diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 16b983b8977d..8788f47ba59e 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -52,9 +52,9 @@ xfs_bmap_compute_maxlevels(
 	xfs_mount_t	*mp,		/* file system mount structure */
 	int		whichfork)	/* data or attr fork */
 {
+	xfs_extnum_t	maxleafents;	/* max leaf entries possible */
 	int		level;		/* btree level */
 	uint		maxblocks;	/* max blocks at this level */
-	uint		maxleafents;	/* max leaf entries possible */
 	int		maxrootrecs;	/* max records in root block */
 	int		minleafrecs;	/* min records in leaf block */
 	int		minnoderecs;	/* min records in node block */
@@ -64,7 +64,9 @@ xfs_bmap_compute_maxlevels(
 	 * The maximum number of extents in a file, hence the maximum number of
 	 * leaf entries, is controlled by the size of the on-disk extent count,
 	 * either a signed 32-bit number for the data fork, or a signed 16-bit
-	 * number for the attr fork.
+	 * number for the attr fork. With mkfs.xfs' wide-extcount option
+	 * enabled, the data fork extent count is unsigned 47-bits wide, while
+	 * the corresponding attr fork extent count is unsigned 32-bits wide.
 	 *
 	 * Note that we can no longer assume that if we are in ATTR1 that
 	 * the fork offset of all the inodes will be
@@ -464,7 +466,7 @@ xfs_bmap_check_leaf_extents(
 	if (bp_release)
 		xfs_trans_brelse(NULL, bp);
 error_norelse:
-	xfs_warn(mp, "%s: BAD after btree leaves for %d extents",
+	xfs_warn(mp, "%s: BAD after btree leaves for %llu extents",
 		__func__, i);
 	xfs_err(mp, "%s: CORRUPTED BTREE OR SOMETHING", __func__);
 	xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 5f41e177dbda..2684cafd0356 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -465,10 +465,12 @@ xfs_sb_has_ro_compat_feature(
 #define XFS_SB_FEAT_INCOMPAT_FTYPE	(1 << 0)	/* filetype in dirent */
 #define XFS_SB_FEAT_INCOMPAT_SPINODES	(1 << 1)	/* sparse inode chunks */
 #define XFS_SB_FEAT_INCOMPAT_META_UUID	(1 << 2)	/* metadata UUID */
-#define XFS_SB_FEAT_INCOMPAT_ALL \
+#define XFS_SB_FEAT_INCOMPAT_WIDEEXTCNT	(1 << 3)	/* Wider data/attr fork extent counters */
+#define XFS_SB_FEAT_INCOMPAT_ALL		\
 		(XFS_SB_FEAT_INCOMPAT_FTYPE|	\
 		 XFS_SB_FEAT_INCOMPAT_SPINODES|	\
-		 XFS_SB_FEAT_INCOMPAT_META_UUID)
+		 XFS_SB_FEAT_INCOMPAT_META_UUID| \
+		 XFS_SB_FEAT_INCOMPAT_WIDEEXTCNT)
 
 #define XFS_SB_FEAT_INCOMPAT_UNKNOWN	~XFS_SB_FEAT_INCOMPAT_ALL
 static inline bool
@@ -551,6 +553,12 @@ static inline bool xfs_sb_version_hasmetauuid(struct xfs_sb *sbp)
 		(sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_META_UUID);
 }
 
+static inline bool xfs_sb_version_haswideextcnt(struct xfs_sb *sbp)
+{
+	return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) &&
+		(sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_WIDEEXTCNT);
+}
+
 static inline bool xfs_sb_version_hasrmapbt(struct xfs_sb *sbp)
 {
 	return (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5) &&
@@ -873,8 +881,8 @@ typedef struct xfs_dinode {
 	__be64		di_size;	/* number of bytes in file */
 	__be64		di_nblocks;	/* # of direct & btree blocks used */
 	__be32		di_extsize;	/* basic/minimum extent size for file */
-	__be32		di_nextents;	/* number of extents in data fork */
-	__be16		di_anextents;	/* number of extents in attribute fork*/
+	__be32		di_nextents_lo;	/* lower part of data fork extent count */
+	__be16		di_anextents_lo;/* lower part of attr fork extent count */
 	__u8		di_forkoff;	/* attr fork offs, <<3 for 64b align */
 	__s8		di_aformat;	/* format of attr fork's data */
 	__be32		di_dmevmask;	/* DMIG event mask */
@@ -891,7 +899,9 @@ typedef struct xfs_dinode {
 	__be64		di_lsn;		/* flush sequence */
 	__be64		di_flags2;	/* more random flags */
 	__be32		di_cowextsize;	/* basic cow extent size for file */
-	__u8		di_pad2[12];	/* more padding for future expansion */
+	__be32		di_nextents_hi; /* higher part of data fork extent count */
+	__be16		di_anextents_hi;/* higher part of attr fork extent count */
+	__u8		di_pad2[6];	/* more padding for future expansion */
 
