diff mbox series

[01/26] xfs: define the format of rt groups

Message ID 172437088534.60592.14072619855969226822.stgit@frogsfrogsfrogs (mailing list archive)
State Accepted, archived
Headers show
Series [01/26] xfs: define the format of rt groups | expand

Commit Message

Darrick J. Wong Aug. 23, 2024, 12:21 a.m. UTC
From: Darrick J. Wong <djwong@kernel.org>

Define the ondisk format of realtime group metadata, and a superblock
for realtime volumes.  rt supers are protected by a separate rocompat
bit so that we can leave them off if the rt device is zoned.

Add a xfs_sb_version_hasrtgroups so that xfs_repair knows how to zero
the tail of superblocks.

For rt group enabled file systems there is a separate bitmap and summary
file for each group and thus the number of bitmap and summary blocks
needs to be calculated differently.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 fs/xfs/libxfs/xfs_format.h   |   50 +++++++++++++++++++--
 fs/xfs/libxfs/xfs_ondisk.h   |    3 +
 fs/xfs/libxfs/xfs_rtbitmap.c |   20 +++++++-
 fs/xfs/libxfs/xfs_rtgroup.c  |   82 ++++++++++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_sb.c       |  102 +++++++++++++++++++++++++++++++++++++-----
 fs/xfs/libxfs/xfs_shared.h   |    1 
 fs/xfs/xfs_mount.h           |    6 ++
 fs/xfs/xfs_rtalloc.c         |   30 +++++++++++-
 8 files changed, 268 insertions(+), 26 deletions(-)

Comments

Christoph Hellwig Aug. 23, 2024, 5:11 a.m. UTC | #1
On Thu, Aug 22, 2024 at 05:21:25PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> Define the ondisk format of realtime group metadata, and a superblock
> for realtime volumes.  rt supers are protected by a separate rocompat
> bit so that we can leave them off if the rt device is zoned.

We actually killed the flag again and just kept the separate helper
to check for it.

> Add a xfs_sb_version_hasrtgroups so that xfs_repair knows how to zero
> the tail of superblocks.

.. and merged the rtgroup and metadir flags, so while this helper
still exists (and will get lots of use to make the code readable),
that particular use case is gone now.

> -#define XFS_SB_FEAT_RO_COMPAT_FINOBT   (1 << 0)		/* free inode btree */
> -#define XFS_SB_FEAT_RO_COMPAT_RMAPBT   (1 << 1)		/* reverse map btree */
> -#define XFS_SB_FEAT_RO_COMPAT_REFLINK  (1 << 2)		/* reflinked files */
> -#define XFS_SB_FEAT_RO_COMPAT_INOBTCNT (1 << 3)		/* inobt block counts */
> +#define XFS_SB_FEAT_RO_COMPAT_FINOBT	(1 << 0)  /* free inode btree */
> +#define XFS_SB_FEAT_RO_COMPAT_RMAPBT	(1 << 1)  /* reverse map btree */
> +#define XFS_SB_FEAT_RO_COMPAT_REFLINK	(1 << 2)  /* reflinked files */
> +#define XFS_SB_FEAT_RO_COMPAT_INOBTCNT	(1 << 3)  /* inobt block counts */

That also means the above is just a spurious unrelated cleanup now.
Still useful, but maybe it should go into a sepaarate patch?  Or just
don't bother.  Btw, one day we should clearly mark all our on-disk
bitmaps as unsigned.

> +	if (xfs_has_rtgroups(nmp))
> +		nmp->m_sb.sb_rgcount =
> +			howmany_64(nmp->m_sb.sb_rextents, nmp->m_sb.sb_rgextents);

		nmp->m_sb.sb_rgcount = howmany_64(nmp->m_sb.sb_rextents,
						nmp->m_sb.sb_rgextents);

to avoid the overly long line.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
Darrick J. Wong Aug. 23, 2024, 6:12 p.m. UTC | #2
On Thu, Aug 22, 2024 at 10:11:04PM -0700, Christoph Hellwig wrote:
> On Thu, Aug 22, 2024 at 05:21:25PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > Define the ondisk format of realtime group metadata, and a superblock
> > for realtime volumes.  rt supers are protected by a separate rocompat
> > bit so that we can leave them off if the rt device is zoned.
> 
> We actually killed the flag again and just kept the separate helper
> to check for it.
> 
> > Add a xfs_sb_version_hasrtgroups so that xfs_repair knows how to zero
> > the tail of superblocks.
> 
> .. and merged the rtgroup and metadir flags, so while this helper
> still exists (and will get lots of use to make the code readable),
> that particular use case is gone now.

