attr_name.attr,
&dev_attr_image_id.attr,
&dev_attr_current_snap.attr,
+ &dev_attr_parent.attr,
&dev_attr_refresh.attr,
NULL
};
@@ -2192,6 +2240,7 @@ struct rbd_device *rbd_dev_create(struct rbd_client *rbdc,
static void rbd_dev_destroy(struct rbd_device *rbd_dev)
{
+ rbd_spec_put(rbd_dev->parent_spec);
kfree(rbd_dev->header_name);
rbd_put_client(rbd_dev->rbd_client);
rbd_spec_put(rbd_dev->spec);
@@ -2400,6 +2449,71 @@ static int rbd_dev_v2_features(struct rbd_device *rbd_dev)
&rbd_dev->header.features);
}
+static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
+{
+ struct rbd_spec *parent_spec;
+ size_t size;
+ void *reply_buf = NULL;
+ __le64 snapid;
+ void *p;
+ void *end;
+ char *image_id;
+ u64 overlap;
+ size_t len = 0;
+ int ret;
+
+ parent_spec = rbd_spec_alloc();
+ if (!parent_spec)
+ return -ENOMEM;
+
+ size = sizeof (__le64) + /* pool_id */
+ sizeof (__le32) + RBD_IMAGE_ID_LEN_MAX + /* image_id */
+ sizeof (__le64) + /* snap_id */
+ sizeof (__le64); /* overlap */
+ reply_buf = kmalloc(size, GFP_KERNEL);
+ if (!reply_buf) {
+ ret = -ENOMEM;
+ goto out_err;
+ }
+
+ snapid = cpu_to_le64(CEPH_NOSNAP);
+ ret = rbd_req_sync_exec(rbd_dev, rbd_dev->header_name,
+ "rbd", "get_parent",
+ (char *) &snapid, sizeof (snapid),
+ (char *) reply_buf, size,
+ CEPH_OSD_FLAG_READ, NULL);
+ dout("%s: rbd_req_sync_exec returned %d\n", __func__, ret);
+ if (ret < 0)
+ goto out_err;
+
+ ret = -ERANGE;
+ p = reply_buf;
+ end = (char *) reply_buf + size;
+ ceph_decode_64_safe(&p, end, parent_spec->pool_id, out_err);
+ if (parent_spec->pool_id == CEPH_NOPOOL)
+ goto out; /* No parent? No problem. */
+
+ image_id = ceph_extract_encoded_string(&p, end, &len, GFP_KERNEL);
+ if (IS_ERR(image_id)) {
+ ret = PTR_ERR(image_id);
+ goto out_err;
+ }
+ parent_spec->image_id = image_id;
+ ceph_decode_64_safe(&p, end, parent_spec->snap_id, out_err);
+ ceph_decode_64_safe(&p, end, overlap, out_err);
+
+ rbd_dev->parent_overlap = overlap;
+ rbd_dev->parent_spec = parent_spec;
+ parent_spec = NULL; /* rbd_dev now owns this */
+out:
+ ret = 0;
+out_err:
+ kfree(reply_buf);
+ rbd_spec_put(parent_spec);
+
+ return ret;
+}
+
static int rbd_dev_v2_snap_context(struct rbd_device *rbd_dev, u64 *ver)
{
size_t size;
@@ -3154,6 +3268,12 @@ static int rbd_dev_v1_probe(struct rbd_device *rbd_dev)
ret = rbd_read_header(rbd_dev, &rbd_dev->header);
if (ret < 0)
goto out_err;
+
+ /* Version 1 images have no parent (no layering) */
+
+ rbd_dev->parent_spec = NULL;
+ rbd_dev->parent_overlap = 0;
+
rbd_dev->image_format = 1;
dout("discovered version 1 image, header name is %s\n",
@@ -3205,6 +3325,14 @@ static int rbd_dev_v2_probe(struct rbd_device *rbd_dev)
if (ret < 0)
goto out_err;
+ /* If the image supports layering, get the parent info */
+
+ if (rbd_dev->header.features & RBD_FEATURE_LAYERING) {
+ ret = rbd_dev_v2_parent_info(rbd_dev);
+ if (ret < 0)
+ goto out_err;
+ }
+
/* crypto and compression type aren't (yet) supported for v2 images */
rbd_dev->header.crypt_type = 0;
@@ -3224,6 +3352,9 @@ static int rbd_dev_v2_probe(struct rbd_device *rbd_dev)
return 0;
out_err:
+ rbd_dev->parent_overlap = 0;
+ rbd_spec_put(rbd_dev->parent_spec);
+ rbd_dev->parent_spec = NULL;
kfree(rbd_dev->header_name);
rbd_dev->header_name = NULL;
kfree(rbd_dev->header.object_prefix);
View
2 include/linux/ceph/rados.h
@@ -87,6 +87,8 @@ struct ceph_pg {
*
* lpgp_num -- as above.
*/
+#define CEPH_NOPOOL ((__u64) (-1)) /* pool id not defined */
+
#define CEPH_PG_TYPE_REP 1
#define CEPH_PG_TYPE_RAID4 2
#define CEPH_PG_POOL_VERSION 2

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