1 files changed, 48 insertions, 3 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3e2c7c738f23..35af93355063 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2622,7 +2622,18 @@ static noinline int find_free_extent(struct btrfs_trans_handle *trans,
                                                        search_start);
                 if (block_group && block_group_bits(block_group, data)) {
                         down_read(&space_info->groups_sem);
-                        goto have_block_group;
+                        if (list_empty(&block_group->list) ||
+                            block_group->ro) {
+                                /*
+                                 * someone is removing this block group,
+                                 * we can't jump into the have_block_group
+                                 * target because our list pointers are not
+                                 * valid
+                                 */
+                                btrfs_put_block_group(block_group);
+                                up_read(&space_info->groups_sem);
+                        } else
+                                goto have_block_group;
                 } else if (block_group) {
                         btrfs_put_block_group(block_group);
                 }
@@ -2656,6 +2667,13 @@ have_block_group:
                          * people trying to start a new cluster
                          */
                         spin_lock(&last_ptr->refill_lock);
+                        if (last_ptr->block_group &&
+                            (last_ptr->block_group->ro ||
+                            !block_group_bits(last_ptr->block_group, data))) {
+                                offset = 0;
+                                goto refill_cluster;
+                        }
+
                         offset = btrfs_alloc_from_cluster(block_group, last_ptr,
                                                  num_bytes, search_start);
                         if (offset) {
@@ -2681,10 +2699,17 @@ have_block_group:
 
                                 last_ptr_loop = 1;
                                 search_start = block_group->key.objectid;
+                                /*
+                                 * we know this block group is properly
+                                 * in the list because
+                                 * btrfs_remove_block_group, drops the
+                                 * cluster before it removes the block
+                                 * group from the list
+                                 */
                                 goto have_block_group;
                         }
                         spin_unlock(&last_ptr->lock);
-
+refill_cluster:
                         /*
                          * this cluster didn't work out, free it and
                          * start over
@@ -5968,6 +5993,7 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 {
         struct btrfs_path *path;
         struct btrfs_block_group_cache *block_group;
+        struct btrfs_free_cluster *cluster;
         struct btrfs_key key;
         int ret;
 
@@ -5979,6 +6005,21 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 
         memcpy(&key, &block_group->key, sizeof(key));
 
+        /* make sure this block group isn't part of an allocation cluster */
+        cluster = &root->fs_info->data_alloc_cluster;
+        spin_lock(&cluster->refill_lock);
+        btrfs_return_cluster_to_free_space(block_group, cluster);
+        spin_unlock(&cluster->refill_lock);
+
+        /*
+         * make sure this block group isn't part of a metadata
+         * allocation cluster
+         */
+        cluster = &root->fs_info->meta_alloc_cluster;
+        spin_lock(&cluster->refill_lock);
+        btrfs_return_cluster_to_free_space(block_group, cluster);
+        spin_unlock(&cluster->refill_lock);
+
         path = btrfs_alloc_path();
         BUG_ON(!path);
 
@@ -5988,7 +6029,11 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
         spin_unlock(&root->fs_info->block_group_cache_lock);
         btrfs_remove_free_space_cache(block_group);
         down_write(&block_group->space_info->groups_sem);
-        list_del(&block_group->list);
+        /*
+         * we must use list_del_init so people can check to see if they
+         * are still on the list after taking the semaphore
+         */
+        list_del_init(&block_group->list);
         up_write(&block_group->space_info->groups_sem);
 
         spin_lock(&block_group->space_info->lock);