1 files changed, 7 insertions, 18 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 3ec85dfce124..8a86b62466f7 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2098,32 +2098,26 @@ static void rbd_dev_parent_put(struct rbd_device *rbd_dev)
  * If an image has a non-zero parent overlap, get a reference to its
  * parent.
  *
- * We must get the reference before checking for the overlap to
- * coordinate properly with zeroing the parent overlap in
- * rbd_dev_v2_parent_info() when an image gets flattened.  We
- * drop it again if there is no overlap.
- *
  * Returns true if the rbd device has a parent with a non-zero
  * overlap and a reference for it was successfully taken, or
  * false otherwise.
  */
 static bool rbd_dev_parent_get(struct rbd_device *rbd_dev)
 {
-        int counter;
+        int counter = 0;
 
         if (!rbd_dev->parent_spec)
                 return false;
 
-        counter = atomic_inc_return_safe(&rbd_dev->parent_ref);
-        if (counter > 0 && rbd_dev->parent_overlap)
-                return true;
-
-        /* Image was flattened, but parent is not yet torn down */
+        down_read(&rbd_dev->header_rwsem);
+        if (rbd_dev->parent_overlap)
+                counter = atomic_inc_return_safe(&rbd_dev->parent_ref);
+        up_read(&rbd_dev->header_rwsem);
 
         if (counter < 0)
                 rbd_warn(rbd_dev, "parent reference overflow");
 
-        return false;
+        return counter > 0;
 }
 
 /*
@@ -4239,7 +4233,6 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
                  */
                 if (rbd_dev->parent_overlap) {
                         rbd_dev->parent_overlap = 0;
-                        smp_mb();
                         rbd_dev_parent_put(rbd_dev);
                         pr_info("%s: clone image has been flattened\n",
                                 rbd_dev->disk->disk_name);
@@ -4285,7 +4278,6 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev)
          * treat it specially.
          */
         rbd_dev->parent_overlap = overlap;
-        smp_mb();
         if (!overlap) {
 
                 /* A null parent_spec indicates it's the initial probe */
@@ -5114,10 +5106,7 @@ static void rbd_dev_unprobe(struct rbd_device *rbd_dev)
 {
         struct rbd_image_header *header;
 
-        /* Drop parent reference unless it's already been done (or none) */
-
-        if (rbd_dev->parent_overlap)
-                rbd_dev_parent_put(rbd_dev);
+        rbd_dev_parent_put(rbd_dev);
 
         /* Free dynamic fields from the header, then zero it out */