1 files changed, 37 insertions, 6 deletions

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 115a7cd3a6fb..63f814872dfb 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -753,14 +753,13 @@ xfs_initialize_perag_data(
 }
 
 /*
- * xfs_mod_sb() can be used to copy arbitrary changes to the
- * in-core superblock into the superblock buffer to be logged.
- * It does not provide the higher level of locking that is
- * needed to protect the in-core superblock from concurrent
- * access.
+ * xfs_log_sb() can be used to copy arbitrary changes to the in-core superblock
+ * into the superblock buffer to be logged.  It does not provide the higher
+ * level of locking that is needed to protect the in-core superblock from
+ * concurrent access.
  */
 void
-xfs_mod_sb(
+xfs_log_sb(
         struct xfs_trans        *tp)
 {
         struct xfs_mount        *mp = tp->t_mountp;
@@ -770,3 +769,35 @@ xfs_mod_sb(
         xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
         xfs_trans_log_buf(tp, bp, 0, sizeof(struct xfs_dsb));
 }
+
+/*
+ * xfs_sync_sb
+ *
+ * Sync the superblock to disk.
+ *
+ * Note that the caller is responsible for checking the frozen state of the
+ * filesystem. This procedure uses the non-blocking transaction allocator and
+ * thus will allow modifications to a frozen fs. This is required because this
+ * code can be called during the process of freezing where use of the high-level
+ * allocator would deadlock.
+ */
+int
+xfs_sync_sb(
+        struct xfs_mount        *mp,
+        bool                    wait)
+{
+        struct xfs_trans        *tp;
+        int                     error;
+
+        tp = _xfs_trans_alloc(mp, XFS_TRANS_SB_CHANGE, KM_SLEEP);
+        error = xfs_trans_reserve(tp, &M_RES(mp)->tr_sb, 0, 0);
+        if (error) {
+                xfs_trans_cancel(tp, 0);
+                return error;
+        }
+
+        xfs_log_sb(tp);
+        if (wait)
+                xfs_trans_set_sync(tp);
+        return xfs_trans_commit(tp, 0);
+}