 	/* fields only written to during inode creation */
 	xfs_timestamp_t	di_crtime;	/* time created */
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index cce2aa99aad8..8212bd4b12db 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -258,6 +258,7 @@ xfs_inode_to_disk(
 	struct xfs_dinode	*to,
 	xfs_lsn_t		lsn)
 {
+	struct xfs_sb		*sbp = &ip->i_mount->m_sb;
 	struct xfs_icdinode	*from = &ip->i_d;
 	struct inode		*inode = VFS_I(ip);
 
@@ -284,8 +285,8 @@ xfs_inode_to_disk(
 	to->di_size = cpu_to_be64(from->di_size);
 	to->di_nblocks = cpu_to_be64(from->di_nblocks);
 	to->di_extsize = cpu_to_be32(from->di_extsize);
-	to->di_nextents = cpu_to_be32(xfs_ifork_nextents(&ip->i_df));
-	to->di_anextents = cpu_to_be16(xfs_ifork_nextents(ip->i_afp));
+	to->di_nextents_lo = cpu_to_be32(xfs_ifork_nextents(&ip->i_df));
+	to->di_anextents_lo = cpu_to_be16(xfs_ifork_nextents(ip->i_afp));
 	to->di_forkoff = from->di_forkoff;
 	to->di_aformat = xfs_ifork_format(ip->i_afp);
 	to->di_dmevmask = cpu_to_be32(from->di_dmevmask);
@@ -299,6 +300,15 @@ xfs_inode_to_disk(
 		to->di_crtime.t_nsec = cpu_to_be32(from->di_crtime.tv_nsec);
 		to->di_flags2 = cpu_to_be64(from->di_flags2);
 		to->di_cowextsize = cpu_to_be32(from->di_cowextsize);
+		if (xfs_sb_version_haswideextcnt(sbp)) {
+			to->di_nextents_hi
+				= cpu_to_be32(xfs_ifork_nextents(&ip->i_df)
+					>> 32);
+			to->di_anextents_hi
+				= cpu_to_be16(xfs_ifork_nextents(ip->i_afp)
+					>> 16);
+		}
+
 		to->di_ino = cpu_to_be64(ip->i_ino);
 		to->di_lsn = cpu_to_be64(lsn);
 		memset(to->di_pad2, 0, sizeof(to->di_pad2));
@@ -312,9 +322,12 @@ xfs_inode_to_disk(
 
 void
 xfs_log_dinode_to_disk(
+	struct xfs_mount	*mp,
 	struct xfs_log_dinode	*from,
 	struct xfs_dinode	*to)
 {
+	struct xfs_sb		*sbp = &mp->m_sb;
+
 	to->di_magic = cpu_to_be16(from->di_magic);
 	to->di_mode = cpu_to_be16(from->di_mode);
 	to->di_version = from->di_version;
@@ -337,8 +350,8 @@ xfs_log_dinode_to_disk(
 	to->di_size = cpu_to_be64(from->di_size);
 	to->di_nblocks = cpu_to_be64(from->di_nblocks);
 	to->di_extsize = cpu_to_be32(from->di_extsize);
-	to->di_nextents = cpu_to_be32(from->di_nextents);
-	to->di_anextents = cpu_to_be16(from->di_anextents);
+	to->di_nextents_lo = cpu_to_be32(from->di_nextents_lo);
+	to->di_anextents_lo = cpu_to_be16(from->di_anextents_lo);
 	to->di_forkoff = from->di_forkoff;
 	to->di_aformat = from->di_aformat;
 	to->di_dmevmask = cpu_to_be32(from->di_dmevmask);
@@ -352,6 +365,10 @@ xfs_log_dinode_to_disk(
 		to->di_crtime.t_nsec = cpu_to_be32(from->di_crtime.t_nsec);
 		to->di_flags2 = cpu_to_be64(from->di_flags2);
 		to->di_cowextsize = cpu_to_be32(from->di_cowextsize);
+		if (xfs_sb_version_haswideextcnt(sbp)) {
+			to->di_nextents_hi = cpu_to_be32(from->di_nextents_hi);
+			to->di_anextents_hi = cpu_to_be16(from->di_anextents_hi);
+		}
 		to->di_ino = cpu_to_be64(from->di_ino);
 		to->di_lsn = cpu_to_be64(from->di_lsn);
 		memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
@@ -368,7 +385,7 @@ xfs_dinode_verify_fork(
 	struct xfs_mount	*mp,
 	int			whichfork)
 {
-	uint32_t		di_nextents;
+	xfs_extnum_t		di_nextents;
 	xfs_extnum_t		max_extents;
 
 	di_nextents = xfs_dfork_nextents(&mp->m_sb, dip, whichfork);
@@ -408,10 +425,17 @@ xfs_dfork_nextents(struct xfs_sb *sbp, struct xfs_dinode *dip, int whichfork)
 {
 	xfs_extnum_t nextents;
 
