rbd: always set read-only flag in rbd_add()

Hold off setting the read-only flag in rbd_add() for an image being
mapped until we have successfully probed the image.  At that point
we know whether it's a snapshot mapping or not, so we can set the
read-only flag in that one place rather than doing so (for
snapshots) in rbd_dev_mapping_set().  To do this, pass a flag to the
image probe routine indicating whether we want a read-only mapping.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index a62e59a0aea7e3480a858502a3335a916b74d2db..b5cac7931ffc87ef7c1c8eb3394cf22c7a0df406 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -359,7 +359,7 @@ static ssize_t rbd_add(struct bus_type *bus, const char *buf,
                       size_t count);
 static ssize_t rbd_remove(struct bus_type *bus, const char *buf,
                          size_t count);
-static int rbd_dev_image_probe(struct rbd_device *rbd_dev);
+static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool read_only);
 
 static struct bus_attribute rbd_bus_attrs[] = {
        __ATTR(add, S_IWUSR, NULL, rbd_add),
@@ -951,11 +951,6 @@ static int rbd_dev_mapping_set(struct rbd_device *rbd_dev)
        rbd_dev->mapping.size = size;
        rbd_dev->mapping.features = features;
 
-       /* If we are mapping a snapshot it must be marked read-only */
-
-       if (snap_id != CEPH_NOSNAP)
-               rbd_dev->mapping.read_only = true;
-
        return 0;
 }
 
@@ -963,7 +958,6 @@ static void rbd_dev_mapping_clear(struct rbd_device *rbd_dev)
 {
        rbd_dev->mapping.size = 0;
        rbd_dev->mapping.features = 0;
-       rbd_dev->mapping.read_only = true;
 }
 
 static const char *rbd_segment_name(struct rbd_device *rbd_dev, u64 offset)
@@ -4620,7 +4614,7 @@ static int rbd_dev_probe_parent(struct rbd_device *rbd_dev)
        if (!parent)
                goto out_err;
 
-       ret = rbd_dev_image_probe(parent);
+       ret = rbd_dev_image_probe(parent, true);
        if (ret < 0)
                goto out_err;
        rbd_dev->parent = parent;
@@ -4743,7 +4737,7 @@ static void rbd_dev_image_release(struct rbd_device *rbd_dev)
  * device.  For format 2 images this includes determining the image
  * id.
  */
-static int rbd_dev_image_probe(struct rbd_device *rbd_dev)
+static int rbd_dev_image_probe(struct rbd_device *rbd_dev, bool read_only)
 {
        int ret;
        int tmp;
@@ -4778,6 +4772,12 @@ static int rbd_dev_image_probe(struct rbd_device *rbd_dev)
        if (ret)
                goto err_out_probe;
 
+       /* If we are mapping a snapshot it must be marked read-only */
+
+       if (rbd_dev->spec->snap_id != CEPH_NOSNAP)
+               read_only = true;
+       rbd_dev->mapping.read_only = read_only;
+
        ret = rbd_dev_probe_parent(rbd_dev);
        if (!ret)
                return 0;
@@ -4811,6 +4811,7 @@ static ssize_t rbd_add(struct bus_type *bus,
        struct rbd_spec *spec = NULL;
        struct rbd_client *rbdc;
        struct ceph_osd_client *osdc;
+       bool read_only;
        int rc = -ENOMEM;
 
        if (!try_module_get(THIS_MODULE))
@@ -4820,6 +4821,9 @@ static ssize_t rbd_add(struct bus_type *bus,
        rc = rbd_add_parse_args(buf, &ceph_opts, &rbd_opts, &spec);
        if (rc < 0)
                goto err_out_module;
+       read_only = rbd_opts->read_only;
+       kfree(rbd_opts);
+       rbd_opts = NULL;        /* done with this */
 
        rbdc = rbd_get_client(ceph_opts);
        if (IS_ERR(rbdc)) {
@@ -4850,11 +4854,7 @@ static ssize_t rbd_add(struct bus_type *bus,
        rbdc = NULL;            /* rbd_dev now owns this */
        spec = NULL;            /* rbd_dev now owns this */
 
-       rbd_dev->mapping.read_only = rbd_opts->read_only;
-       kfree(rbd_opts);
-       rbd_opts = NULL;        /* done with this */
-
-       rc = rbd_dev_image_probe(rbd_dev);
+       rc = rbd_dev_image_probe(rbd_dev, read_only);
        if (rc < 0)
                goto err_out_rbd_dev;