xfsprogs: introduce the free inode btree

index f38b220..d7ebea7 100644
@@ -58,7 +58,8 @@ struct xfs_mount;
 		 ((index) - 1) * sizeof(xfs_inobt_ptr_t)))
 
 extern struct xfs_btree_cur *xfs_inobt_init_cursor(struct xfs_mount *,
-		struct xfs_trans *, struct xfs_buf *, xfs_agnumber_t);
+		struct xfs_trans *, struct xfs_buf *, xfs_agnumber_t,
+		xfs_btnum_t);
 extern int xfs_inobt_maxrecs(struct xfs_mount *, int, int);
 
 #endif	/* __XFS_IALLOC_BTREE_H__ */

index c19d84a..d4a4511 100644
@@ -432,7 +432,7 @@ xfs_ialloc_ag_alloc(
 	/*
 	 * Insert records describing the new inode chunk into the btree.
 	 */
-	cur = xfs_inobt_init_cursor(args.mp, tp, agbp, agno);
+	cur = xfs_inobt_init_cursor(args.mp, tp, agbp, agno, XFS_BTNUM_INO);
 	for (thisino = newino;
 	     thisino < newino + newlen;
 	     thisino += XFS_INODES_PER_CHUNK) {

@@ -678,7 +678,7 @@ xfs_dialloc_ag(
 	ASSERT(pag->pagi_freecount > 0);
 
  restart_pagno:
-	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno);
+	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_INO);
 	/*
 	 * If pagino is 0 (this is the root inode allocation) use newino.
 	 * This must work because we've just allocated some.

@@ -1140,7 +1140,7 @@ xfs_difree(
 	/*
 	 * Initialize the cursor.
 	 */
-	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno);
+	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_INO);
 
 	error = xfs_check_agi_freecount(cur, agi);
 	if (error)

@@ -1271,7 +1271,7 @@ xfs_imap_lookup(
 	 * we have a record, we need to ensure it contains the inode number
 	 * we are looking up.
 	 */
-	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno);
+	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_INO);
 	error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_LE, &i);
 	if (!error) {
 		if (i)

index 0a29d73..2027bc6 100644
@@ -30,7 +30,8 @@ xfs_inobt_dup_cursor(
 	struct xfs_btree_cur	*cur)
 {
 	return xfs_inobt_init_cursor(cur->bc_mp, cur->bc_tp,
-			cur->bc_private.a.agbp, cur->bc_private.a.agno);
+			cur->bc_private.a.agbp, cur->bc_private.a.agno,
+			cur->bc_btnum);
 }
 
 STATIC void

@@ -379,7 +380,8 @@ xfs_inobt_init_cursor(
 	struct xfs_mount	*mp,		/* file system mount point */
 	struct xfs_trans	*tp,		/* transaction pointer */
 	struct xfs_buf		*agbp,		/* buffer for agi structure */
-	xfs_agnumber_t		agno)		/* allocation group number */
+	xfs_agnumber_t		agno,		/* allocation group number */
+	xfs_btnum_t		btnum)		/* ialloc or free ino btree */
 {
 	struct xfs_agi		*agi = XFS_BUF_TO_AGI(agbp);
 	struct xfs_btree_cur	*cur;

@@ -389,7 +391,7 @@ xfs_inobt_init_cursor(
 	cur->bc_tp = tp;
 	cur->bc_mp = mp;
 	cur->bc_nlevels = be32_to_cpu(agi->agi_level);
-	cur->bc_btnum = XFS_BTNUM_INO;
+	cur->bc_btnum = btnum;
 	cur->bc_blocklog = mp->m_sb.sb_blocklog;
 
 	cur->bc_ops = &xfs_inobt_ops;

index f7b2fe7..7f53a85 100644
@@ -587,6 +587,7 @@ xfs_sb_has_compat_feature(
 	return (sbp->sb_features_compat & feature) != 0;
 }
 
+#define XFS_SB_FEAT_RO_COMPAT_FINOBT   (1 << 0)		/* free inode btree */
 #define XFS_SB_FEAT_RO_COMPAT_ALL 0
 #define XFS_SB_FEAT_RO_COMPAT_UNKNOWN	~XFS_SB_FEAT_RO_COMPAT_ALL
 static inline bool

@@ -641,6 +642,12 @@ static inline int xfs_sb_version_hasftype(struct xfs_sb *sbp)
 		 (sbp->sb_features2 & XFS_SB_VERSION2_FTYPE));
 }
 
+static inline int xfs_sb_version_hasfinobt(xfs_sb_t *sbp)
+{
+	return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) &&
+		(sbp->sb_features_ro_compat & XFS_SB_FEAT_RO_COMPAT_FINOBT);
+}
+
 /*
  * end of superblock version macros
  */

index 0fdd410..2531658 100644
@@ -166,24 +166,30 @@ typedef struct xfs_agi {
 	__be32		agi_pad32;
 	__be64		agi_lsn;	/* last write sequence */
 
+	__be32		agi_free_root; /* root of the free inode btree */
+	__be32		agi_free_level;/* levels in free inode btree */
+
 	/* structure must be padded to 64 bit alignment */
 } xfs_agi_t;
 
 #define XFS_AGI_CRC_OFF		offsetof(struct xfs_agi, agi_crc)
 
-#define	XFS_AGI_MAGICNUM	0x00000001
-#define	XFS_AGI_VERSIONNUM	0x00000002
-#define	XFS_AGI_SEQNO		0x00000004
-#define	XFS_AGI_LENGTH		0x00000008
-#define	XFS_AGI_COUNT		0x00000010
-#define	XFS_AGI_ROOT		0x00000020
-#define	XFS_AGI_LEVEL		0x00000040
-#define	XFS_AGI_FREECOUNT	0x00000080
-#define	XFS_AGI_NEWINO		0x00000100
-#define	XFS_AGI_DIRINO		0x00000200
-#define	XFS_AGI_UNLINKED	0x00000400
-#define	XFS_AGI_NUM_BITS	11
-#define	XFS_AGI_ALL_BITS	((1 << XFS_AGI_NUM_BITS) - 1)
+#define	XFS_AGI_MAGICNUM	(1 << 0)
+#define	XFS_AGI_VERSIONNUM	(1 << 1)
+#define	XFS_AGI_SEQNO		(1 << 2)
+#define	XFS_AGI_LENGTH		(1 << 3)
+#define	XFS_AGI_COUNT		(1 << 4)
+#define	XFS_AGI_ROOT		(1 << 5)
+#define	XFS_AGI_LEVEL		(1 << 6)
+#define	XFS_AGI_FREECOUNT	(1 << 7)
+#define	XFS_AGI_NEWINO		(1 << 8)
+#define	XFS_AGI_DIRINO		(1 << 9)
+#define	XFS_AGI_UNLINKED	(1 << 10)
+#define	XFS_AGI_NUM_BITS_R1	11	/* end of the 1st agi logging region */
+#define	XFS_AGI_ALL_BITS_R1	((1 << XFS_AGI_NUM_BITS_R1) - 1)
+#define	XFS_AGI_FREE_ROOT	(1 << 11)
+#define	XFS_AGI_FREE_LEVEL	(1 << 12)
+#define	XFS_AGI_NUM_BITS_R2	13
 
 /* disk block (xfs_daddr_t) in the AG */
 #define XFS_AGI_DADDR(mp)	((xfs_daddr_t)(2 << (mp)->m_sectbb_log))

index 6afe0b2..2590d40 100644
@@ -37,6 +37,7 @@ extern kmem_zone_t	*xfs_btree_cur_zone;
 #define	XFS_BTNUM_CNT	((xfs_btnum_t)XFS_BTNUM_CNTi)
 #define	XFS_BTNUM_BMAP	((xfs_btnum_t)XFS_BTNUM_BMAPi)
 #define	XFS_BTNUM_INO	((xfs_btnum_t)XFS_BTNUM_INOi)
+#define	XFS_BTNUM_FINO	((xfs_btnum_t)XFS_BTNUM_FINOi)
 
 /*
  * For logging record fields.

@@ -67,6 +68,7 @@ do {    \
 	case XFS_BTNUM_CNT: __XFS_BTREE_STATS_INC(abtc, stat); break;	\
 	case XFS_BTNUM_BMAP: __XFS_BTREE_STATS_INC(bmbt, stat); break;	\
 	case XFS_BTNUM_INO: __XFS_BTREE_STATS_INC(ibt, stat); break;	\
+	case XFS_BTNUM_FINO: __XFS_BTREE_STATS_INC(fibt, stat); break;	\
 	case XFS_BTNUM_MAX: ASSERT(0); /* fucking gcc */ ; break;	\
 	}       \
 } while (0)

@@ -80,6 +82,7 @@ do {    \
 	case XFS_BTNUM_CNT: __XFS_BTREE_STATS_ADD(abtc, stat, val); break; \
 	case XFS_BTNUM_BMAP: __XFS_BTREE_STATS_ADD(bmbt, stat, val); break; \
 	case XFS_BTNUM_INO: __XFS_BTREE_STATS_ADD(ibt, stat, val); break; \
+	case XFS_BTNUM_FINO: __XFS_BTREE_STATS_ADD(fibt, stat, val); break; \
 	case XFS_BTNUM_MAX: ASSERT(0); /* fucking gcc */ ; break;	\
 	}       \
 } while (0)

index 77f6b8b..758052f 100644
@@ -202,6 +202,8 @@ typedef __be32 xfs_alloc_ptr_t;
  */
 #define	XFS_IBT_MAGIC		0x49414254	/* 'IABT' */
 #define	XFS_IBT_CRC_MAGIC	0x49414233	/* 'IAB3' */
+#define	XFS_FIBT_MAGIC		0x46494254	/* 'FIBT' */
+#define	XFS_FIBT_CRC_MAGIC	0x46494233	/* 'FIB3' */
 
 typedef	__uint64_t	xfs_inofree_t;
 #define	XFS_INODES_PER_CHUNK		(NBBY * sizeof(xfs_inofree_t))

@@ -244,7 +246,17 @@ typedef __be32 xfs_inobt_ptr_t;
  * block numbers in the AG.
  */
 #define	XFS_IBT_BLOCK(mp)		((xfs_agblock_t)(XFS_CNT_BLOCK(mp) + 1))
-#define	XFS_PREALLOC_BLOCKS(mp)		((xfs_agblock_t)(XFS_IBT_BLOCK(mp) + 1))
+#define	XFS_FIBT_BLOCK(mp)		((xfs_agblock_t)(XFS_IBT_BLOCK(mp) + 1))
+
+/*
+ * The first data block of an AG depends on whether the filesystem was formatted
+ * with the finobt feature. If so, account for the finobt reserved root btree
+ * block.
+ */
+#define XFS_PREALLOC_BLOCKS(mp) \
+	(xfs_sb_version_hasfinobt(&((mp)->m_sb)) ? \
+	 XFS_FIBT_BLOCK(mp) + 1 : \
+	 XFS_IBT_BLOCK(mp) + 1)
 
