rbd: clean up a few things in the refresh path

This includes a few relatively small fixes I found while examining
the code that refreshes image information.

This resolves:
    http://tracker.ceph.com/issues/5040

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 cb728a01a19f2c5981fe98896ae42612c2798f06..d4902c52bf2673ddbceea8224667b88dce976a8a 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2860,7 +2860,7 @@ static void rbd_watch_cb(u64 ver, u64 notify_id, u8 opcode, void *data)
                (unsigned int)opcode);
        ret = rbd_dev_refresh(rbd_dev);
        if (ret)
-               rbd_warn(rbd_dev, ": header refresh error (%d)\n", ret);
+               rbd_warn(rbd_dev, "header refresh error (%d)\n", ret);
 
        rbd_obj_notify_ack(rbd_dev, notify_id);
 }
@@ -3340,8 +3340,8 @@ static int rbd_dev_refresh(struct rbd_device *rbd_dev)
        int ret;
 
        rbd_assert(rbd_image_format_valid(rbd_dev->image_format));
-       mapping_size = rbd_dev->mapping.size;
        mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
+       mapping_size = rbd_dev->mapping.size;
        if (rbd_dev->image_format == 1)
                ret = rbd_dev_v1_header_info(rbd_dev);
        else
@@ -3814,6 +3814,7 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
        void *end;
        u64 pool_id;
        char *image_id;
+       u64 snap_id;
        u64 overlap;
        int ret;
 
@@ -3873,24 +3874,56 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
                        (unsigned long long)pool_id, U32_MAX);
                goto out_err;
        }
-       parent_spec->pool_id = pool_id;
 
        image_id = ceph_extract_encoded_string(&p, end, NULL, 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, snap_id, out_err);
        ceph_decode_64_safe(&p, end, overlap, out_err);
 
-       if (overlap) {
-               rbd_spec_put(rbd_dev->parent_spec);
+       /*
+        * The parent won't change (except when the clone is
+        * flattened, already handled that).  So we only need to
+        * record the parent spec we have not already done so.
+        */
+       if (!rbd_dev->parent_spec) {
+               parent_spec->pool_id = pool_id;
+               parent_spec->image_id = image_id;
+               parent_spec->snap_id = snap_id;
                rbd_dev->parent_spec = parent_spec;
                parent_spec = NULL;     /* rbd_dev now owns this */
-               rbd_dev->parent_overlap = overlap;
-       } else {
-               rbd_warn(rbd_dev, "ignoring parent of clone with overlap 0\n");
+       }
+
+       /*
+        * We always update the parent overlap.  If it's zero we
+        * treat it specially.
+        */
+       rbd_dev->parent_overlap = overlap;
+       smp_mb();
+       if (!overlap) {
+
+               /* A null parent_spec indicates it's the initial probe */
+
+               if (parent_spec) {
+                       /*
+                        * The overlap has become zero, so the clone
+                        * must have been resized down to 0 at some
+                        * point.  Treat this the same as a flatten.
+                        */
+                       rbd_dev_parent_put(rbd_dev);
+                       pr_info("%s: clone image now standalone\n",
+                               rbd_dev->disk->disk_name);
+               } else {
+                       /*
+                        * For the initial probe, if we find the
+                        * overlap is zero we just pretend there was
+                        * no parent image.
+                        */
+                       rbd_warn(rbd_dev, "ignoring parent of "
+                                               "clone with overlap 0\n");
+               }
        }
 out:
        ret = 0;