dm thin metadata: remove incorrect close_device on creation error paths

The __open_device() error paths in __create_thin() and __create_snap()
incorrectly call __close_device() even if td was not initialized by
__open_device().  Remove this.

Also document __open_device() return values, remove a redundant
td->changed = 1 in __create_thin(), and insert an additional
safeguard against creating an already-existing device.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 17 insertions, 5 deletions

diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 59c4f0446ffa..13d964636d57 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -789,6 +789,11 @@ int dm_pool_metadata_close(struct dm_pool_metadata *pmd)
         return 0;
 }
 
+/*
+ * __open_device: Returns @td corresponding to device with id @dev,
+ * creating it if @create is set and incrementing @td->open_count.
+ * On failure, @td is undefined.
+ */
 static int __open_device(struct dm_pool_metadata *pmd,
                          dm_thin_id dev, int create,
                          struct dm_thin_device **td)
@@ -799,10 +804,16 @@ static int __open_device(struct dm_pool_metadata *pmd,
         struct disk_device_details details_le;
 
         /*
-         * Check the device isn't already open.
+         * If the device is already open, return it.
          */
         list_for_each_entry(td2, &pmd->thin_devices, list)
                 if (td2->id == dev) {
+                        /*
+                         * May not create an already-open device.
+                         */
+                        if (create)
+                                return -EEXIST;
+
                         td2->open_count++;
                         *td = td2;
                         return 0;
@@ -817,6 +828,9 @@ static int __open_device(struct dm_pool_metadata *pmd,
                 if (r != -ENODATA || !create)
                         return r;
 
+                /*
+                 * Create new device.
+                 */
                 changed = 1;
                 details_le.mapped_blocks = 0;
                 details_le.transaction_id = cpu_to_le64(pmd->trans_id);
@@ -882,12 +896,10 @@ static int __create_thin(struct dm_pool_metadata *pmd,
 
         r = __open_device(pmd, dev, 1, &td);
         if (r) {
-                __close_device(td);
                 dm_btree_remove(&pmd->tl_info, pmd->root, &key, &pmd->root);
                 dm_btree_del(&pmd->bl_info, dev_root);
                 return r;
         }
-        td->changed = 1;
         __close_device(td);
 
         return r;
@@ -967,14 +979,14 @@ static int __create_snap(struct dm_pool_metadata *pmd,
                 goto bad;
 
         r = __set_snapshot_details(pmd, td, origin, pmd->time);
+        __close_device(td);
+
         if (r)
                 goto bad;
 
-        __close_device(td);
         return 0;
 
 bad:
-        __close_device(td);
         dm_btree_remove(&pmd->tl_info, pmd->root, &key, &pmd->root);
         dm_btree_remove(&pmd->details_info, pmd->details_root,
                         &key, &pmd->details_root);