xfs: use realtime EFI to free extents when rtgroups are enabled

When rmap is enabled, XFS expects a certain order of operations, which
is: 1) remove the file mapping, 2) remove the reverse mapping, and then
3) free the blocks.  When reflink is enabled, XFS replaces (3) with a
deferred refcount decrement operation that can schedule freeing the
blocks if that was the last refcount.

For realtime files, xfs_bmap_del_extent_real tries to do 1 and 3 in the
same transaction, which will break both rmap and reflink unless we
switch it to use realtime EFIs.  Both rmap and reflink depend on the
rtgroups feature, so let's turn on EFIs for all rtgroups filesystems.

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

Author: Darrick J. Wong

fs/xfs/libxfs/xfs_bmap.c

@@ -5383,9 +5383,11 @@ xfs_bmap_del_extent_real(
 	 * If we need to, add to list of extents to delete.
 	 */
 	if (!(bflags & XFS_BMAPI_REMAP)) {
+		bool	isrt = xfs_ifork_is_realtime(ip, whichfork);
+
 		if (xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK) {
 			xfs_refcount_decrease_extent(tp, del);
-		} else if (xfs_ifork_is_realtime(ip, whichfork)) {
+		} else if (isrt && !xfs_has_rtgroups(mp)) {
 			error = xfs_bmap_free_rtblocks(tp, del);
 		} else {
 			unsigned int	efi_flags = 0;
@@ -5394,6 +5396,19 @@ xfs_bmap_del_extent_real(
 			    del->br_state == XFS_EXT_UNWRITTEN)
 				efi_flags |= XFS_FREE_EXTENT_SKIP_DISCARD;
 
+			/*
+			 * Historically, we did not use EFIs to free realtime
+			 * extents.  However, when reverse mapping is enabled,
+			 * we must maintain the same order of operations as the
+			 * data device, which is: Remove the file mapping,
+			 * remove the reverse mapping, and then free the
+			 * blocks.  Reflink for realtime volumes requires the
+			 * same sort of ordering.  Both features rely on
+			 * rtgroups, so let's gate rt EFI usage on rtgroups.
+			 */
+			if (isrt)
+				efi_flags |= XFS_FREE_EXTENT_REALTIME;
+
 			error = xfs_free_extent_later(tp, del->br_startblock,
 					del->br_blockcount, NULL,
 					XFS_AG_RESV_NONE, efi_flags);