 
 

index 82bbc34..65c6e66 100644
@@ -134,7 +134,7 @@ typedef enum {
 
 typedef enum {
 	XFS_BTNUM_BNOi, XFS_BTNUM_CNTi, XFS_BTNUM_BMAPi, XFS_BTNUM_INOi,
-	XFS_BTNUM_MAX
+	XFS_BTNUM_FINOi, XFS_BTNUM_MAX
 } xfs_btnum_t;
 
 struct xfs_name {

index 9be4abd..cc823f5 100644
@@ -27,9 +27,10 @@ kmem_zone_t	*xfs_btree_cur_zone;
  * Btree magic numbers.
  */
 static const __uint32_t xfs_magics[2][XFS_BTNUM_MAX] = {
-	{ XFS_ABTB_MAGIC, XFS_ABTC_MAGIC, XFS_BMAP_MAGIC, XFS_IBT_MAGIC },
+	{ XFS_ABTB_MAGIC, XFS_ABTC_MAGIC, XFS_BMAP_MAGIC, XFS_IBT_MAGIC,
+	  XFS_FIBT_MAGIC },
 	{ XFS_ABTB_CRC_MAGIC, XFS_ABTC_CRC_MAGIC,
-	  XFS_BMAP_CRC_MAGIC, XFS_IBT_CRC_MAGIC }
+	  XFS_BMAP_CRC_MAGIC, XFS_IBT_CRC_MAGIC, XFS_FIBT_CRC_MAGIC }
 };
 #define xfs_btree_magic(cur) \
 	xfs_magics[!!((cur)->bc_flags & XFS_BTREE_CRC_BLOCKS)][cur->bc_btnum]

@@ -1099,6 +1100,7 @@ xfs_btree_set_refs(
 		xfs_buf_set_ref(bp, XFS_ALLOC_BTREE_REF);
 		break;
 	case XFS_BTNUM_INO:
+	case XFS_BTNUM_FINO:
 		xfs_buf_set_ref(bp, XFS_INO_BTREE_REF);
 		break;
 	case XFS_BTNUM_BMAP:

index d4a4511..4a7746a 100644
@@ -1482,6 +1482,8 @@ xfs_ialloc_log_agi(
 		offsetof(xfs_agi_t, agi_newino),
 		offsetof(xfs_agi_t, agi_dirino),
 		offsetof(xfs_agi_t, agi_unlinked),
+		offsetof(xfs_agi_t, agi_free_root),
+		offsetof(xfs_agi_t, agi_free_level),
 		sizeof(xfs_agi_t)
 	};
 #ifdef DEBUG

@@ -1491,14 +1493,39 @@ xfs_ialloc_log_agi(
 	ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
 #endif
 	/*
-	 * Compute byte offsets for the first and last fields.
+	 * The growth of the agi buffer over time now requires that we interpret
+	 * the buffer as two logical regions delineated at the end of the unlinked
+	 * list. This is due to the size of the hash table and its location in the
+	 * middle of the agi.
+	 *
+	 * For example, a request to log a field before agi_unlinked and a field
+	 * after agi_unlinked could cause us to log the entire hash table and use
+	 * an excessive amount of log space. To avoid this behavior, log the
+	 * region up through agi_unlinked in one call and the region after
+	 * agi_unlinked through the end of the structure in another.
 	 */
-	xfs_btree_offsets(fields, offsets, XFS_AGI_NUM_BITS, &first, &last);
+	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_AGI_BUF);
+
 	/*
-	 * Log the allocation group inode header buffer.
+	 * Compute byte offsets for the first and last fields in the first
+	 * region and log agi buffer. This only logs up through agi_unlinked.
 	 */
-	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_AGI_BUF);
-	xfs_trans_log_buf(tp, bp, first, last);
+	if (fields & XFS_AGI_ALL_BITS_R1) {
+		xfs_btree_offsets(fields, offsets, XFS_AGI_NUM_BITS_R1,
+				  &first, &last);
+		xfs_trans_log_buf(tp, bp, first, last);
+	}
+
+	/*
+	 * Mask off the bits in the first region and calculate the first and last
+	 * field offsets for any bits in the second region.
+	 */
+	fields &= ~XFS_AGI_ALL_BITS_R1;
+	if (fields) {
+		xfs_btree_offsets(fields, offsets, XFS_AGI_NUM_BITS_R2,
+				  &first, &last);
+		xfs_trans_log_buf(tp, bp, first, last);
+	}
 }
 
 #ifdef DEBUG

99 lines not on this page · raw message

index 7d2c920..a7d1721 100644
@@ -47,7 +47,9 @@
 #define	XFS_DIRREMOVE_SPACE_RES(mp)	\
 	XFS_DAREMOVE_SPACE_RES(mp, XFS_DATA_FORK)
 #define	XFS_IALLOC_SPACE_RES(mp)	\
-	(XFS_IALLOC_BLOCKS(mp) + (mp)->m_in_maxlevels - 1)
+	(XFS_IALLOC_BLOCKS(mp) + \
+	 (xfs_sb_version_hasfinobt(&mp->m_sb) ? 2 : 1 * \
+	  ((mp)->m_in_maxlevels - 1)))
 
 /*
  * Space reservation values for various transactions.

@@ -82,5 +84,8 @@
 	(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_IFREE_SPACE_RES(mp)		\
+	(xfs_sb_version_hasfinobt(&mp->m_sb) ? (mp)->m_in_maxlevels : 0)
+
 
 #endif	/* __XFS_TRANS_SPACE_H__ */

101 lines not on this page · raw message

index 4a7746a..c5759aa 100644
@@ -88,6 +88,66 @@ xfs_inobt_get_rec(
 }
 
 /*
+ * Insert a single inobt record. Cursor must already point to desired location.
+ */
+STATIC int
+xfs_inobt_insert_rec(
+	struct xfs_btree_cur	*cur,
+	__int32_t		freecount,
+	xfs_inofree_t		free,
+	int			*stat)
+{
+	cur->bc_rec.i.ir_freecount = freecount;
+	cur->bc_rec.i.ir_free = free;
+	return xfs_btree_insert(cur, stat);
+}
+
+/*
+ * Insert records describing a newly allocated inode chunk into the inobt.
+ */
+STATIC int
+xfs_inobt_insert(
+	struct xfs_mount	*mp,
+	struct xfs_trans	*tp,
+	struct xfs_buf		*agbp,
+	xfs_agino_t		newino,
+	xfs_agino_t		newlen,
+	xfs_btnum_t		btnum)
+{
+	struct xfs_btree_cur	*cur;
+	struct xfs_agi		*agi = XFS_BUF_TO_AGI(agbp);
+	xfs_agnumber_t		agno = be32_to_cpu(agi->agi_seqno);
+	xfs_agino_t		thisino;
+	int			i;
+	int			error;
+
+	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, btnum);
+
+	for (thisino = newino;
+	     thisino < newino + newlen;
+	     thisino += XFS_INODES_PER_CHUNK) {
+		error = xfs_inobt_lookup(cur, thisino, XFS_LOOKUP_EQ, &i);
+		if (error) {
+			xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+			return error;
+		}
+		ASSERT(i == 0);
+
+		error = xfs_inobt_insert_rec(cur, XFS_INODES_PER_CHUNK,
+					     XFS_INOBT_ALL_FREE, &i);
+		if (error) {
+			xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+			return error;
+		}
+		ASSERT(i == 1);
+	}
+
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+
+	return 0;
+}
+
+/*
  * Verify that the number of free inodes in the AGI is correct.
  */
 #ifdef DEBUG

@@ -286,13 +346,10 @@ xfs_ialloc_ag_alloc(
 {
 	xfs_agi_t	*agi;		/* allocation group header */
 	xfs_alloc_arg_t	args;		/* allocation argument structure */
-	xfs_btree_cur_t	*cur;		/* inode btree cursor */
 	xfs_agnumber_t	agno;
 	int		error;
-	int		i;
 	xfs_agino_t	newino;		/* new first inode's number */
 	xfs_agino_t	newlen;		/* new number of inodes */
-	xfs_agino_t	thisino;	/* current inode number, for loop */
 	int		isaligned = 0;	/* inode allocation at stripe unit */
 					/* boundary */
 	struct xfs_perag *pag;

@@ -430,29 +487,19 @@ xfs_ialloc_ag_alloc(
 	agi->agi_newino = cpu_to_be32(newino);
 
 	/*
-	 * Insert records describing the new inode chunk into the btree.
+	 * Insert records describing the new inode chunk into the btrees.
 	 */
-	cur = xfs_inobt_init_cursor(args.mp, tp, agbp, agno, XFS_BTNUM_INO);
-	for (thisino = newino;
-	     thisino < newino + newlen;
-	     thisino += XFS_INODES_PER_CHUNK) {
-		cur->bc_rec.i.ir_startino = thisino;
-		cur->bc_rec.i.ir_freecount = XFS_INODES_PER_CHUNK;
-		cur->bc_rec.i.ir_free = XFS_INOBT_ALL_FREE;
-		error = xfs_btree_lookup(cur, XFS_LOOKUP_EQ, &i);
-		if (error) {
-			xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
-			return error;
-		}
-		ASSERT(i == 0);
-		error = xfs_btree_insert(cur, &i);
-		if (error) {
-			xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+	error = xfs_inobt_insert(args.mp, tp, agbp, newino, newlen,
+				 XFS_BTNUM_INO);
+	if (error)
+		return error;
+
+	if (xfs_sb_version_hasfinobt(&args.mp->m_sb)) {
+		error = xfs_inobt_insert(args.mp, tp, agbp, newino, newlen,
+					 XFS_BTNUM_FINO);
+		if (error)
 			return error;
-		}
-		ASSERT(i == 1);
 	}
-	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
 	/*
 	 * Log allocation group header fields
 	 */

index c5759aa..462340b 100644
@@ -699,7 +699,7 @@ xfs_ialloc_get_rec(
  * available.
  */
 STATIC int
-xfs_dialloc_ag(
+xfs_dialloc_ag_slow(
 	struct xfs_trans	*tp,
 	struct xfs_buf		*agbp,
 	xfs_ino_t		parent,

