xfs: Introduce a new transaction for shrinking fs data section

index 9eaea5a..9bf3ed6 100644
@@ -41,6 +41,7 @@ typedef struct xfs_trans_reservations {
 	uint	tr_growrtzero;	/* grow realtime zeroing */
 	uint	tr_growrtfree;	/* grow realtime freeing */
 	uint	tr_setagstate;	/* set a.g. state trans */
+	uint	tr_shrinkdata;	/* fs data section shrink trans */
 } xfs_trans_reservations_t;
 
 #ifndef __KERNEL__

index 5a5c4d8..d7346da 100644
@@ -542,6 +542,21 @@ xfs_calc_set_agstate_reservation(
 }
 
 /*
+ * Shrinking the data section of the filesystem.
+ *	superblock
+ *	agi and agf
+ *	allocation btrees
+ */
+STATIC uint
+xfs_calc_shrinkdata_reservation(
+	struct xfs_mount	*mp)
+{
+	return mp->m_sb.sb_sectsize * 3 +
+		XFS_ALLOCFREE_LOG_RES(mp, 1) +
+		128 * (3 + XFS_ALLOCFREE_LOG_COUNT(mp, 1));
+}
+
+/*
  * Initialize the precomputed transaction reservation values
  * in the mount structure.
  */

@@ -573,6 +588,7 @@ xfs_trans_init(
 	resp->tr_growrtzero = xfs_calc_growrtzero_reservation(mp);
 	resp->tr_growrtfree = xfs_calc_growrtfree_reservation(mp);
 	resp->tr_setagstate = xfs_calc_set_agstate_reservation(mp);
+	resp->tr_shrinkdata = xfs_calc_shrinkdata_reservation(mp);
 }
 
 /*

index 33aafda..6dc1fe8 100644
@@ -109,7 +109,8 @@ typedef struct xfs_trans_header {
 #define	XFS_TRANS_CHECKPOINT		42
 #define XFS_TRANS_SET_AGSTATE		43
 #define XFS_TRANS_SWAPINO		44
-#define	XFS_TRANS_TYPE_MAX		44
+#define XFS_TRANS_SHRINKFS		45
+#define	XFS_TRANS_TYPE_MAX		45
 /* new transaction types need to be reflected in xfs_logprint(8) */
 
 #define XFS_TRANS_TYPES \

@@ -156,7 +157,8 @@ typedef struct xfs_trans_header {
 	{ XFS_TRANS_DUMMY2,		"DUMMY2" }, \
 	{ XLOG_UNMOUNT_REC_TYPE,	"UNMOUNT" }, \
 	{ XFS_TRANS_SET_AGSTATE,	"SET_AGSTATE" }, \
-	{ XFS_TRANS_SWAPINO,		"SWAPINO" }
+	{ XFS_TRANS_SWAPINO,		"SWAPINO" }, \
+	{ XFS_TRANS_SHRINKFS,		"SHRINKFS" }
 
 /*
  * This structure is used to track log items associated with

@@ -267,6 +269,7 @@ struct xfs_log_item_desc {
 #define	XFS_ATTRRM_LOG_RES(mp)	((mp)->m_reservations.tr_attrrm)
 #define	XFS_CLEAR_AGI_BUCKET_LOG_RES(mp)  ((mp)->m_reservations.tr_clearagi)
 #define XFS_SETAGSTATE_LOG_RES(mp) ((mp)->m_reservations.tr_setagstate)
+#define XFS_SHRINKDATA_LOG_RES(mp) ((mp)->m_reservations.tr_shrinkdata)
 
 /*
  * Various log count values.

index 7d2c920..103e442 100644
@@ -82,5 +82,7 @@
 	(XFS_DIRREMOVE_SPACE_RES(mp) + XFS_DIRENTER_SPACE_RES(mp,nl))
 #define	XFS_SYMLINK_SPACE_RES(mp,nl,b)	\
 	(XFS_IALLOC_SPACE_RES(mp) + XFS_DIRENTER_SPACE_RES(mp,nl) + (b))
+#define	XFS_SHRINKFS_SPACE_RES(mp)	\
+	(2 * XFS_AG_MAXLEVELS(mp))
 
 #endif	/* __XFS_TRANS_SPACE_H__ */