4 files changed, 36 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index a365400e38da..e36e97b473a8 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1613,6 +1613,7 @@ struct btrfs_fs_info {
         struct mutex qgroup_rescan_lock; /* protects the progress item */
         struct btrfs_key qgroup_rescan_progress;
         struct btrfs_workers qgroup_rescan_workers;
+        struct completion qgroup_rescan_completion;
 
         /* filesystem state */
         unsigned long fs_state;
@@ -3820,6 +3821,7 @@ int btrfs_quota_enable(struct btrfs_trans_handle *trans,
 int btrfs_quota_disable(struct btrfs_trans_handle *trans,
                         struct btrfs_fs_info *fs_info);
 int btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info);
+int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info);
 int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
                               struct btrfs_fs_info *fs_info, u64 src, u64 dst);
 int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0f81d67cdc8d..1e0dda1feefe 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3937,6 +3937,16 @@ static long btrfs_ioctl_quota_rescan_status(struct file *file, void __user *arg)
         return ret;
 }
 
+static long btrfs_ioctl_quota_rescan_wait(struct file *file, void __user *arg)
+{
+        struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        return btrfs_qgroup_wait_for_completion(root->fs_info);
+}
+
 static long btrfs_ioctl_set_received_subvol(struct file *file,
                                             void __user *arg)
 {
@@ -4179,6 +4189,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_quota_rescan(file, argp);
         case BTRFS_IOC_QUOTA_RESCAN_STATUS:
                 return btrfs_ioctl_quota_rescan_status(file, argp);
+        case BTRFS_IOC_QUOTA_RESCAN_WAIT:
+                return btrfs_ioctl_quota_rescan_wait(file, argp);
         case BTRFS_IOC_DEV_REPLACE:
                 return btrfs_ioctl_dev_replace(root, argp);
         case BTRFS_IOC_GET_FSLABEL:
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 7f38cce2528d..d059d86c3131 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2070,6 +2070,8 @@ out:
         } else {
                 pr_err("btrfs: qgroup scan failed with %d\n", err);
         }
+
+        complete_all(&fs_info->qgroup_rescan_completion);
 }
 
 static void
@@ -2110,6 +2112,7 @@ btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
         fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_RESCAN;
         memset(&fs_info->qgroup_rescan_progress, 0,
                 sizeof(fs_info->qgroup_rescan_progress));
+        init_completion(&fs_info->qgroup_rescan_completion);
 
         /* clear all current qgroup tracking information */
         for (n = rb_first(&fs_info->qgroup_tree); n; n = rb_next(n)) {
@@ -2126,3 +2129,21 @@ btrfs_qgroup_rescan(struct btrfs_fs_info *fs_info)
 
         return 0;
 }
+
+int btrfs_qgroup_wait_for_completion(struct btrfs_fs_info *fs_info)
+{
+        int running;
+        int ret = 0;
+
+        mutex_lock(&fs_info->qgroup_rescan_lock);
+        spin_lock(&fs_info->qgroup_lock);
+        running = fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_RESCAN;
+        spin_unlock(&fs_info->qgroup_lock);
+        mutex_unlock(&fs_info->qgroup_rescan_lock);
+
+        if (running)
+                ret = wait_for_completion_interruptible(
+                                        &fs_info->qgroup_rescan_completion);
+
+        return ret;
+}
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 5ef0df545a2a..5b683b5f63cd 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -530,6 +530,7 @@ struct btrfs_ioctl_send_args {
                                struct btrfs_ioctl_quota_rescan_args)
 #define BTRFS_IOC_QUOTA_RESCAN_STATUS _IOR(BTRFS_IOCTL_MAGIC, 45, \
                                struct btrfs_ioctl_quota_rescan_args)
+#define BTRFS_IOC_QUOTA_RESCAN_WAIT _IO(BTRFS_IOCTL_MAGIC, 46)
 #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 49, \
                                    char[BTRFS_LABEL_SIZE])
 #define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 50, \