@@ -957,6 +957,215 @@ error0:
 	return error;
 }
 
+STATIC int
+xfs_dialloc_ag(
+	struct xfs_trans	*tp,
+	struct xfs_buf		*agbp,
+	xfs_ino_t		parent,
+	xfs_ino_t		*inop)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_agi			*agi = XFS_BUF_TO_AGI(agbp);
+	xfs_agnumber_t			agno = be32_to_cpu(agi->agi_seqno);
+	xfs_agnumber_t			pagno = XFS_INO_TO_AGNO(mp, parent);
+	xfs_agino_t			pagino = XFS_INO_TO_AGINO(mp, parent);
+	struct xfs_perag		*pag;
+	struct xfs_btree_cur		*cur;
+	struct xfs_btree_cur		*tcur;
+	struct xfs_inobt_rec_incore	rec;
+	struct xfs_inobt_rec_incore	trec;
+	xfs_ino_t			ino;
+	int				error;
+	int				offset;
+	int				i, j;
+
+	if (!xfs_sb_version_hasfinobt(&mp->m_sb))
+		return xfs_dialloc_ag_slow(tp, agbp, parent, inop);
+
+	pag = xfs_perag_get(mp, agno);
+
+	/*
+	 * If pagino is 0 (this is the root inode allocation) use newino.
+	 * This must work because we've just allocated some.
+	 */
+	if (!pagino)
+		pagino = be32_to_cpu(agi->agi_newino);
+
+	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_FINO);
+
+	error = xfs_check_agi_freecount(cur, agi);
+	if (error)
+		goto error_cur;
+
+	if (agno == pagno) {
+		/*
+		 * We're in the same AG as the parent inode so allocate the
+		 * closest inode to the parent.
+		 */
+		error = xfs_inobt_lookup(cur, pagino, XFS_LOOKUP_LE, &i);
+		if (error)
+			goto error_cur;
+		if (i == 1) {
+			error = xfs_inobt_get_rec(cur, &rec, &i);
+			if (error)
+				goto error_cur;
+			XFS_WANT_CORRUPTED_GOTO(i == 1, error_cur);
+
+			/*
+			 * See if we've landed in the parent inode record. The
+			 * finobt only tracks chunks with at least one free
+			 * inode, so record existence is enough.
+			 */
+			if (pagino >= rec.ir_startino &&
+			    pagino < (rec.ir_startino + XFS_INODES_PER_CHUNK))
+				goto alloc_inode;
+		}
+
+		error = xfs_btree_dup_cursor(cur, &tcur);
+		if (error) 
+			goto error_cur;
+
+		error = xfs_inobt_lookup(tcur, pagino, XFS_LOOKUP_GE, &j);
+		if (error)
+			goto error_tcur;
+		if (j == 1) {
+			error = xfs_inobt_get_rec(tcur, &trec, &j);
+			if (error)
+				goto error_tcur;
+			XFS_WANT_CORRUPTED_GOTO(j == 1, error_tcur);
+		}
+
+		if (i == 1 && j == 1) {
+			if ((pagino - rec.ir_startino + XFS_INODES_PER_CHUNK - 1) >
+			    (trec.ir_startino - pagino)) {
+				rec = trec;
+				xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+				cur = tcur;
+			} else {
+				xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
+			}
+		} else if (j == 1) {
+			rec = trec;
+			xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+			cur = tcur;
+		} else {
+			xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
+		}
+	} else {
+		/*
+		 * Different AG from the parent inode. Check the record for the
+		 * most recently allocated inode.
+		 */
+		if (agi->agi_newino != cpu_to_be32(NULLAGINO)) {
+			error = xfs_inobt_lookup(cur, agi->agi_newino,
+						 XFS_LOOKUP_EQ, &i);
+			if (error)
+				goto error_cur;
+			if (i == 1) {
+				error = xfs_inobt_get_rec(cur, &rec, &i);
+				if (error)
+					goto error_cur;
+				XFS_WANT_CORRUPTED_GOTO(i == 1, error_cur);
+				goto alloc_inode;
+			}
+		}
+
+		/*
+		 * Allocate the first inode available in the AG.
+		 */
+		error = xfs_inobt_lookup(cur, 0, XFS_LOOKUP_GE, &i);
+		if (error)
+			goto error_cur;
+		XFS_WANT_CORRUPTED_GOTO(i == 1, error_cur);
+
+		error = xfs_inobt_get_rec(cur, &rec, &i);
+		if (error)
+			goto error_cur;
+		XFS_WANT_CORRUPTED_GOTO(i == 1, error_cur);
+	}
+
+alloc_inode:
+	offset = xfs_lowbit64(rec.ir_free);
+	ASSERT(offset >= 0);
+	ASSERT(offset < XFS_INODES_PER_CHUNK);
+	ASSERT((XFS_AGINO_TO_OFFSET(mp, rec.ir_startino) %
+				   XFS_INODES_PER_CHUNK) == 0);
+	ino = XFS_AGINO_TO_INO(mp, agno, rec.ir_startino + offset);
+
+	/*
+	 * Modify or remove the finobt record.
+	 */
+	rec.ir_free &= ~XFS_INOBT_MASK(offset);
+	rec.ir_freecount--;
+	if (rec.ir_freecount) 
+		error = xfs_inobt_update(cur, &rec);
+	else
+		error = xfs_btree_delete(cur, &i);
+	if (error)
+		goto error_cur;
+
+	/*
+	 * Lookup and modify the equivalent record in the inobt.
+	 */
+	tcur = xfs_inobt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_INO);
+
+	error = xfs_check_agi_freecount(tcur, agi);
+	if (error)
+		goto error_tcur;
+
+	error = xfs_inobt_lookup(tcur, rec.ir_startino, XFS_LOOKUP_EQ, &i);
+	if (error)
+		goto error_tcur;
+	XFS_WANT_CORRUPTED_GOTO(i == 1, error_tcur);
+
+	error = xfs_inobt_get_rec(tcur, &trec, &i);
+	if (error)
+		goto error_tcur;
+	XFS_WANT_CORRUPTED_GOTO(i == 1, error_tcur);
+	ASSERT((XFS_AGINO_TO_OFFSET(mp, trec.ir_startino) %
+				   XFS_INODES_PER_CHUNK) == 0);
+
+	trec.ir_free &= ~XFS_INOBT_MASK(offset);
+	trec.ir_freecount--;
+
+	XFS_WANT_CORRUPTED_GOTO((rec.ir_free == trec.ir_free) &&
+				(rec.ir_freecount == trec.ir_freecount),
+				error_tcur);
+
+	error = xfs_inobt_update(tcur, &trec);
+	if (error)
+		goto error_tcur;
+
+	/*
+	 * Update the perag and superblock.
+	 */
+	be32_add_cpu(&agi->agi_freecount, -1);
+	xfs_ialloc_log_agi(tp, agbp, XFS_AGI_FREECOUNT);
+	pag->pagi_freecount--;
+
+	xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, -1);
+
+	error = xfs_check_agi_freecount(tcur, agi);
+	if (error)
+		goto error_tcur;
+	error = xfs_check_agi_freecount(cur, agi);
+	if (error)
+		goto error_tcur;
+
+	xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+	xfs_perag_put(pag);
+	*inop = ino;
+	return 0;
+
+error_tcur:
+	xfs_btree_del_cursor(tcur, XFS_BTREE_ERROR);
+error_cur:
+	xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+	xfs_perag_put(pag);
+	return error;
+}
+
 /*
  * Allocate an inode on disk.
  *

index 462340b..f0d6397 100644
@@ -1325,74 +1325,30 @@ out_error:
 	return XFS_ERROR(error);
 }
 
-/*
- * Free disk inode.  Carefully avoids touching the incore inode, all
- * manipulations incore are the caller's responsibility.
- * The on-disk inode is not changed by this operation, only the
- * btree (free inode mask) is changed.
- */
-int
-xfs_difree(
-	xfs_trans_t	*tp,		/* transaction pointer */
-	xfs_ino_t	inode,		/* inode to be freed */
-	xfs_bmap_free_t	*flist,		/* extents to free */
-	int		*delete,	/* set if inode cluster was deleted */
-	xfs_ino_t	*first_ino)	/* first inode in deleted cluster */
+STATIC int
+xfs_difree_inobt(
+	struct xfs_mount		*mp,
+	struct xfs_trans		*tp,
+	struct xfs_buf			*agbp,
+	xfs_agino_t			agino,
+	struct xfs_bmap_free		*flist,
+	int				*delete,
+	xfs_ino_t			*first_ino,
+	struct xfs_inobt_rec_incore	*orec)
 {
-	/* REFERENCED */
-	xfs_agblock_t	agbno;	/* block number containing inode */
-	xfs_buf_t	*agbp;	/* buffer containing allocation group header */
-	xfs_agino_t	agino;	/* inode number relative to allocation group */
-	xfs_agnumber_t	agno;	/* allocation group number */
-	xfs_agi_t	*agi;	/* allocation group header */
-	xfs_btree_cur_t	*cur;	/* inode btree cursor */
-	int		error;	/* error return value */
-	int		i;	/* result code */
-	int		ilen;	/* inodes in an inode cluster */
-	xfs_mount_t	*mp;	/* mount structure for filesystem */
-	int		off;	/* offset of inode in inode chunk */
-	xfs_inobt_rec_incore_t rec;	/* btree record */
-	struct xfs_perag *pag;
-
-	mp = tp->t_mountp;
+	struct xfs_agi			*agi = XFS_BUF_TO_AGI(agbp);
+	xfs_agnumber_t			agno = be32_to_cpu(agi->agi_seqno);
+	struct xfs_perag		*pag;
+	struct xfs_btree_cur		*cur;
+	struct xfs_inobt_rec_incore	rec;
+	int				ilen;
+	int				error;
+	int				i;
+	int				off;
 
