xfs: move busy extent handling to it's own file

To make it easier to handle userspace code merges, move all the busy
extent handling out of the allocation code and into it's own file.
The userspace code does not need the busy extent code, so this
simplifies the merging of the kernel code into the userspace
xfsprogs library.

Because the busy extent code has been almost completely rewritten
over the past couple of years, also update the copyright on this new
file to include the authors that made all those changes.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/Makefile

@@ -33,6 +33,7 @@ xfs-y				+= xfs_aops.o \
 				   xfs_discard.o \
 				   xfs_error.o \
 				   xfs_export.o \
+				   xfs_extent_busy.o \
 				   xfs_file.o \
 				   xfs_filestream.o \
 				   xfs_fsops.o \

fs/xfs/xfs_ag.h

@@ -174,24 +174,6 @@ typedef struct xfs_agfl {
 	__be32		agfl_bno[1];	/* actually XFS_AGFL_SIZE(mp) */
 } xfs_agfl_t;
 
-/*
- * Busy block/extent entry.  Indexed by a rbtree in perag to mark blocks that
- * have been freed but whose transactions aren't committed to disk yet.
- *
- * Note that we use the transaction ID to record the transaction, not the
- * transaction structure itself. See xfs_alloc_busy_insert() for details.
- */
-struct xfs_busy_extent {
-	struct rb_node	rb_node;	/* ag by-bno indexed search tree */
-	struct list_head list;		/* transaction busy extent list */
-	xfs_agnumber_t	agno;
-	xfs_agblock_t	bno;
-	xfs_extlen_t	length;
-	unsigned int	flags;
-#define XFS_ALLOC_BUSY_DISCARDED	0x01	/* undergoing a discard op. */
-#define XFS_ALLOC_BUSY_SKIP_DISCARD	0x02	/* do not discard */
-};
-
 /*
  * Per-ag incore structure, copies of information in agf and agi,
  * to improve the performance of allocation group selection.