I'll just delete this sentence since xfs_sb_version_hasmetadir is in
another patch anyway.

> > -#define XFS_SB_FEAT_RO_COMPAT_FINOBT   (1 << 0)		/* free inode btree */
> > -#define XFS_SB_FEAT_RO_COMPAT_RMAPBT   (1 << 1)		/* reverse map btree */
> > -#define XFS_SB_FEAT_RO_COMPAT_REFLINK  (1 << 2)		/* reflinked files */
> > -#define XFS_SB_FEAT_RO_COMPAT_INOBTCNT (1 << 3)		/* inobt block counts */
> > +#define XFS_SB_FEAT_RO_COMPAT_FINOBT	(1 << 0)  /* free inode btree */
> > +#define XFS_SB_FEAT_RO_COMPAT_RMAPBT	(1 << 1)  /* reverse map btree */
> > +#define XFS_SB_FEAT_RO_COMPAT_REFLINK	(1 << 2)  /* reflinked files */
> > +#define XFS_SB_FEAT_RO_COMPAT_INOBTCNT	(1 << 3)  /* inobt block counts */
> 
> That also means the above is just a spurious unrelated cleanup now.
> Still useful, but maybe it should go into a sepaarate patch?  Or just
> don't bother.  Btw, one day we should clearly mark all our on-disk
> bitmaps as unsigned.

Eh, I'll drop it and make the next new rocompat feature do it.

> > +	if (xfs_has_rtgroups(nmp))
> > +		nmp->m_sb.sb_rgcount =
> > +			howmany_64(nmp->m_sb.sb_rextents, nmp->m_sb.sb_rgextents);
> 
> 		nmp->m_sb.sb_rgcount = howmany_64(nmp->m_sb.sb_rextents,
> 						nmp->m_sb.sb_rgextents);

Done.

> to avoid the overly long line.
> 
> Otherwise looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks!

--D
diff mbox series

Patch

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index fa5cfc8265d92..9e351b19bd86e 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -265,8 +265,15 @@  struct xfs_dsb {
 	uuid_t		sb_meta_uuid;	/* metadata file system unique id */
 
 	__be64		sb_metadirino;	/* metadata directory tree root */
+	__be32		sb_rgcount;	/* # of realtime groups */
+	__be32		sb_rgextents;	/* size of rtgroup in rtx */
 
-	/* must be padded to 64 bit alignment */
+	/*
+	 * The size of this structure must be padded to 64 bit alignment.
+	 *
+	 * NOTE: Don't forget to update secondary_sb_whack in xfs_repair when
+	 * adding new fields here.
+	 */
 };
 
 #define XFS_SB_CRC_OFF		offsetof(struct xfs_dsb, sb_crc)
@@ -355,10 +362,10 @@  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_RMAPBT   (1 << 1)		/* reverse map btree */
-#define XFS_SB_FEAT_RO_COMPAT_REFLINK  (1 << 2)		/* reflinked files */
-#define XFS_SB_FEAT_RO_COMPAT_INOBTCNT (1 << 3)		/* inobt block counts */
+#define XFS_SB_FEAT_RO_COMPAT_FINOBT	(1 << 0)  /* free inode btree */
+#define XFS_SB_FEAT_RO_COMPAT_RMAPBT	(1 << 1)  /* reverse map btree */
+#define XFS_SB_FEAT_RO_COMPAT_REFLINK	(1 << 2)  /* reflinked files */
+#define XFS_SB_FEAT_RO_COMPAT_INOBTCNT	(1 << 3)  /* inobt block counts */
 #define XFS_SB_FEAT_RO_COMPAT_ALL \
 		(XFS_SB_FEAT_RO_COMPAT_FINOBT | \
 		 XFS_SB_FEAT_RO_COMPAT_RMAPBT | \
@@ -722,6 +729,39 @@  union xfs_suminfo_raw {
 	__u32		old;
 };
 