-	if (whichfork == XFS_DATA_FORK)
-		nextents = be32_to_cpu(dip->di_nextents);
-	else
-		nextents = be16_to_cpu(dip->di_anextents);
+	if (whichfork == XFS_DATA_FORK) {
+		nextents = be32_to_cpu(dip->di_nextents_lo);
+		if (xfs_sb_version_haswideextcnt(sbp))
+			nextents |=
+				((xfs_extnum_t)be32_to_cpu(dip->di_nextents_hi) << 32);
+	} else {
+		nextents = be16_to_cpu(dip->di_anextents_lo);
+		if (xfs_sb_version_haswideextcnt(sbp))
+			nextents |=
+				((xfs_aextnum_t)be16_to_cpu(dip->di_anextents_hi) << 16);
+	}
 
 	return nextents;
 }
diff --git a/fs/xfs/libxfs/xfs_inode_buf.h b/fs/xfs/libxfs/xfs_inode_buf.h
index a97caf675aaf..288ac17626fd 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.h
+++ b/fs/xfs/libxfs/xfs_inode_buf.h
@@ -49,8 +49,8 @@ void	xfs_dinode_calc_crc(struct xfs_mount *, struct xfs_dinode *);
 void	xfs_inode_to_disk(struct xfs_inode *ip, struct xfs_dinode *to,
 			  xfs_lsn_t lsn);
 int	xfs_inode_from_disk(struct xfs_inode *ip, struct xfs_dinode *from);
-void	xfs_log_dinode_to_disk(struct xfs_log_dinode *from,
-			       struct xfs_dinode *to);
+void	xfs_log_dinode_to_disk(struct xfs_mount *mp,
+		struct xfs_log_dinode *from, struct xfs_dinode *to);
 
 xfs_failaddr_t xfs_dinode_verify(struct xfs_mount *mp, xfs_ino_t ino,
 			   struct xfs_dinode *dip);
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 75e07078967e..bc9246d1fd78 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -21,10 +21,10 @@ struct xfs_ifork {
 		void		*if_root;	/* extent tree root */
 		char		*if_data;	/* inline file data */
 	} if_u1;
+	xfs_extnum_t		if_nextents;	/* # of extents in this fork */
 	short			if_broot_bytes;	/* bytes allocated for root */
 	unsigned char		if_flags;	/* per-fork flags */
 	int8_t			if_format;	/* format of this fork */
-	xfs_extnum_t		if_nextents;	/* # of extents in this fork */
 };
 
 /*
@@ -157,10 +157,17 @@ static inline xfs_extnum_t xfs_iext_max(struct xfs_sb *sbp, int whichfork)
 {
 	ASSERT(whichfork == XFS_DATA_FORK || whichfork == XFS_ATTR_FORK);
 
-	if (whichfork == XFS_DATA_FORK)
-		return MAXEXTNUM;
-	else
-		return MAXAEXTNUM;
+	if (whichfork == XFS_DATA_FORK) {
+		if (xfs_sb_version_haswideextcnt(sbp))
+			return MAXEXTNUM_HI;
+		else
+			return MAXEXTNUM;
+	} else {
+		if (xfs_sb_version_haswideextcnt(sbp))
+			return MAXAEXTNUM_HI;
+		else
+			return MAXAEXTNUM;
+	}
 }
 
