1 files changed, 49 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e0160607e6e2..d32660ce753d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2492,6 +2492,11 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
         key.type = BTRFS_CHUNK_ITEM_KEY;
 
         while (1) {
+                if (atomic_read(&fs_info->balance_pause_req)) {
+                        ret = -ECANCELED;
+                        goto error;
+                }
+
                 ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
                 if (ret < 0)
                         goto error;
@@ -2553,6 +2558,11 @@ error:
         return ret;
 }
 
+static inline int balance_need_close(struct btrfs_fs_info *fs_info)
+{
+        return atomic_read(&fs_info->balance_pause_req) == 0;
+}
+
 static void __cancel_balance(struct btrfs_fs_info *fs_info)
 {
         int ret;
@@ -2575,7 +2585,8 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
         u64 allowed;
         int ret;
 
-        if (btrfs_fs_closing(fs_info)) {
+        if (btrfs_fs_closing(fs_info) ||
+            atomic_read(&fs_info->balance_pause_req)) {
                 ret = -EINVAL;
                 goto out;
         }
@@ -2680,18 +2691,25 @@ do_balance:
                 spin_unlock(&fs_info->balance_lock);
         }
 
+        atomic_inc(&fs_info->balance_running);
         mutex_unlock(&fs_info->balance_mutex);
 
         ret = __btrfs_balance(fs_info);
 
         mutex_lock(&fs_info->balance_mutex);
+        atomic_dec(&fs_info->balance_running);
 
         if (bargs) {
                 memset(bargs, 0, sizeof(*bargs));
                 update_ioctl_balance_args(fs_info, bargs);
         }
 
-        __cancel_balance(fs_info);
+        if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
+            balance_need_close(fs_info)) {
+                __cancel_balance(fs_info);
+        }
+
+        wake_up(&fs_info->balance_wait_q);
 
         return ret;
 out:
@@ -2785,6 +2803,35 @@ out:
         return ret;
 }
 
+int btrfs_pause_balance(struct btrfs_fs_info *fs_info)
+{
+        int ret = 0;
+
+        mutex_lock(&fs_info->balance_mutex);
+        if (!fs_info->balance_ctl) {
+                mutex_unlock(&fs_info->balance_mutex);
+                return -ENOTCONN;
+        }
+
+        if (atomic_read(&fs_info->balance_running)) {
+                atomic_inc(&fs_info->balance_pause_req);
+                mutex_unlock(&fs_info->balance_mutex);
+
+                wait_event(fs_info->balance_wait_q,
+                           atomic_read(&fs_info->balance_running) == 0);
+
+                mutex_lock(&fs_info->balance_mutex);
+                /* we are good with balance_ctl ripped off from under us */
+                BUG_ON(atomic_read(&fs_info->balance_running));
+                atomic_dec(&fs_info->balance_pause_req);
+        } else {
+                ret = -ENOTCONN;
+        }
+
+        mutex_unlock(&fs_info->balance_mutex);
+        return ret;
+}
+
 /*
  * shrinking a device means finding all of the device extents past
  * the new size, and then following the back refs to the chunks.