[PATCH 08/16] rbd: don't store pool name in struct rbd_dev

[Alex Elder <elder@inktank.com>]

An rbd device's pool name is used to specify the pool to use for an
rbd image when it gets mapped (via rbd_add()).  However, only the
pool id can be relied on to be invariant--the name of a pool can
change at any time.

This means that the name of the pool is potentially stale as soon as
the image is mapped, so it's a bad idea to record this information.
So only store the pool id, not its name, in an rbd_dev.

Here are a few specific notes about this change:
    - The "pool" name device attribute (/sys/bus/rbd/devices/<N>/pool)
      goes away.  In its place is a "pool_id" attribute that provide
      the numeric pool id for the rbd image.
    - rbd_add_parse_args() now returns a pointer to a dynamically-
      allocated copy of the pool name taken from the arguments.
    - rbd_add() has been changed to handle freeing the pool name,
      both in error cases and in the normal case after the pool id
      has been recorded.

Signed-off-by: Alex Elder <elder@inktank.com>
---
 drivers/block/rbd.c |   74
+++++++++++++++++++++++++++++++-------------------
 1 files changed, 46 insertions(+), 28 deletions(-)

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 3aa0ca0..76e978c 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -56,7 +56,6 @@
 #define RBD_MINORS_PER_MAJOR	256		/* max minors per blkdev */

 #define RBD_MAX_MD_NAME_LEN	(RBD_MAX_OBJ_NAME_LEN + sizeof(RBD_SUFFIX))
-#define RBD_MAX_POOL_NAME_LEN	64
 #define RBD_MAX_SNAP_NAME_LEN	32
 #define RBD_MAX_OPT_LEN		1024

@@ -166,8 +165,7 @@ struct rbd_device {
 	char			obj[RBD_MAX_OBJ_NAME_LEN]; /* rbd image name */
 	int			obj_len;
 	char			obj_md_name[RBD_MAX_MD_NAME_LEN]; /* hdr nm. */
-	char			pool_name[RBD_MAX_POOL_NAME_LEN];
-	int			poolid;
+	int			pool_id;

 	struct ceph_osd_event   *watch_event;
 	struct ceph_osd_request *watch_request;
@@ -930,7 +928,7 @@ static int rbd_do_request(struct request *rq,
 	layout->fl_stripe_unit = cpu_to_le32(1 << RBD_MAX_OBJ_ORDER);
 	layout->fl_stripe_count = cpu_to_le32(1);
 	layout->fl_object_size = cpu_to_le32(1 << RBD_MAX_OBJ_ORDER);
-	layout->fl_pg_pool = cpu_to_le32(dev->poolid);
+	layout->fl_pg_pool = cpu_to_le32(dev->pool_id);
 	ceph_calc_raw_layout(osdc, layout, snapid, ofs, &len, &bno,
 				req, ops);

@@ -1653,7 +1651,7 @@ static int rbd_header_add_snap(struct rbd_device *dev,
 		return -EINVAL;

 	monc = &dev->rbd_client->client->monc;
-	ret = ceph_monc_create_snapid(monc, dev->poolid, &new_snapid);
+	ret = ceph_monc_create_snapid(monc, dev->pool_id, &new_snapid);
 	dout("created snapid=%lld\n", new_snapid);
 	if (ret < 0)
 		return ret;
@@ -1851,12 +1849,12 @@ static ssize_t rbd_client_id_show(struct device
*dev,
 			ceph_client_id(rbd_dev->rbd_client->client));
 }

-static ssize_t rbd_pool_show(struct device *dev,
+static ssize_t rbd_pool_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->pool_name);
+	return sprintf(buf, "%d\n", rbd_dev->pool_id);
 }

 static ssize_t rbd_name_show(struct device *dev,
@@ -1898,7 +1896,7 @@ static ssize_t rbd_image_refresh(struct device *dev,
 static DEVICE_ATTR(size, S_IRUGO, rbd_size_show, NULL);
 static DEVICE_ATTR(major, S_IRUGO, rbd_major_show, NULL);
 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(refresh, S_IWUSR, NULL, rbd_image_refresh);
 static DEVICE_ATTR(current_snap, S_IRUGO, rbd_snap_show, NULL);
@@ -1908,7 +1906,7 @@ static struct attribute *rbd_attrs[] = {
 	&dev_attr_size.attr,
 	&dev_attr_major.attr,
 	&dev_attr_client_id.attr,
-	&dev_attr_pool.attr,
+	&dev_attr_pool_id.attr,
 	&dev_attr_name.attr,
 	&dev_attr_current_snap.attr,
 	&dev_attr_refresh.attr,
@@ -2329,25 +2327,31 @@ static inline char *dup_token(const char **buf,
size_t *lenp)
 }