-	/*
-	 * Break up inode number into its components.
-	 */
-	agno = XFS_INO_TO_AGNO(mp, inode);
-	if (agno >= mp->m_sb.sb_agcount)  {
-		xfs_warn(mp, "%s: agno >= mp->m_sb.sb_agcount (%d >= %d).",
-			__func__, agno, mp->m_sb.sb_agcount);
-		ASSERT(0);
-		return XFS_ERROR(EINVAL);
-	}
-	agino = XFS_INO_TO_AGINO(mp, inode);
-	if (inode != XFS_AGINO_TO_INO(mp, agno, agino))  {
-		xfs_warn(mp, "%s: inode != XFS_AGINO_TO_INO() (%llu != %llu).",
-			__func__, (unsigned long long)inode,
-			(unsigned long long)XFS_AGINO_TO_INO(mp, agno, agino));
-		ASSERT(0);
-		return XFS_ERROR(EINVAL);
-	}
-	agbno = XFS_AGINO_TO_AGBNO(mp, agino);
-	if (agbno >= mp->m_sb.sb_agblocks)  {
-		xfs_warn(mp, "%s: agbno >= mp->m_sb.sb_agblocks (%d >= %d).",
-			__func__, agbno, mp->m_sb.sb_agblocks);
-		ASSERT(0);
-		return XFS_ERROR(EINVAL);
-	}
-	/*
-	 * Get the allocation group header.
-	 */
-	error = xfs_ialloc_read_agi(mp, tp, agno, &agbp);
-	if (error) {
-		xfs_warn(mp, "%s: xfs_ialloc_read_agi() returned error %d.",
-			__func__, error);
-		return error;
-	}
-	agi = XFS_BUF_TO_AGI(agbp);
 	ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
-	ASSERT(agbno < be32_to_cpu(agi->agi_length));
+	ASSERT(XFS_AGINO_TO_AGBNO(mp, agino) < be32_to_cpu(agi->agi_length));
+
 	/*
 	 * Initialize the cursor.
 	 */

@@ -1488,6 +1444,7 @@ xfs_difree(
 	if (error)
 		goto error0;
 
+	*orec = rec;
 	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
 	return 0;
 

@@ -1496,6 +1453,80 @@ error0:
 	return error;
 }
 
+/*
+ * Free disk inode.  Carefully avoids touching the incore inode, all
+ * manipulations incore are the caller's responsibility.
+ * The on-disk inode is not changed by this operation, only the
+ * btree (free inode mask) is changed.
+ */
+int
+xfs_difree(
+	struct xfs_trans	*tp,		/* transaction pointer */
+	xfs_ino_t		inode,		/* inode to be freed */
+	struct xfs_bmap_free	*flist,		/* extents to free */
+	int			*delete,/* set if inode cluster was deleted */
+	xfs_ino_t		*first_ino)/* first inode in deleted cluster */
+{
+	/* REFERENCED */
+	xfs_agblock_t		agbno;	/* block number containing inode */
+	struct xfs_buf		*agbp;	/* buffer for allocation group header */
+	xfs_agino_t		agino;	/* allocation group inode number */
+	xfs_agnumber_t		agno;	/* allocation group number */
+	int			error;	/* error return value */
+	struct xfs_mount	*mp;	/* mount structure for filesystem */
+	struct xfs_inobt_rec_incore rec;/* btree record */
+
+	mp = tp->t_mountp;
+
+	/*
+	 * Break up inode number into its components.
+	 */
+	agno = XFS_INO_TO_AGNO(mp, inode);
+	if (agno >= mp->m_sb.sb_agcount)  {
+		xfs_warn(mp, "%s: agno >= mp->m_sb.sb_agcount (%d >= %d).",
+			__func__, agno, mp->m_sb.sb_agcount);
+		ASSERT(0);
+		return XFS_ERROR(EINVAL);
+	}
+	agino = XFS_INO_TO_AGINO(mp, inode);
+	if (inode != XFS_AGINO_TO_INO(mp, agno, agino))  {
+		xfs_warn(mp, "%s: inode != XFS_AGINO_TO_INO() (%llu != %llu).",
+			__func__, (unsigned long long)inode,
+			(unsigned long long)XFS_AGINO_TO_INO(mp, agno, agino));
+		ASSERT(0);
+		return XFS_ERROR(EINVAL);
+	}
+	agbno = XFS_AGINO_TO_AGBNO(mp, agino);
+	if (agbno >= mp->m_sb.sb_agblocks)  {
+		xfs_warn(mp, "%s: agbno >= mp->m_sb.sb_agblocks (%d >= %d).",
+			__func__, agbno, mp->m_sb.sb_agblocks);
+		ASSERT(0);
+		return XFS_ERROR(EINVAL);
+	}
+	/*
+	 * Get the allocation group header.
+	 */
+	error = xfs_ialloc_read_agi(mp, tp, agno, &agbp);
+	if (error) {
+		xfs_warn(mp, "%s: xfs_ialloc_read_agi() returned error %d.",
+			__func__, error);
+		return error;
+	}
+
+	/*
+	 * Fix up the inode allocation btree.
+	 */
+	error = xfs_difree_inobt(mp, tp, agbp, agino, flist, delete, first_ino,
+				 &rec);
+	if (error)
+		goto error0;
+
+	return 0;
+
+error0:
+	return error;
+}
+
 STATIC int
 xfs_imap_lookup(
 	struct xfs_mount	*mp,

index f0d6397..21af5b3 100644
@@ -1454,6 +1454,106 @@ error0:
 }
 
 /*
+ * Free an inode in the free inode btree.
+ */
+STATIC int
+xfs_difree_finobt(
+	struct xfs_mount		*mp,
+	struct xfs_trans		*tp,
+	struct xfs_buf			*agbp,
+	xfs_agino_t			agino,
+	struct xfs_inobt_rec_incore	*ibtrec) /* inobt record */
+{
+	struct xfs_agi			*agi = XFS_BUF_TO_AGI(agbp);
+	xfs_agnumber_t			agno = be32_to_cpu(agi->agi_seqno);
+	struct xfs_btree_cur		*cur;
+	struct xfs_inobt_rec_incore	rec;
+	int				offset = agino - ibtrec->ir_startino;
+	int				error;
+	int				i;
+
+	cur = xfs_inobt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_FINO);
+
+	error = xfs_inobt_lookup(cur, ibtrec->ir_startino, XFS_LOOKUP_EQ, &i);
+	if (error)
+		goto error;
+	if (i == 0) {
+		/*
+		 * If the record does not exist in the finobt, we must have just
+		 * freed an inode in a previously fully allocated chunk. If not,
+		 * something is out of sync.
+		 */
+		XFS_WANT_CORRUPTED_GOTO(ibtrec->ir_freecount == 1, error);
+
+		error = xfs_inobt_insert_rec(cur, ibtrec->ir_freecount,
+					     ibtrec->ir_free, &i);
+		if (error)
+			goto error;
+		ASSERT(i == 1);
+
+		goto out;
+	}
+
+	/*
+	 * Read and update the existing record.
+	 */
+	error = xfs_inobt_get_rec(cur, &rec, &i);
+	if (error)
+		goto error;
+	XFS_WANT_CORRUPTED_GOTO(i == 1, error);
+
+	rec.ir_free |= XFS_INOBT_MASK(offset);
+	rec.ir_freecount++;
+
+	XFS_WANT_CORRUPTED_GOTO((rec.ir_free == ibtrec->ir_free) &&
+				(rec.ir_freecount == ibtrec->ir_freecount),
+				error);
+
+	/*
+	 * The content of inobt records should always match between the inobt
+	 * and finobt. The lifecycle of records in the finobt is different from
+	 * the inobt in that the finobt only tracks records with at least one
+	 * free inode. This is to optimize lookup for inode allocation purposes.
+	 * The following checks determine whether to update the existing record or
+	 * remove it entirely.
+	 */
+
+	if (rec.ir_freecount == XFS_IALLOC_INODES(mp) &&
+	    !(mp->m_flags & XFS_MOUNT_IKEEP)) {
+		/*
+		 * If all inodes are free and we're in !ikeep mode, the entire
+		 * inode chunk has been deallocated. Remove the record from the
+		 * finobt.
+		 */
+		error = xfs_btree_delete(cur, &i);
+		if (error)
+			goto error;
+		ASSERT(i == 1);
+	} else {
+		/*
+		 * The existing finobt record was modified and has a combination
+		 * of allocated and free inodes or is completely free and ikeep
+		 * is enabled. Update the record.
+		 */
+		error = xfs_inobt_update(cur, &rec);
+		if (error)
+			goto error;
+	}
+
+out:
+	error = xfs_check_agi_freecount(cur, agi);
+	if (error)
+		goto error;
+
+	xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+	return 0;
+
+error:
+	xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
+	return error;
+}
+
+/*
  * Free disk inode.  Carefully avoids touching the incore inode, all
  * manipulations incore are the caller's responsibility.
  * The on-disk inode is not changed by this operation, only the

@@ -1521,6 +1621,15 @@ xfs_difree(
 	if (error)
 		goto error0;
 
+	/*
+	 * Fix up the free inode btree.
+	 */
+	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
+		error = xfs_difree_finobt(mp, tp, agbp, agino, &rec);
+		if (error)
+			goto error0;
+	}
+
 	return 0;
 
 error0:

index 554fd66..59c40fc 100644
@@ -238,6 +238,7 @@ typedef struct xfs_fsop_resblks {
 #define XFS_FSOP_GEOM_FLAGS_LAZYSB	0x4000	/* lazy superblock counters */
 #define XFS_FSOP_GEOM_FLAGS_V5SB	0x8000	/* version 5 superblock */
 #define XFS_FSOP_GEOM_FLAGS_FTYPE	0x10000	/* inode directory types */
+#define XFS_FSOP_GEOM_FLAGS_FINOBT	0x20000	/* free inode btree */
 
 
 /*

index 7f53a85..950d1ea 100644
@@ -588,7 +588,8 @@ xfs_sb_has_compat_feature(
 }
 
 #define XFS_SB_FEAT_RO_COMPAT_FINOBT   (1 << 0)		/* free inode btree */
-#define XFS_SB_FEAT_RO_COMPAT_ALL 0
+#define XFS_SB_FEAT_RO_COMPAT_ALL \
+		(XFS_SB_FEAT_RO_COMPAT_FINOBT)
 #define XFS_SB_FEAT_RO_COMPAT_UNKNOWN	~XFS_SB_FEAT_RO_COMPAT_ALL
 static inline bool
 xfs_sb_has_ro_compat_feature(

index 37c05a9..188b6b3 100644
@@ -183,6 +183,8 @@ char	*sopts[] = {
 char	*mopts[] = {
 #define	M_CRC		0
 	"crc",
+#define M_FINOBT	1
+	"finobt",
 	NULL
 };
 

@@ -962,6 +964,7 @@ main(
 	struct fs_topology	ft;
 	int			lazy_sb_counters;
 	int			crcs_enabled;
+	int			finobt;
 
 	progname = basename(argv[0]);
 	setlocale(LC_ALL, "");