 struct xfs_ifork *xfs_iext_state_to_fork(struct xfs_inode *ip, int state);
diff --git a/fs/xfs/libxfs/xfs_log_format.h b/fs/xfs/libxfs/xfs_log_format.h
index e3400c9c71cd..938883c0218d 100644
--- a/fs/xfs/libxfs/xfs_log_format.h
+++ b/fs/xfs/libxfs/xfs_log_format.h
@@ -396,8 +396,8 @@ struct xfs_log_dinode {
 	xfs_fsize_t	di_size;	/* number of bytes in file */
 	xfs_rfsblock_t	di_nblocks;	/* # of direct & btree blocks used */
 	xfs_extlen_t	di_extsize;	/* basic/minimum extent size for file */
-	xfs_extnum_t	di_nextents;	/* number of extents in data fork */
-	xfs_aextnum_t	di_anextents;	/* number of extents in attribute fork*/
+	uint32_t	di_nextents_lo;	/* lower part of data fork extent count */
+	uint16_t	di_anextents_lo;/* lower part of attr fork extent count */
 	uint8_t		di_forkoff;	/* attr fork offs, <<3 for 64b align */
 	int8_t		di_aformat;	/* format of attr fork's data */
 	uint32_t	di_dmevmask;	/* DMIG event mask */
@@ -414,7 +414,9 @@ struct xfs_log_dinode {
 	xfs_lsn_t	di_lsn;		/* flush sequence */
 	uint64_t	di_flags2;	/* more random flags */
 	uint32_t	di_cowextsize;	/* basic cow extent size for file */
-	uint8_t		di_pad2[12];	/* more padding for future expansion */
+	uint32_t	di_nextents_hi; /* higher part of data fork extent count */
+	uint16_t	di_anextents_hi;/* higher part of attr fork extent count */
+	uint8_t		di_pad2[6];	/* more padding for future expansion */
 
 	/* fields only written to during inode creation */
 	xfs_ictimestamp_t di_crtime;	/* time created */
diff --git a/fs/xfs/libxfs/xfs_types.h b/fs/xfs/libxfs/xfs_types.h
index 397d94775440..c302a89d5c63 100644
--- a/fs/xfs/libxfs/xfs_types.h
+++ b/fs/xfs/libxfs/xfs_types.h
@@ -12,8 +12,8 @@ typedef uint32_t	xfs_agblock_t;	/* blockno in alloc. group */
 typedef uint32_t	xfs_agino_t;	/* inode # within allocation grp */
 typedef uint32_t	xfs_extlen_t;	/* extent length in blocks */
 typedef uint32_t	xfs_agnumber_t;	/* allocation group number */
-typedef int32_t		xfs_extnum_t;	/* # of extents in a file */
-typedef int16_t		xfs_aextnum_t;	/* # extents in an attribute fork */
+typedef uint64_t	xfs_extnum_t;	/* # of extents in a file */
+typedef uint32_t	xfs_aextnum_t;	/* # extents in an attribute fork */
 typedef int64_t		xfs_fsize_t;	/* bytes in a file */
 typedef uint64_t	xfs_ufsize_t;	/* unsigned bytes in a file */
 
@@ -59,8 +59,10 @@ typedef void *		xfs_failaddr_t;
  * Max values for extlen, extnum, aextnum.
  */
 #define	MAXEXTLEN	((xfs_extlen_t)0x001fffff)	/* 21 bits */
-#define	MAXEXTNUM	((xfs_extnum_t)0x7fffffff)	/* signed int */
-#define	MAXAEXTNUM	((xfs_aextnum_t)0x7fff)		/* signed short */
+#define	MAXEXTNUM	((int32_t)0x7fffffff)		/* signed int */
+#define	MAXAEXTNUM	((int16_t)0x7fff)		/* signed short */
+#define MAXEXTNUM_HI	((xfs_extnum_t)0x7fffffffffff)	/* unsigned 47 bits */
+#define MAXAEXTNUM_HI	((xfs_aextnum_t)0xffffffff)	/* unsigned 32 bits */
 
 /*
  * Minimum and maximum blocksize and sectorsize.
diff --git a/fs/xfs/scrub/inode.c b/fs/xfs/scrub/inode.c
index e428ad0eef03..e6a58e59720e 100644
--- a/fs/xfs/scrub/inode.c
+++ b/fs/xfs/scrub/inode.c
@@ -206,7 +206,7 @@ xchk_dinode(
 	size_t			fork_recs;
 	unsigned long long	isize;
 	uint64_t		flags2;
-	uint32_t		nextents;
+	xfs_extnum_t		nextents;
 	uint16_t		flags;
 	uint16_t		mode;
 
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 8d195b6ef326..d11d22f7755b 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3517,7 +3517,7 @@ xfs_iflush(
 				ip->i_d.di_nblocks, mp, XFS_ERRTAG_IFLUSH_5)) {
 		xfs_alert_tag(mp, XFS_PTAG_IFLUSH,
 			"%s: detected corrupt incore inode %Lu, "
-			"total extents = %d, nblocks = %Ld, ptr "PTR_FMT,
+			"total extents = %llu, nblocks = %Ld, ptr "PTR_FMT,
 			__func__, ip->i_ino,
 			ip->i_df.if_nextents + xfs_ifork_nextents(ip->i_afp),
 			ip->i_d.di_nblocks, ip);
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 895f61b2b4f0..a65fd62237c6 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -301,6 +301,7 @@ xfs_inode_to_log_dinode(
 	struct xfs_log_dinode	*to,
 	xfs_lsn_t		lsn)
 {
+	struct xfs_sb		*sbp = &ip->i_mount->m_sb;
 	struct xfs_icdinode	*from = &ip->i_d;
 	struct inode		*inode = VFS_I(ip);
 
