[PATCH 19/71] xfs: adjust refcount when unmapping file blocks

["Darrick J. Wong" <darrick.wong@xxxxxxxxxx>]

When we're unmapping blocks from a reflinked file, decrease the
refcount of the affected blocks and free the extents that are no
longer in use.

v2: Use deferred ops system to avoid deadlocks and running out of
transaction reservation.

Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
 fs/xfs/libxfs/xfs_bmap.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)


diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 042d7bf..5e0c9ec 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -48,6 +48,7 @@
 #include "xfs_filestream.h"
 #include "xfs_rmap.h"
 #include "xfs_ag_resv.h"
+#include "xfs_refcount.h"
 
 
 kmem_zone_t            *xfs_bmap_free_item_zone;
@@ -5062,9 +5063,16 @@ xfs_bmap_del_extent(
        /*
         * If we need to, add to list of extents to delete.
         */
-       if (do_fx)
-               xfs_bmap_add_free(mp, dfops, del->br_startblock,
-                               del->br_blockcount, NULL);
+       if (do_fx) {
+               if (xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK) {
+                       error = xfs_refcount_decrease_extent(mp, dfops, del);
+                       if (error)
+                               goto done;
+               } else
+                       xfs_bmap_add_free(mp, dfops, del->br_startblock,
+                                       del->br_blockcount, NULL);
+       }
+
        /*
         * Adjust inode # blocks in the file.
         */