@@ -995,6 +998,7 @@ main(
 	worst_freelist = 0;
 	lazy_sb_counters = 1;
 	crcs_enabled = 0;
+	finobt = 0;
 	memset(&fsx, 0, sizeof(fsx));
 
 	memset(&xi, 0, sizeof(xi));

@@ -1486,6 +1490,14 @@ _("cannot specify both crc and ftype\n"));
 						usage();
 					}
 					break;
+				case M_FINOBT:
+					if (!value || *value == '\0')
+						reqval('m', mopts, M_CRC);
+					c = atoi(value);
+					if (c < 0 || c > 1)
+						illegal(value, "m finobt");
+					finobt = c;
+					break;
 				default:
 					unknown('m', value);
 				}

@@ -1827,6 +1839,16 @@ _("32 bit Project IDs always enabled on CRC enabled filesytems\n"));
 		}
 	}
 
+	/*
+	 * The kernel doesn't currently support crc=0,finobt=1 filesystems.
+	 * Catch it here, disable finobt and warn the user.
+	 */
+	if (finobt && !crcs_enabled) {
+		fprintf(stderr,
+_("warning: finobt not supported without CRC support, disabled.\n"));
+		finobt = 0;
+	}
+
 	if (nsflag || nlflag) {
 		if (dirblocksize < blocksize ||
 					dirblocksize > XFS_MAX_BLOCKSIZE) {

@@ -2413,6 +2435,30 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 	mp->m_blkbb_log = sbp->sb_blocklog - BBSHIFT;
 	mp->m_sectbb_log = sbp->sb_sectlog - BBSHIFT;
 
+	/*
+	 * sb_versionnum and finobt flags must be set before we use
+	 * XFS_PREALLOC_BLOCKS().
+	 */
+	sbp->sb_features2 = XFS_SB_VERSION2_MKFS(crcs_enabled, lazy_sb_counters,
+					attrversion == 2, !projid16bit, 0,
+					(!crcs_enabled && dirftype));
+	sbp->sb_versionnum = XFS_SB_VERSION_MKFS(crcs_enabled, iaflag,
+					dsunit != 0,
+					logversion == 2, attrversion == 1,
+					(sectorsize != BBSIZE ||
+							lsectorsize != BBSIZE),
+					nci, sbp->sb_features2 != 0);
+	/*
+	 * Due to a structure alignment issue, sb_features2 ended up in one
+	 * of two locations, the second "incorrect" location represented by
+	 * the sb_bad_features2 field. To avoid older kernels mounting
+	 * filesystems they shouldn't, set both field to the same value.
+	 */
+	sbp->sb_bad_features2 = sbp->sb_features2;
+
+	if (finobt)
+		sbp->sb_features_ro_compat = XFS_SB_FEAT_RO_COMPAT_FINOBT;
+
 	if (loginternal) {
 		/*
 		 * Readjust the log size to fit within an AG if it was sized

@@ -2475,7 +2521,7 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 		printf(_(
 		   "meta-data=%-22s isize=%-6d agcount=%lld, agsize=%lld blks\n"
 		   "         =%-22s sectsz=%-5u attr=%u, projid32bit=%u\n"
-		   "         =%-22s crc=%u\n"
+		   "         =%-22s crc=%-8u finobt=%u\n"
 		   "data     =%-22s bsize=%-6u blocks=%llu, imaxpct=%u\n"
 		   "         =%-22s sunit=%-6u swidth=%u blks\n"
 		   "naming   =version %-14u bsize=%-6u ascii-ci=%d ftype=%d\n"

@@ -2484,7 +2530,7 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 		   "realtime =%-22s extsz=%-6d blocks=%lld, rtextents=%lld\n"),
 			dfile, isize, (long long)agcount, (long long)agsize,
 			"", sectorsize, attrversion, !projid16bit,
-			"", crcs_enabled,
+			"", crcs_enabled, finobt,
 			"", blocksize, (long long)dblocks, imaxpct,
 			"", dsunit, dswidth,
 			dirversion, dirblocksize, nci, dirftype,

@@ -2553,23 +2599,6 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 		sbp->sb_logsectsize = 0;
 	}
 
-	sbp->sb_features2 = XFS_SB_VERSION2_MKFS(crcs_enabled, lazy_sb_counters,
-				   attrversion == 2, !projid16bit, 0,
-				   (!crcs_enabled && dirftype));
-	sbp->sb_versionnum = XFS_SB_VERSION_MKFS(crcs_enabled, iaflag,
-					dsunit != 0,
-					logversion == 2, attrversion == 1,
-					(sectorsize != BBSIZE ||
-							lsectorsize != BBSIZE),
-					nci, sbp->sb_features2 != 0);
-	/*
-	 * Due to a structure alignment issue, sb_features2 ended up in one
-	 * of two locations, the second "incorrect" location represented by
-	 * the sb_bad_features2 field. To avoid older kernels mounting
-	 * filesystems they shouldn't, set both field to the same value.
-	 */
-	sbp->sb_bad_features2 = sbp->sb_features2;
-
 	if (force_overwrite)
 		zero_old_xfs_structures(&xi, sbp);
 

@@ -2726,6 +2755,10 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 		agi->agi_count = 0;
 		agi->agi_root = cpu_to_be32(XFS_IBT_BLOCK(mp));
 		agi->agi_level = cpu_to_be32(1);
+		if (finobt) {
+			agi->agi_free_root = cpu_to_be32(XFS_FIBT_BLOCK(mp));
+			agi->agi_free_level = cpu_to_be32(1);
+		}
 		agi->agi_freecount = 0;
 		agi->agi_newino = cpu_to_be32(NULLAGINO);
 		agi->agi_dirino = cpu_to_be32(NULLAGINO);

@@ -2851,6 +2884,26 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
 			xfs_btree_init_block(mp, buf, XFS_IBT_MAGIC, 0, 0,
 						agno, 0);
 		libxfs_writebuf(buf, LIBXFS_EXIT_ON_FAILURE);
+
+		/*
+		 * Free INO btree root block
+		 */
+		if (!finobt)
+			continue;
+
+		buf = libxfs_getbuf(mp->m_ddev_targp,
+				XFS_AGB_TO_DADDR(mp, agno, XFS_FIBT_BLOCK(mp)),
+				bsize);
+		buf->b_ops = &xfs_inobt_buf_ops;
+		block = XFS_BUF_TO_BLOCK(buf);
+		memset(block, 0, blocksize);
+		if (xfs_sb_version_hascrc(&mp->m_sb))
+			xfs_btree_init_block(mp, buf, XFS_FIBT_CRC_MAGIC, 0, 0,
+						agno, XFS_BTREE_CRC_BLOCKS);
+		else
+			xfs_btree_init_block(mp, buf, XFS_FIBT_MAGIC, 0, 0,
+						agno, 0);
+		libxfs_writebuf(buf, LIBXFS_EXIT_ON_FAILURE);
 	}
 
 	/*

@@ -3087,7 +3140,7 @@ usage( void )
 {
 	fprintf(stderr, _("Usage: %s\n\
 /* blocksize */		[-b log=n|size=num]\n\
-/* metadata */		[-m crc=[0|1]\n\
+/* metadata */		[-m crc=0|1,finobt=0|1]\n\
 /* data subvol */	[-d agcount=n,agsize=n,file,name=xxx,size=num,\n\
 			    (sunit=value,swidth=value|su=num,sw=num|noalign),\n\
 			    sectlog=n|sectsize=num\n\

index 398bdbb..6f167ac 100644
@@ -57,6 +57,8 @@ const field_t	agi_flds[] = {
 	{ "uuid", FLDT_UUID, OI(OFF(uuid)), C1, 0, TYP_NONE },
 	{ "lsn", FLDT_UINT64X, OI(OFF(lsn)), C1, 0, TYP_NONE },
 	{ "crc", FLDT_CRC, OI(OFF(crc)), C1, 0, TYP_NONE },
+	{ "free_root", FLDT_AGBLOCK, OI(OFF(free_root)), C1, 0, TYP_INOBT },
+	{ "free_level", FLDT_UINT32D, OI(OFF(free_level)), C1, 0, TYP_NONE },
 	{ NULL }
 };
 

index 1ea0cff..cdb8b1d 100644
@@ -60,6 +60,12 @@ struct xfs_db_btree {
 		sizeof(xfs_inobt_rec_t),
 		sizeof(__be32),
 	},
+	{	XFS_FIBT_MAGIC,
+		XFS_BTREE_SBLOCK_LEN,
+		sizeof(xfs_inobt_key_t),
+		sizeof(xfs_inobt_rec_t),
+		sizeof(__be32),
+	},
 	{	XFS_BMAP_CRC_MAGIC,
 		XFS_BTREE_LBLOCK_CRC_LEN,
 		sizeof(xfs_bmbt_key_t),

@@ -84,6 +90,12 @@ struct xfs_db_btree {
 		sizeof(xfs_inobt_rec_t),
 		sizeof(__be32),
 	},
+	{	XFS_FIBT_CRC_MAGIC,
+		XFS_BTREE_SBLOCK_CRC_LEN,
+		sizeof(xfs_inobt_key_t),
+		sizeof(xfs_inobt_rec_t),
+		sizeof(__be32),
+	},
 	{	0,
 	},
 };

index 08b25f0..9eb2fa4 100644
@@ -399,14 +399,18 @@ calc_mkfs(xfs_mount_t *mp)
 	do_inoalign = mp->m_sinoalign;
 
 	/*
-	 * pre-calculate geometry of ag 0.  We know what it looks
-	 * like because we know what mkfs does -- 3 btree roots,
-	 * and some number of blocks to prefill the agfl.
+	 * Pre-calculate the geometry of ag 0. We know what it looks like
+	 * because we know what mkfs does: 2 allocation btree roots (by block
+	 * and by size), the inode allocation btree root, the free inode
+	 * allocation btree root (if enabled) and some number of blocks to
+	 * prefill the agfl.
 	 */
 	bnobt_root = howmany(4 * mp->m_sb.sb_sectsize, mp->m_sb.sb_blocksize);
 	bcntbt_root = bnobt_root + 1;
 	inobt_root = bnobt_root + 2;
 	fino_bno = inobt_root + XFS_MIN_FREELIST_RAW(1, 1, mp) + 1;
+	if (xfs_sb_version_hasfinobt(&mp->m_sb))
+		fino_bno++;
 