+/*
+ * Realtime allocation groups break the rt section into multiple pieces that
+ * could be locked independently.  Realtime block group numbers are 32-bit
+ * quantities.  Block numbers within a group are also 32-bit quantities, but
+ * the upper bit must never be set.  rtgroup 0 might have a superblock in it,
+ * so the minimum size of an rtgroup is 2 rtx.
+ */
+#define XFS_MAX_RGBLOCKS	((xfs_rgblock_t)(1U << 31) - 1)
+#define XFS_MIN_RGEXTENTS	((xfs_rtxlen_t)2)
+#define XFS_MAX_RGNUMBER	((xfs_rgnumber_t)(-1U))
+
+#define XFS_RTSB_MAGIC	0x46726F67	/* 'Frog' */
+
+/*
+ * Realtime superblock - on disk version.  Must be padded to 64 bit alignment.
+ * The first block of the realtime volume contains this superblock.
+ */
+struct xfs_rtsb {
+	__be32		rsb_magicnum;	/* magic number == XFS_RTSB_MAGIC */
+	__le32		rsb_crc;	/* superblock crc */
+
+	__be32		rsb_pad;	/* zero */
+	unsigned char	rsb_fname[XFSLABEL_MAX]; /* file system name */
+
+	uuid_t		rsb_uuid;	/* user-visible file system unique id */
+	uuid_t		rsb_meta_uuid;	/* metadata file system unique id */
+
+	/* must be padded to 64 bit alignment */
+};
+
+#define XFS_RTSB_CRC_OFF	offsetof(struct xfs_rtsb, rsb_crc)
+#define XFS_RTSB_DADDR		((xfs_daddr_t)0) /* daddr in rt section */
+
 /*
  * XFS Timestamps
  * ==============
diff --git a/fs/xfs/libxfs/xfs_ondisk.h b/fs/xfs/libxfs/xfs_ondisk.h
index 8bca86e350fdc..38b314113d8f2 100644
--- a/fs/xfs/libxfs/xfs_ondisk.h
+++ b/fs/xfs/libxfs/xfs_ondisk.h
@@ -37,7 +37,7 @@  xfs_check_ondisk_structs(void)
 	XFS_CHECK_STRUCT_SIZE(struct xfs_dinode,		176);
 	XFS_CHECK_STRUCT_SIZE(struct xfs_disk_dquot,		104);
 	XFS_CHECK_STRUCT_SIZE(struct xfs_dqblk,			136);
-	XFS_CHECK_STRUCT_SIZE(struct xfs_dsb,			272);
+	XFS_CHECK_STRUCT_SIZE(struct xfs_dsb,			280);
 	XFS_CHECK_STRUCT_SIZE(struct xfs_dsymlink_hdr,		56);
 	XFS_CHECK_STRUCT_SIZE(struct xfs_inobt_key,		4);
 	XFS_CHECK_STRUCT_SIZE(struct xfs_inobt_rec,		16);
@@ -53,6 +53,7 @@  xfs_check_ondisk_structs(void)
 	XFS_CHECK_STRUCT_SIZE(xfs_inobt_ptr_t,			4);
 	XFS_CHECK_STRUCT_SIZE(xfs_refcount_ptr_t,		4);
 	XFS_CHECK_STRUCT_SIZE(xfs_rmap_ptr_t,			4);
+	XFS_CHECK_STRUCT_SIZE(struct xfs_rtsb,			56);
 
 	/* dir/attr trees */
 	XFS_CHECK_STRUCT_SIZE(struct xfs_attr3_leaf_hdr,	80);
diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
index 7a848cacd561d..330acf1ab39f8 100644
--- a/fs/xfs/libxfs/xfs_rtbitmap.c
+++ b/fs/xfs/libxfs/xfs_rtbitmap.c
@@ -1157,6 +1157,21 @@  xfs_rtbitmap_blockcount_len(
 	return howmany_64(rtextents, NBBY * mp->m_sb.sb_blocksize);
 }
 
+/* How many rt extents does each rtbitmap file track? */
+static inline xfs_rtbxlen_t
+xfs_rtbitmap_bitcount(
+	struct xfs_mount	*mp)
+{
+	if (!mp->m_sb.sb_rextents)
+		return 0;
+
+	/* rtgroup size can be nonzero even if rextents is zero */
+	if (xfs_has_rtgroups(mp))
+		return mp->m_sb.sb_rgextents;
+
+	return mp->m_sb.sb_rextents;
+}
+
 /*
  * Compute the number of rtbitmap blocks used for a given file system.
  */
@@ -1164,7 +1179,7 @@  xfs_filblks_t
 xfs_rtbitmap_blockcount(
 	struct xfs_mount	*mp)
 {
-	return xfs_rtbitmap_blockcount_len(mp, mp->m_sb.sb_rextents);
+	return xfs_rtbitmap_blockcount_len(mp, xfs_rtbitmap_bitcount(mp));
 }
 