@@ -326,8 +327,8 @@ xfs_inode_to_log_dinode(
 	to->di_size = from->di_size;
 	to->di_nblocks = from->di_nblocks;
 	to->di_extsize = from->di_extsize;
-	to->di_nextents = xfs_ifork_nextents(&ip->i_df);
-	to->di_anextents = xfs_ifork_nextents(ip->i_afp);
+	to->di_nextents_lo = xfs_ifork_nextents(&ip->i_df);
+	to->di_anextents_lo = xfs_ifork_nextents(ip->i_afp);
 	to->di_forkoff = from->di_forkoff;
 	to->di_aformat = xfs_ifork_format(ip->i_afp);
 	to->di_dmevmask = from->di_dmevmask;
@@ -344,6 +345,13 @@ xfs_inode_to_log_dinode(
 		to->di_crtime.t_nsec = from->di_crtime.tv_nsec;
 		to->di_flags2 = from->di_flags2;
 		to->di_cowextsize = from->di_cowextsize;
+		if (xfs_sb_version_haswideextcnt(sbp)) {
+			to->di_nextents_hi
+				= xfs_ifork_nextents(&ip->i_df) >> 32;
+			to->di_anextents_hi
+				= xfs_ifork_nextents(ip->i_afp) >> 16;
+		}
+
 		to->di_ino = ip->i_ino;
 		to->di_lsn = lsn;
 		memset(to->di_pad2, 0, sizeof(to->di_pad2));
diff --git a/fs/xfs/xfs_inode_item_recover.c b/fs/xfs/xfs_inode_item_recover.c
index 5e0d291835b3..d2bf9e5b0e24 100644
--- a/fs/xfs/xfs_inode_item_recover.c
+++ b/fs/xfs/xfs_inode_item_recover.c
@@ -126,6 +126,8 @@ xlog_recover_inode_commit_pass2(
 	struct xfs_mount		*mp = log->l_mp;
 	struct xfs_buf			*bp;
 	struct xfs_dinode		*dip;
+	xfs_extnum_t                    nextents;
+	xfs_aextnum_t                   anextents;
 	int				len;
 	char				*src;
 	char				*dest;
@@ -256,16 +258,24 @@ xlog_recover_inode_commit_pass2(
 			goto out_release;
 		}
 	}
-	if (unlikely(ldip->di_nextents + ldip->di_anextents > ldip->di_nblocks)){
+
+	nextents = ldip->di_nextents_lo;
+	if (xfs_sb_version_haswideextcnt(&mp->m_sb))
+		nextents |= ((xfs_extnum_t)(ldip->di_nextents_hi) << 32);
+
+	anextents = ldip->di_anextents_lo;
+	if (xfs_sb_version_haswideextcnt(&mp->m_sb))
+		anextents |= ((xfs_aextnum_t)(ldip->di_anextents_hi) << 16);
+
+	if (unlikely(nextents + anextents > ldip->di_nblocks)) {
 		XFS_CORRUPTION_ERROR("xlog_recover_inode_pass2(5)",
 				     XFS_ERRLEVEL_LOW, mp, ldip,
 				     sizeof(*ldip));
 		xfs_alert(mp,
 	"%s: Bad inode log record, rec ptr "PTR_FMT", dino ptr "PTR_FMT", "
-	"dino bp "PTR_FMT", ino %Ld, total extents = %d, nblocks = %Ld",
+	"dino bp "PTR_FMT", ino %Ld, total extents = %llu, nblocks = %Ld",
 			__func__, item, dip, bp, in_f->ilf_ino,
-			ldip->di_nextents + ldip->di_anextents,
-			ldip->di_nblocks);
+			nextents + anextents, ldip->di_nblocks);
 		error = -EFSCORRUPTED;
 		goto out_release;
 	}
@@ -293,7 +303,7 @@ xlog_recover_inode_commit_pass2(
 	}
 
 	/* recover the log dinode inode into the on disk inode */
-	xfs_log_dinode_to_disk(ldip, dip);
+	xfs_log_dinode_to_disk(mp, ldip, dip);
 
 	fields = in_f->ilf_fields;
 	if (fields & XFS_ILOG_DEV)
