xfs: fix xfs_bunmapi to allow unmapping of partial rt extents

Source kernel commit: 2b6a5ec26887cba195022286b039f2cc0ec683b1

When XFS_BMAPI_REMAP is passed to bunmapi, that means that we want to
remove part of a block mapping without touching the allocator.  For
realtime files with rtextsize > 1, that also means that we should skip
all the code that changes a partial remove request into an unwritten
extent conversion.  IOWs, bunmapi in this mode should handle removing
the mapping from the rt file and nothing else.

Note that XFS_BMAPI_REMAP callers are required to decrement the
reference count and/or free the space manually.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>

diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index 07bd8b34635a2a8a1086db7900339b7ea96ad1b1..38855091283c97c67669408bbb3e578bc07f82c2 100644 (file)
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -5453,7 +5453,7 @@ __xfs_bunmapi(
                if (del.br_startoff + del.br_blockcount > end + 1)
                        del.br_blockcount = end + 1 - del.br_startoff;
 
-               if (!isrt)
+               if (!isrt || (flags & XFS_BMAPI_REMAP))
                        goto delete;
 
                mod = xfs_rtb_to_rtxoff(mp,
@@ -5471,7 +5471,7 @@ __xfs_bunmapi(
                                 * This piece is unwritten, or we're not
                                 * using unwritten extents.  Skip over it.
                                 */
-                               ASSERT(end >= mod);
+                               ASSERT((flags & XFS_BMAPI_REMAP) || end >= mod);
                                end -= mod > del.br_blockcount ?
                                        del.br_blockcount : mod;
                                if (end < got.br_startoff &&