 	/*
 	 * If the log is allocated in the first allocation group we need to

index 4b0ea04..1b64d8b 100644
@@ -46,6 +46,7 @@ struct aghdr_cnts {
 	__uint64_t	fdblocks;
 	__uint64_t	icount;
 	__uint64_t	ifreecount;
+	__uint32_t	fibtfreecount;
 };
 
 void

@@ -897,6 +898,208 @@ _("inode rec for ino %" PRIu64 " (%d/%d) overlaps existing rec (start %d/%d)\n")
 	return suspect;
 }
 
+static int
+scan_single_finobt_chunk(
+	xfs_agnumber_t		agno,
+	xfs_inobt_rec_t		*rp,
+	int			suspect)
+{
+	xfs_ino_t		lino;
+	xfs_agino_t		ino;
+	xfs_agblock_t		agbno;
+	int			j;
+	int			nfree;
+	int			off;
+	int			state;
+	ino_tree_node_t		*first_rec, *last_rec, *ino_rec;
+
+	ino = be32_to_cpu(rp->ir_startino);
+	off = XFS_AGINO_TO_OFFSET(mp, ino);
+	agbno = XFS_AGINO_TO_AGBNO(mp, ino);
+	lino = XFS_AGINO_TO_INO(mp, agno, ino);
+
+	/*
+	 * on multi-block block chunks, all chunks start at the beginning of the
+	 * block. with multi-chunk blocks, all chunks must start on 64-inode
+	 * boundaries since each block can hold N complete chunks. if fs has
+	 * aligned inodes, all chunks must start at a fs_ino_alignment*N'th
+	 * agbno. skip recs with badly aligned starting inodes.
+	 */
+	if (ino == 0 ||
+	    (inodes_per_block <= XFS_INODES_PER_CHUNK && off !=  0) ||
+	    (inodes_per_block > XFS_INODES_PER_CHUNK &&
+	     off % XFS_INODES_PER_CHUNK != 0) ||
+	    (fs_aligned_inodes && agbno % fs_ino_alignment != 0)) {
+		do_warn(
+	_("badly aligned finobt inode rec (starting inode = %" PRIu64 ")\n"),
+			lino);
+		suspect++;
+	}
+
+	/*
+	 * verify numeric validity of inode chunk first before inserting into a
+	 * tree. don't have to worry about the overflow case because the
+	 * starting ino number of a chunk can only get within 255 inodes of max
+	 * (NULLAGINO). if it gets closer, the agino number will be illegal as
+	 * the agbno will be too large.
+	 */
+	if (verify_aginum(mp, agno, ino)) {
+		do_warn(
+_("bad starting inode # (%" PRIu64 " (0x%x 0x%x)) in finobt rec, skipping rec\n"),
+			lino, agno, ino);
+		return ++suspect;
+	}
+
+	if (verify_aginum(mp, agno,
+			ino + XFS_INODES_PER_CHUNK - 1)) {
+		do_warn(
+_("bad ending inode # (%" PRIu64 " (0x%x 0x%zx)) in finobt rec, skipping rec\n"),
+			lino + XFS_INODES_PER_CHUNK - 1,
+			agno,
+			ino + XFS_INODES_PER_CHUNK - 1);
+		return ++suspect;
+	}
+
+	/*
+	 * cross check state of each block containing inodes referenced by the
+	 * finobt against what we have already scanned from the alloc inobt.
+	 */
+	if (off == 0 && !suspect) {
+		for (j = 0;
+		     j < XFS_INODES_PER_CHUNK;
+		     j += mp->m_sb.sb_inopblock) {
+			agbno = XFS_AGINO_TO_AGBNO(mp, ino + j);
+
+			state = get_bmap(agno, agbno);
+			if (state == XR_E_INO) {
+				continue;
+			} else if ((state == XR_E_UNKNOWN) ||
+				   (state == XR_E_INUSE_FS && agno == 0 &&
+				    ino + j >= first_prealloc_ino &&
+				    ino + j < last_prealloc_ino)) {
+				do_warn(
+_("inode chunk claims untracked block, finobt block - agno %d, bno %d, inopb %d\n"),
+					agno, agbno, mp->m_sb.sb_inopblock);
+
+				set_bmap(agno, agbno, XR_E_INO);
+				suspect++;
+			} else {
+				do_warn(
+_("inode chunk claims used block, finobt block - agno %d, bno %d, inopb %d\n"),
+					agno, agbno, mp->m_sb.sb_inopblock);
+				return ++suspect;
+			}
+		}
+	}
+
+	/*
+	 * ensure we have an incore entry for each chunk
+	 */
+	find_inode_rec_range(mp, agno, ino, ino + XFS_INODES_PER_CHUNK,
+			     &first_rec, &last_rec);
+
+	if (first_rec) {
+		if (suspect)
+			return suspect;
+
+		/*
+		 * verify consistency between finobt record and incore state
+		 */
+		if (first_rec->ino_startnum != ino) {
+			do_warn(
+_("finobt rec for ino %" PRIu64 " (%d/%u) does not match existing rec (%d/%d)\n"),
+				lino, agno, ino, agno, first_rec->ino_startnum);
+			return ++suspect;
+		}
+
+		nfree = 0;
+		for (j = 0; j < XFS_INODES_PER_CHUNK; j++) {
+			int isfree = XFS_INOBT_IS_FREE_DISK(rp, j);
+
+			if (isfree)
+				nfree++;
+
+			/*
+			 * inode allocation state should be consistent between
+			 * the inobt and finobt
+			 */
+			if (!suspect &&
+			    isfree != is_inode_free(first_rec, j))
+				suspect++;
+		}
+
+		goto check_freecount;
+	}
+
+	/*
+	 * the finobt contains a record that the previous alloc inobt scan never
+	 * found. insert the inodes into the appropriate tree.
+	 */
+	do_warn(_("undiscovered finobt record, ino %" PRIu64 " (%d/%u)\n"),
+		lino, agno, ino);
+
+	if (!suspect) {
+		/*
+		 * inodes previously inserted into the uncertain tree should be
+		 * superceded by these when the uncertain tree is processed
+		 */
+		nfree = 0;
+		if (XFS_INOBT_IS_FREE_DISK(rp, 0)) {
+			nfree++;
+			ino_rec = set_inode_free_alloc(mp, agno, ino);
+		} else  {
+			ino_rec = set_inode_used_alloc(mp, agno, ino);
+		}
+		for (j = 1; j < XFS_INODES_PER_CHUNK; j++) {
+			if (XFS_INOBT_IS_FREE_DISK(rp, j)) {
+				nfree++;
+				set_inode_free(ino_rec, j);
+			} else  {
+				set_inode_used(ino_rec, j);
+			}
+		}
+	} else {
+		/*
+		 * this should handle the case where the inobt scan may have
+		 * already added uncertain inodes
+		 */
+		nfree = 0;
+		for (j = 0; j < XFS_INODES_PER_CHUNK; j++) {
+			if (XFS_INOBT_IS_FREE_DISK(rp, j)) {
+				add_aginode_uncertain(mp, agno, ino + j, 1);
+				nfree++;
+			} else {
+				add_aginode_uncertain(mp, agno, ino + j, 0);
+			}
+		}
+	}
+
+check_freecount:
+
+	/*
+	 * Verify that the record freecount matches the actual number of free
+	 * inodes counted in the record. Don't increment 'suspect' here, since
+	 * we have already verified the allocation state of the individual
+	 * inodes against the in-core state. This will have already incremented
+	 * 'suspect' if something is wrong. If suspect hasn't been set at this
+	 * point, these warnings mean that we have a simple freecount
+	 * inconsistency or a stray finobt record (as opposed to a broader tree
+	 * corruption). Issue a warning and continue the scan. The final btree
+	 * reconstruction will correct this naturally.
+	 */
+	if (nfree != be32_to_cpu(rp->ir_freecount)) {
+		do_warn(
+_("finobt ir_freecount/free mismatch, inode chunk %d/%u, freecount %d nfree %d\n"),
+			agno, ino, be32_to_cpu(rp->ir_freecount), nfree);
+	}
+
+	if (!nfree) {
+		do_warn(
+_("finobt record with no free inodes, inode chunk %d/%u\n"), agno, ino);
+	}
+
+	return suspect;
+}
 
 /*
  * this one walks the inode btrees sucking the info there into

@@ -1005,12 +1208,29 @@ _("inode btree block claimed (state %d), agno %d, bno %d, suspect %d\n"),
 		 * the block.  skip processing of bogus records.
 		 */
 		for (i = 0; i < numrecs; i++) {
-			agcnts->agicount += XFS_INODES_PER_CHUNK;
-			agcnts->icount += XFS_INODES_PER_CHUNK;
-			agcnts->agifreecount += be32_to_cpu(rp[i].ir_freecount);
-			agcnts->ifreecount += be32_to_cpu(rp[i].ir_freecount);
+			if (magic == XFS_IBT_MAGIC ||
+			    magic == XFS_IBT_CRC_MAGIC) {
+				agcnts->agicount += XFS_INODES_PER_CHUNK;
+				agcnts->icount += XFS_INODES_PER_CHUNK;
+				agcnts->agifreecount +=
+					be32_to_cpu(rp[i].ir_freecount);
+				agcnts->ifreecount +=
+					be32_to_cpu(rp[i].ir_freecount);
+
+				suspect = scan_single_ino_chunk(agno, &rp[i],
+						suspect);
+			} else {
+				/*
+				 * the finobt tracks records with free inodes,
+				 * so only the free inode count is expected to be
+				 * consistent with the agi
+				 */
+				agcnts->fibtfreecount +=
+					be32_to_cpu(rp[i].ir_freecount);
 
-			suspect = scan_single_ino_chunk(agno, &rp[i], suspect);
+				suspect = scan_single_finobt_chunk(agno, &rp[i],
+						suspect);
+			}
 		}
 
 		if (suspect)

@@ -1198,6 +1418,20 @@ validate_agi(
 			be32_to_cpu(agi->agi_root), agno);
 	}
 
+	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
+		bno = be32_to_cpu(agi->agi_free_root);
+		if (bno != 0 && verify_agbno(mp, agno, bno)) {
+			magic = xfs_sb_version_hascrc(&mp->m_sb) ?
+					XFS_FIBT_CRC_MAGIC : XFS_FIBT_MAGIC;
+			scan_sbtree(bno, be32_to_cpu(agi->agi_free_level),
+				    agno, 0, scan_inobt, 1, magic, agcnts,
+				    &xfs_inobt_buf_ops);
+		} else {
+			do_warn(_("bad agbno %u for finobt root, agno %d\n"),
+				be32_to_cpu(agi->agi_free_root), agno);
+		}
+	}
+
 	if (be32_to_cpu(agi->agi_count) != agcnts->agicount) {
 		do_warn(_("agi_count %u, counted %u in ag %u\n"),
 			 be32_to_cpu(agi->agi_count), agcnts->agicount, agno);