 /*
@@ -1178,8 +1193,7 @@  xfs_rtsummary_blockcount(
 {
 	unsigned long long	rsumwords;
 
-	*rsumlevels = xfs_compute_rextslog(mp->m_sb.sb_rextents) + 1;
-
+	*rsumlevels = xfs_compute_rextslog(xfs_rtbitmap_bitcount(mp)) + 1;
 	rsumwords = xfs_rtbitmap_blockcount(mp) * (*rsumlevels);
 	return XFS_B_TO_FSB(mp, rsumwords << XFS_WORDLOG);
 }
diff --git a/fs/xfs/libxfs/xfs_rtgroup.c b/fs/xfs/libxfs/xfs_rtgroup.c
index 4618caf344efd..2a8d5561da9d0 100644
--- a/fs/xfs/libxfs/xfs_rtgroup.c
+++ b/fs/xfs/libxfs/xfs_rtgroup.c
@@ -28,6 +28,7 @@ 
 #include "xfs_trace.h"
 #include "xfs_inode.h"
 #include "xfs_icache.h"
+#include "xfs_buf_item.h"
 #include "xfs_rtgroup.h"
 #include "xfs_rtbitmap.h"
 #include "xfs_metafile.h"
@@ -527,3 +528,84 @@  xfs_rtginode_load_parent(
 	return xfs_metadir_load(tp, mp->m_metadirip, "rtgroups",
 			XFS_METAFILE_DIR, &mp->m_rtdirip);
 }
+
+/* Check superblock fields for a read or a write. */
+static xfs_failaddr_t
+xfs_rtsb_verify_common(
+	struct xfs_buf		*bp)
+{
+	struct xfs_rtsb		*rsb = bp->b_addr;
+
+	if (!xfs_verify_magic(bp, rsb->rsb_magicnum))
+		return __this_address;
+	if (rsb->rsb_pad)
+		return __this_address;
+
+	/* Everything to the end of the fs block must be zero */
+	if (memchr_inv(rsb + 1, 0, BBTOB(bp->b_length) - sizeof(*rsb)))
+		return __this_address;
+
+	return NULL;
+}
+
+/* Check superblock fields for a read or revalidation. */
+static inline xfs_failaddr_t
+xfs_rtsb_verify_all(
+	struct xfs_buf		*bp)
+{
+	struct xfs_rtsb		*rsb = bp->b_addr;
+	struct xfs_mount	*mp = bp->b_mount;
+	xfs_failaddr_t		fa;
+
+	fa = xfs_rtsb_verify_common(bp);
+	if (fa)
+		return fa;
+
+	if (memcmp(&rsb->rsb_fname, &mp->m_sb.sb_fname, XFSLABEL_MAX))
+		return __this_address;
+	if (!uuid_equal(&rsb->rsb_uuid, &mp->m_sb.sb_uuid))
+		return __this_address;
+	if (!uuid_equal(&rsb->rsb_meta_uuid, &mp->m_sb.sb_meta_uuid))
+		return  __this_address;
+
+	return NULL;
+}
+
+static void
+xfs_rtsb_read_verify(
+	struct xfs_buf		*bp)
+{
+	xfs_failaddr_t		fa;
+
+	if (!xfs_buf_verify_cksum(bp, XFS_RTSB_CRC_OFF)) {
+		xfs_verifier_error(bp, -EFSBADCRC, __this_address);
+		return;
+	}
+
+	fa = xfs_rtsb_verify_all(bp);
+	if (fa)
+		xfs_verifier_error(bp, -EFSCORRUPTED, fa);
+}
+
+static void
+xfs_rtsb_write_verify(
+	struct xfs_buf		*bp)
+{
+	xfs_failaddr_t		fa;
+
+	fa = xfs_rtsb_verify_common(bp);
+	if (fa) {
+		xfs_verifier_error(bp, -EFSCORRUPTED, fa);
+		return;
+	}
+
+	xfs_buf_update_cksum(bp, XFS_RTSB_CRC_OFF);
+}
+
+const struct xfs_buf_ops xfs_rtsb_buf_ops = {
+	.name		= "xfs_rtsb",
+	.magic		= { 0, cpu_to_be32(XFS_RTSB_MAGIC) },
+	.verify_read	= xfs_rtsb_read_verify,
+	.verify_write	= xfs_rtsb_write_verify,
+	.verify_struct	= xfs_rtsb_verify_all,
+};
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index f1cdffb2f3392..e33afd8f3e256 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -234,11 +234,21 @@  xfs_validate_sb_read(
 	return 0;
 }
 
