1 files changed, 13 insertions, 0 deletions

diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
index 3b9582c60a22..e60490bc00a6 100644
--- a/fs/xfs/xfs_dfrag.c
+++ b/fs/xfs/xfs_dfrag.c
@@ -377,6 +377,19 @@ xfs_swap_extents(
         ip->i_d.di_format = tip->i_d.di_format;
         tip->i_d.di_format = tmp;
 
+        /*
+         * The extents in the source inode could still contain speculative
+         * preallocation beyond EOF (e.g. the file is open but not modified
+         * while defrag is in progress). In that case, we need to copy over the
+         * number of delalloc blocks the data fork in the source inode is
+         * tracking beyond EOF so that when the fork is truncated away when the
+         * temporary inode is unlinked we don't underrun the i_delayed_blks
+         * counter on that inode.
+         */
+        ASSERT(tip->i_delayed_blks == 0);
+        tip->i_delayed_blks = ip->i_delayed_blks;
+        ip->i_delayed_blks = 0;
+
         ilf_fields = XFS_ILOG_CORE;
 
         switch(ip->i_d.di_format) {