 /*
- * This fills in the pool_name, obj, obj_len, snap_name, obj_len,
- * rbd_dev, rbd_md_name, and name fields of the given rbd_dev, based
- * on the list of monitor addresses and other options provided via
- * /sys/bus/rbd/add.
+ * This fills in the obj, obj_len, snap_name, rbd_dev, rbd_md_name,
+ * and name fields of the given rbd_dev, based on the list of
+ * monitor addresses and other options provided via /sys/bus/rbd/add.
+ *
+ * Returns a pointer to a dynamically-allocated buffer containing
+ * the pool name provided, or a pointer-coded errno if an error
+ * occurs.
  */
-static int rbd_add_parse_args(struct rbd_device *rbd_dev,
+static char *rbd_add_parse_args(struct rbd_device *rbd_dev,
 			      const char *buf,
 			      const char **mon_addrs,
 			      size_t *mon_addrs_size,
 			      char *options,
 			      size_t options_size)
 {
-	size_t	len;
+	size_t len;
+	int ret = -EINVAL;
+	char *pool_name = NULL;

 	/* The first four tokens are required */

 	len = next_token(&buf);
 	if (!len)
-		return -EINVAL;
+		goto out_err;
+
 	*mon_addrs_size = len + 1;
 	*mon_addrs = buf;

@@ -2355,15 +2359,17 @@ static int rbd_add_parse_args(struct rbd_device
*rbd_dev,

 	len = copy_token(&buf, options, options_size);
 	if (!len || len >= options_size)
-		return -EINVAL;
+		goto out_err;

-	len = copy_token(&buf, rbd_dev->pool_name, sizeof (rbd_dev->pool_name));
-	if (!len || len >= sizeof (rbd_dev->pool_name))
-		return -EINVAL;
+	pool_name = dup_token(&buf, NULL);
+	if (!pool_name) {
+		ret = -ENOMEM;
+		goto out_err;
+	}

 	len = copy_token(&buf, rbd_dev->obj, sizeof (rbd_dev->obj));
 	if (!len || len >= sizeof (rbd_dev->obj))
-		return -EINVAL;
+		goto out_err;

 	/* We have the object length in hand, save it. */

@@ -2382,9 +2388,14 @@ static int rbd_add_parse_args(struct rbd_device
*rbd_dev,
 		memcpy(rbd_dev->snap_name, RBD_SNAP_HEAD_NAME,
 			sizeof (RBD_SNAP_HEAD_NAME));
 	else if (len >= sizeof (rbd_dev->snap_name))
-		return -EINVAL;
+		goto out_err;

-	return 0;
+	return pool_name;
+
+out_err:
+	kfree(pool_name);
+
+	return ERR_PTR(ret);
 }

 static ssize_t rbd_add(struct bus_type *bus,
@@ -2396,6 +2407,7 @@ static ssize_t rbd_add(struct bus_type *bus,
 	size_t mon_addrs_size = 0;
 	char *options = NULL;
 	struct ceph_osd_client *osdc;
+	char *pool_name;
 	int rc = -ENOMEM;

 	if (!try_module_get(THIS_MODULE))
@@ -2425,10 +2437,14 @@ static ssize_t rbd_add(struct bus_type *bus,
 	sprintf(rbd_dev->name, "%s%d", RBD_DRV_NAME, rbd_dev->id);

 	/* parse add command */
-	rc = rbd_add_parse_args(rbd_dev, buf, &mon_addrs, &mon_addrs_size,
-				options, count);
-	if (rc)
+	pool_name = rbd_add_parse_args(rbd_dev, buf,
+					&mon_addrs, &mon_addrs_size,
+					options, count);
+	if (IS_ERR(pool_name)) {
+		rc = PTR_ERR(pool_name);
+		pool_name = NULL;
 		goto err_put_id;
+	}

 	rbd_dev->rbd_client = rbd_get_client(mon_addrs, mon_addrs_size - 1,
 						options);
@@ -2439,10 +2455,10 @@ static ssize_t rbd_add(struct bus_type *bus,

 	/* pick the pool */
 	osdc = &rbd_dev->rbd_client->client->osdc;
-	rc = ceph_pg_poolid_by_name(osdc->osdmap, rbd_dev->pool_name);
+	rc = ceph_pg_poolid_by_name(osdc->osdmap, pool_name);
 	if (rc < 0)
 		goto err_out_client;
-	rbd_dev->poolid = rc;
+	rbd_dev->pool_id = rc;

 	/* register our block device */
 	rc = register_blkdev(0, rbd_dev->name);
@@ -2453,6 +2469,7 @@ static ssize_t rbd_add(struct bus_type *bus,
 	rc = rbd_bus_add_dev(rbd_dev);
 	if (rc)
 		goto err_out_blkdev;
+	kfree(pool_name);

 	/*
 	 * At this point cleanup in the event of an error is the job
@@ -2482,6 +2499,7 @@ err_out_blkdev:
 err_out_client:
 	rbd_put_client(rbd_dev);
 err_put_id:
+	kfree(pool_name);
 	rbd_id_put(rbd_dev);
 err_nomem:
 	kfree(options);
-- 
1.7.5.4