1 files changed, 47 insertions, 1 deletions

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index bcc2ad4f0899..bac464f0bc59 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1245,6 +1245,50 @@ err:
 }
 
 /*
+ * Grab the exclusive iolock for a data copy from src to dest, making
+ * sure to abide vfs locking order (lowest pointer value goes first) and
+ * breaking the pnfs layout leases on dest before proceeding.  The loop
+ * is needed because we cannot call the blocking break_layout() with the
+ * src iolock held, and therefore have to back out both locks.
+ */
+static int
+xfs_iolock_two_inodes_and_break_layout(
+        struct inode            *src,
+        struct inode            *dest)
+{
+        int                     error;
+
+retry:
+        if (src < dest) {
+                inode_lock(src);
+                inode_lock_nested(dest, I_MUTEX_NONDIR2);
+        } else {
+                /* src >= dest */
+                inode_lock(dest);
+        }
+
+        error = break_layout(dest, false);
+        if (error == -EWOULDBLOCK) {
+                inode_unlock(dest);
+                if (src < dest)
+                        inode_unlock(src);
+                error = break_layout(dest, true);
+                if (error)
+                        return error;
+                goto retry;
+        }
+        if (error) {
+                inode_unlock(dest);
+                if (src < dest)
+                        inode_unlock(src);
+                return error;
+        }
+        if (src > dest)
+                inode_lock_nested(src, I_MUTEX_NONDIR2);
+        return 0;
+}
+
+/*
  * Link a range of blocks from one file to another.
  */
 int
@@ -1274,7 +1318,9 @@ xfs_reflink_remap_range(
                 return -EIO;
 
         /* Lock both files against IO */
-        lock_two_nondirectories(inode_in, inode_out);
+        ret = xfs_iolock_two_inodes_and_break_layout(inode_in, inode_out);
+        if (ret)
+                return ret;
         if (same_inode)
                 xfs_ilock(src, XFS_MMAPLOCK_EXCL);
         else