@@ -1208,6 +1442,13 @@ validate_agi(
 			be32_to_cpu(agi->agi_freecount), agcnts->agifreecount, agno);
 	}
 
+	if (xfs_sb_version_hasfinobt(&mp->m_sb) &&
+	    be32_to_cpu(agi->agi_freecount) != agcnts->fibtfreecount) {
+		do_warn(_("agi_freecount %u, counted %u in ag %u finobt\n"),
+			be32_to_cpu(agi->agi_freecount), agcnts->fibtfreecount,
+			agno);
+	}
+
 	for (i = 0; i < XFS_AGI_UNLINKED_BUCKETS; i++) {
 		xfs_agino_t	agino = be32_to_cpu(agi->agi_unlinked[i]);
 

index b173597..2c02e40 100644
@@ -1094,7 +1094,7 @@ build_agi(xfs_mount_t *mp, xfs_agnumber_t agno,
  */
 static void
 build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
-		bt_status_t *btree_curs)
+		bt_status_t *btree_curs, __uint32_t magic)
 {
 	xfs_agnumber_t		i;
 	xfs_agblock_t		j;

@@ -1132,11 +1132,11 @@ build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
 		bt_hdr = XFS_BUF_TO_BLOCK(lptr->buf_p);
 		memset(bt_hdr, 0, mp->m_sb.sb_blocksize);
 		if (xfs_sb_version_hascrc(&mp->m_sb))
-			xfs_btree_init_block(mp, lptr->buf_p, XFS_IBT_CRC_MAGIC,
+			xfs_btree_init_block(mp, lptr->buf_p, magic,
 						i, 0, agno,
 						XFS_BTREE_CRC_BLOCKS);
 		else
-			xfs_btree_init_block(mp, lptr->buf_p, XFS_IBT_MAGIC,
+			xfs_btree_init_block(mp, lptr->buf_p, magic,
 						i, 0, agno, 0);
 	}
 

@@ -1163,11 +1163,11 @@ build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
 		bt_hdr = XFS_BUF_TO_BLOCK(lptr->buf_p);
 		memset(bt_hdr, 0, mp->m_sb.sb_blocksize);
 		if (xfs_sb_version_hascrc(&mp->m_sb))
-			xfs_btree_init_block(mp, lptr->buf_p, XFS_IBT_CRC_MAGIC,
+			xfs_btree_init_block(mp, lptr->buf_p, magic,
 						0, 0, agno,
 						XFS_BTREE_CRC_BLOCKS);
 		else
-			xfs_btree_init_block(mp, lptr->buf_p, XFS_IBT_MAGIC,
+			xfs_btree_init_block(mp, lptr->buf_p, magic,
 						0, 0, agno, 0);
 
 		bt_hdr->bb_u.s.bb_leftsib = cpu_to_be32(lptr->prev_agbno);

@@ -1480,6 +1480,7 @@ phase5_func(
 	xfs_extlen_t	freeblks2;
 #endif
 	xfs_agblock_t	num_extents;
+	__uint32_t	magic;
 
 	if (verbose)
 		do_log(_("        - agno = %d\n"), agno);

@@ -1613,7 +1614,9 @@ phase5_func(
 		/*
 		 * build inode allocation tree.  this also build the agi
 		 */
-		build_ino_tree(mp, agno, &ino_btree_curs);
+		magic = xfs_sb_version_hascrc(&mp->m_sb) ?
+				XFS_IBT_CRC_MAGIC : XFS_IBT_MAGIC;
+		build_ino_tree(mp, agno, &ino_btree_curs, magic);
 		write_cursor(&ino_btree_curs);
 		/*
 		 * tear down cursors

index 2c02e40..4778e08 100644
@@ -74,6 +74,15 @@ typedef struct bt_status  {
 	bt_stat_level_t		level[XFS_BTREE_MAXLEVELS];
 } bt_status_t;
 
+/*
+ * extra metadata for the agi
+ */
+struct agi_stat {
+	xfs_agino_t		first_agino;
+	xfs_agino_t		count;
+	xfs_agino_t		freecount;
+};
+
 static __uint64_t	*sb_icount_ag;		/* allocated inodes per ag */
 static __uint64_t	*sb_ifree_ag;		/* free inodes per ag */
 static __uint64_t	*sb_fdblocks_ag;	/* free data blocks per ag */

@@ -1050,8 +1059,7 @@ prop_ino_cursor(xfs_mount_t *mp, xfs_agnumber_t agno, bt_status_t *btree_curs,
  */
 static void
 build_agi(xfs_mount_t *mp, xfs_agnumber_t agno,
-		bt_status_t *btree_curs, xfs_agino_t first_agino,
-		xfs_agino_t count, xfs_agino_t freecount)
+		bt_status_t *btree_curs, struct agi_stat *agi_stat)
 {
 	xfs_buf_t	*agi_buf;
 	xfs_agi_t	*agi;

@@ -1072,11 +1080,11 @@ build_agi(xfs_mount_t *mp, xfs_agnumber_t agno,
 	else
 		agi->agi_length = cpu_to_be32(mp->m_sb.sb_dblocks -
 			(xfs_drfsbno_t) mp->m_sb.sb_agblocks * agno);
-	agi->agi_count = cpu_to_be32(count);
+	agi->agi_count = cpu_to_be32(agi_stat->count);
 	agi->agi_root = cpu_to_be32(btree_curs->root);
 	agi->agi_level = cpu_to_be32(btree_curs->num_levels);
-	agi->agi_freecount = cpu_to_be32(freecount);
-	agi->agi_newino = cpu_to_be32(first_agino);
+	agi->agi_freecount = cpu_to_be32(agi_stat->freecount);
+	agi->agi_newino = cpu_to_be32(agi_stat->first_agino);
 	agi->agi_dirino = cpu_to_be32(NULLAGINO);
 
 	for (i = 0; i < XFS_AGI_UNLINKED_BUCKETS; i++)  

@@ -1094,7 +1102,8 @@ build_agi(xfs_mount_t *mp, xfs_agnumber_t agno,
  */
 static void
 build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
-		bt_status_t *btree_curs, __uint32_t magic)
+		bt_status_t *btree_curs, __uint32_t magic,
+		struct agi_stat *agi_stat)
 {
 	xfs_agnumber_t		i;
 	xfs_agblock_t		j;

@@ -1224,7 +1233,11 @@ build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
 		}
 	}
 
-	build_agi(mp, agno, btree_curs, first_agino, count, freecount);
+	if (agi_stat) {
+		agi_stat->first_agino = first_agino;
+		agi_stat->count = count;
+		agi_stat->freecount = freecount;
+	}
 }
 
 /*

@@ -1481,6 +1494,7 @@ phase5_func(
 #endif
 	xfs_agblock_t	num_extents;
 	__uint32_t	magic;
+	struct agi_stat	agi_stat = {0,};
 
 	if (verbose)
 		do_log(_("        - agno = %d\n"), agno);

@@ -1612,12 +1626,16 @@ phase5_func(
 		build_agf_agfl(mp, agno, &bno_btree_curs,
 				&bcnt_btree_curs, freeblks1, extra_blocks);
 		/*
-		 * build inode allocation tree.  this also build the agi
+		 * build inode allocation tree.
 		 */
 		magic = xfs_sb_version_hascrc(&mp->m_sb) ?
 				XFS_IBT_CRC_MAGIC : XFS_IBT_MAGIC;
-		build_ino_tree(mp, agno, &ino_btree_curs, magic);
+		build_ino_tree(mp, agno, &ino_btree_curs, magic, &agi_stat);
 		write_cursor(&ino_btree_curs);
+
+		/* build the agi */
+		build_agi(mp, agno, &ino_btree_curs, &agi_stat);
+
 		/*
 		 * tear down cursors
 		 */

index 5419884..5f8c188 100644
@@ -381,6 +381,33 @@ void			clear_uncertain_ino_cache(xfs_agnumber_t agno);
 		((ino_tree_node_t *) ((ino_node_ptr)->avl_node.avl_forw))
 
 /*
+ * finobt helpers
+ */
+static inline ino_tree_node_t *
+findfirst_free_inode_rec(xfs_agnumber_t agno)
+{
+	ino_tree_node_t *ino_rec;
+
+	ino_rec = findfirst_inode_rec(agno);
+
+	while (ino_rec && !ino_rec->ir_free)
+		ino_rec = next_ino_rec(ino_rec);
+
+	return ino_rec;
+}
+
+static inline ino_tree_node_t *
+next_free_ino_rec(ino_tree_node_t *ino_rec)
+{
+	ino_rec = next_ino_rec(ino_rec);
+
+	while (ino_rec && !ino_rec->ir_free)
+		ino_rec = next_ino_rec(ino_rec);
+
+	return ino_rec;
+}
+
+/*
  * Has an inode been processed for phase 6 (reference count checking)?
  *
  * add_inode_refchecked() is set on an inode when it gets traversed

index 4778e08..e82eeb7 100644
@@ -878,10 +878,11 @@ build_freespace_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
  */
 static void
 init_ino_cursor(xfs_mount_t *mp, xfs_agnumber_t agno, bt_status_t *btree_curs,
-		__uint64_t *num_inos, __uint64_t *num_free_inos)
+		__uint64_t *num_inos, __uint64_t *num_free_inos, int finobt)
 {
 	__uint64_t		ninos;
 	__uint64_t		nfinos;
+	__uint64_t		rec_nfinos;
 	ino_tree_node_t		*ino_rec;
 	int			num_recs;
 	int			level;

@@ -917,13 +918,22 @@ init_ino_cursor(xfs_mount_t *mp, xfs_agnumber_t agno, bt_status_t *btree_curs,
 	 * build up statistics
 	 */
 	for (num_recs = 0; ino_rec != NULL; ino_rec = next_ino_rec(ino_rec))  {
-		ninos += XFS_INODES_PER_CHUNK;
-		num_recs++;
+		rec_nfinos = 0;
 		for (i = 0; i < XFS_INODES_PER_CHUNK; i++)  {
 			ASSERT(is_inode_confirmed(ino_rec, i));
 			if (is_inode_free(ino_rec, i))
-				nfinos++;
+				rec_nfinos++;
 		}
+
+		/*
+		 * finobt only considers records with free inodes
+		 */
+		if (finobt && !rec_nfinos)
+			continue;
+
+		nfinos += rec_nfinos;
+		ninos += XFS_INODES_PER_CHUNK;
+		num_recs++;
 	}
 
 	blocks_allocated = lptr->num_blocks = howmany(num_recs,

@@ -1058,8 +1068,8 @@ prop_ino_cursor(xfs_mount_t *mp, xfs_agnumber_t agno, bt_status_t *btree_curs,
  * XXX: yet more code that can be shared with mkfs, growfs.
  */
 static void
-build_agi(xfs_mount_t *mp, xfs_agnumber_t agno,
-		bt_status_t *btree_curs, struct agi_stat *agi_stat)
+build_agi(xfs_mount_t *mp, xfs_agnumber_t agno, bt_status_t *btree_curs,
+		bt_status_t *finobt_curs, struct agi_stat *agi_stat)
 {
 	xfs_buf_t	*agi_buf;
 	xfs_agi_t	*agi;

@@ -1093,6 +1103,11 @@ build_agi(xfs_mount_t *mp, xfs_agnumber_t agno,
 	if (xfs_sb_version_hascrc(&mp->m_sb))
 		platform_uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_uuid);
 
+	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
+		agi->agi_free_root = cpu_to_be32(finobt_curs->root);
+		agi->agi_free_level = cpu_to_be32(finobt_curs->num_levels);
+	}
+
 	libxfs_writebuf(agi_buf, 0);
 }
 

@@ -1103,7 +1118,7 @@ build_agi(xfs_mount_t *mp, xfs_agnumber_t agno,
 static void
 build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
 		bt_status_t *btree_curs, __uint32_t magic,
-		struct agi_stat *agi_stat)
+		struct agi_stat *agi_stat, int finobt)
 {
 	xfs_agnumber_t		i;
 	xfs_agblock_t		j;

@@ -1155,7 +1170,10 @@ build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
 	 * pointers for the parent.  that can recurse up to the root
 	 * if required.  set the sibling pointers for leaf level here.
 	 */
-	ino_rec = findfirst_inode_rec(agno);
+	if (finobt)
+		ino_rec = findfirst_free_inode_rec(agno);
+	else
+		ino_rec = findfirst_inode_rec(agno);
 
 	if (ino_rec != NULL)
 		first_agino = ino_rec->ino_startnum;

@@ -1207,7 +1225,11 @@ build_ino_tree(xfs_mount_t *mp, xfs_agnumber_t agno,
 			bt_rec[j].ir_freecount = cpu_to_be32(inocnt);
 			freecount += inocnt;
 			count += XFS_INODES_PER_CHUNK;
-			ino_rec = next_ino_rec(ino_rec);
+
+			if (finobt)
+				ino_rec = next_free_ino_rec(ino_rec);
+			else
+				ino_rec = next_ino_rec(ino_rec);
 		}
 
 		if (ino_rec != NULL)  {

@@ -1483,9 +1505,12 @@ phase5_func(
 {
 	__uint64_t	num_inos;
 	__uint64_t	num_free_inos;
+	__uint64_t	finobt_num_inos;
+	__uint64_t	finobt_num_free_inos;
 	bt_status_t	bno_btree_curs;
 	bt_status_t	bcnt_btree_curs;
 	bt_status_t	ino_btree_curs;
+	bt_status_t	fino_btree_curs;
 	int		extra_blocks = 0;
 	uint		num_freeblocks;
 	xfs_extlen_t	freeblks1;

@@ -1530,8 +1555,13 @@ phase5_func(
 		 * on-disk btrees (includs pre-allocating all
 		 * required blocks for the trees themselves)
 		 */
-		init_ino_cursor(mp, agno, &ino_btree_curs,
-				&num_inos, &num_free_inos);
+		init_ino_cursor(mp, agno, &ino_btree_curs, &num_inos,
+				&num_free_inos, 0);
+
+		if (xfs_sb_version_hasfinobt(&mp->m_sb))
+			init_ino_cursor(mp, agno, &fino_btree_curs,
+					&finobt_num_inos, &finobt_num_free_inos,
+					1);
 
 		sb_icount_ag[agno] += num_inos;
 		sb_ifree_ag[agno] += num_free_inos;

@@ -1630,17 +1660,31 @@ phase5_func(
 		 */
 		magic = xfs_sb_version_hascrc(&mp->m_sb) ?
 				XFS_IBT_CRC_MAGIC : XFS_IBT_MAGIC;
-		build_ino_tree(mp, agno, &ino_btree_curs, magic, &agi_stat);
+		build_ino_tree(mp, agno, &ino_btree_curs, magic, &agi_stat, 0);
 		write_cursor(&ino_btree_curs);
 
+		/*
+		 * build free inode tree
+		 */
+		if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
+			magic = xfs_sb_version_hascrc(&mp->m_sb) ?
+					XFS_FIBT_CRC_MAGIC : XFS_FIBT_MAGIC;
+			build_ino_tree(mp, agno, &fino_btree_curs, magic,
+					NULL, 1);
+			write_cursor(&fino_btree_curs);
+		}
+
 		/* build the agi */
-		build_agi(mp, agno, &ino_btree_curs, &agi_stat);
+		build_agi(mp, agno, &ino_btree_curs, &fino_btree_curs,
+			  &agi_stat);
 
 		/*
 		 * tear down cursors
 		 */
 		finish_cursor(&bno_btree_curs);
 		finish_cursor(&ino_btree_curs);
+		if (xfs_sb_version_hasfinobt(&mp->m_sb))
+			finish_cursor(&fino_btree_curs);
 		finish_cursor(&bcnt_btree_curs);
 		/*
 		 * release the incore per-AG bno/bcnt trees so

index 77da707..8e611b6 100644
@@ -56,12 +56,13 @@ report_info(
 	int		projid32bit,
 	int		crcs_enabled,
 	int		cimode,
-	int		ftype_enabled)
+	int		ftype_enabled,
+	int		finobt_enabled)
 {
 	printf(_(
 	    "meta-data=%-22s isize=%-6u agcount=%u, agsize=%u blks\n"
 	    "         =%-22s sectsz=%-5u attr=%u, projid32bit=%u\n"
-	    "         =%-22s crc=%u\n"
+	    "         =%-22s crc=%-8u finobt=%u\n"
 	    "data     =%-22s bsize=%-6u blocks=%llu, imaxpct=%u\n"
 	    "         =%-22s sunit=%-6u swidth=%u blks\n"
 	    "naming   =version %-14u bsize=%-6u ascii-ci=%d ftype=%d\n"

@@ -71,7 +72,7 @@ report_info(
 
 		mntpoint, geo.inodesize, geo.agcount, geo.agblocks,
 		"", geo.sectsize, attrversion, projid32bit,
-		"", crcs_enabled,
+		"", crcs_enabled, finobt_enabled,
 		"", geo.blocksize, (unsigned long long)geo.datablocks,
 			geo.imaxpct,
 		"", geo.sunit, geo.swidth,

@@ -123,6 +124,7 @@ main(int argc, char **argv)
 	int			projid32bit;
 	int			crcs_enabled;
 	int			ftype_enabled = 0;
+	int			finobt_enabled;	/* free inode btree */
 
 	progname = basename(argv[0]);
 	setlocale(LC_ALL, "");

@@ -244,11 +246,12 @@ main(int argc, char **argv)
 	projid32bit = geo.flags & XFS_FSOP_GEOM_FLAGS_PROJID32 ? 1 : 0;
 	crcs_enabled = geo.flags & XFS_FSOP_GEOM_FLAGS_V5SB ? 1 : 0;
 	ftype_enabled = geo.flags & XFS_FSOP_GEOM_FLAGS_FTYPE ? 1 : 0;
+	finobt_enabled = geo.flags & XFS_FSOP_GEOM_FLAGS_FINOBT ? 1 : 0;
 	if (nflag) {
 		report_info(geo, datadev, isint, logdev, rtdev,
 				lazycount, dirversion, logversion,
 				attrversion, projid32bit, crcs_enabled, ci,
-				ftype_enabled);
+				ftype_enabled, finobt_enabled);
 		exit(0);
 	}
 

@@ -285,7 +288,8 @@ main(int argc, char **argv)
 
 	report_info(geo, datadev, isint, logdev, rtdev,
 			lazycount, dirversion, logversion,
-			attrversion, projid32bit, crcs_enabled, ci, ftype_enabled);
+			attrversion, projid32bit, crcs_enabled, ci, ftype_enabled,
+			finobt_enabled);
 
 	ddsize = xi.dsize;
 	dlsize = ( xi.logBBsize? xi.logBBsize :

index 09bb85a..38cd441 100644
@@ -1917,6 +1917,7 @@ scanfunc_ino(
 	xfs_inobt_ptr_t		*pp;
 	int			i;
 	int			numrecs;
+	int			finobt = *(int *) arg;
 
 	numrecs = be16_to_cpu(block->bb_numrecs);
 

@@ -1928,6 +1929,14 @@ scanfunc_ino(
 					typtab[btype].name, agno, agbno);
 			numrecs = mp->m_inobt_mxr[0];
 		}
+
+		/*
+		 * Only copy the btree blocks for the finobt. The inobt scan
+		 * copies the inode chunks.
+		 */
+		if (finobt)
+			return 1;
+
 		rp = XFS_INOBT_REC_ADDR(mp, block, 1);
 		for (i = 0; i < numrecs; i++, rp++) {
 			if (!copy_inode_chunk(agno, rp))

@@ -1967,6 +1976,7 @@ copy_inodes(
 {
 	xfs_agblock_t		root;
 	int			levels;
+	int			finobt = 0;
 
 	root = be32_to_cpu(agi->agi_root);
 	levels = be32_to_cpu(agi->agi_level);

@@ -1985,7 +1995,20 @@ copy_inodes(
 		return 1;
 	}
 
-	return scan_btree(agno, root, levels, TYP_INOBT, agi, scanfunc_ino);
+	if (!scan_btree(agno, root, levels, TYP_INOBT, &finobt, scanfunc_ino))
+		return 0;
+
+	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
+		root = be32_to_cpu(agi->agi_free_root);
+		levels = be32_to_cpu(agi->agi_free_level);
+
+		finobt = 1;
+		if (!scan_btree(agno, root, levels, TYP_INOBT, &finobt,
+				scanfunc_ino))
+			return 0;
+	}
+
+	return 1;
 }
 
 static int