+/* Return the number of extents covered by a single rt bitmap file */
+static xfs_rtbxlen_t
+xfs_extents_per_rbm(
+	struct xfs_sb		*sbp)
+{
+	if (xfs_sb_version_hasmetadir(sbp))
+		return sbp->sb_rgextents;
+	return sbp->sb_rextents;
+}
+
 static uint64_t
-xfs_sb_calc_rbmblocks(
+xfs_expected_rbmblocks(
 	struct xfs_sb		*sbp)
 {
-	return howmany_64(sbp->sb_rextents, NBBY * sbp->sb_blocksize);
+	return howmany_64(xfs_extents_per_rbm(sbp), NBBY * sbp->sb_blocksize);
 }
 
 /* Validate the realtime geometry */
@@ -260,7 +270,7 @@  xfs_validate_rt_geometry(
 	if (sbp->sb_rextents == 0 ||
 	    sbp->sb_rextents != div_u64(sbp->sb_rblocks, sbp->sb_rextsize) ||
 	    sbp->sb_rextslog != xfs_compute_rextslog(sbp->sb_rextents) ||
-	    sbp->sb_rbmblocks != xfs_sb_calc_rbmblocks(sbp))
+	    sbp->sb_rbmblocks != xfs_expected_rbmblocks(sbp))
 		return false;
 
 	return true;
@@ -341,6 +351,62 @@  xfs_validate_sb_write(
 	return 0;
 }
 
+static int
+xfs_validate_sb_rtgroups(
+	struct xfs_mount	*mp,
+	struct xfs_sb		*sbp)
+{
+	uint64_t		groups;
+
+	if (!sbp->sb_rextents)
+		return 0;
+
+	if (sbp->sb_rextsize == 0) {
+		xfs_warn(mp,
+"Realtime extent size must not be zero.");
+		return -EINVAL;
+	}
+
+	if (sbp->sb_rgextents > XFS_MAX_RGBLOCKS / sbp->sb_rextsize) {
+		xfs_warn(mp,
+"Realtime group size (%u) must be less than %u rt extents.",
+				sbp->sb_rgextents,
+				XFS_MAX_RGBLOCKS / sbp->sb_rextsize);
+		return -EINVAL;
+	}
+
+	if (sbp->sb_rgextents < XFS_MIN_RGEXTENTS) {
+		xfs_warn(mp,
+"Realtime group size (%u) must be at least %u rt extents.",
+				sbp->sb_rgextents, XFS_MIN_RGEXTENTS);
+		return -EINVAL;
+	}
+
+	if (sbp->sb_rgcount > XFS_MAX_RGNUMBER) {
+		xfs_warn(mp,
+"Realtime groups (%u) must be less than %u.",
+				sbp->sb_rgcount, XFS_MAX_RGNUMBER);
+		return -EINVAL;
+	}
+
+	groups = howmany_64(sbp->sb_rextents, sbp->sb_rgextents);
+	if (groups != sbp->sb_rgcount) {
+		xfs_warn(mp,
+"Realtime groups (%u) do not cover the entire rt section; need (%llu) groups.",
+				sbp->sb_rgcount, groups);
+		return -EINVAL;
+	}
+
+	/* Exchange-range is required for fsr to work on realtime files */
+	if (!(sbp->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_EXCHRANGE)) {
+		xfs_warn(mp,
+"Realtime groups feature requires exchange-range support.");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 /* Check the validity of the SB. */
 STATIC int
 xfs_validate_sb_common(
@@ -352,6 +418,7 @@  xfs_validate_sb_common(
 	uint32_t		agcount = 0;
 	uint32_t		rem;
 	bool			has_dalign;
+	int			error;
 
 	if (!xfs_verify_magic(bp, dsb->sb_magicnum)) {
 		xfs_warn(mp,
@@ -401,6 +468,12 @@  xfs_validate_sb_common(
 				return -EINVAL;
 			}
 		}
+
+		if (xfs_sb_version_hasmetadir(sbp))  {
+			error = xfs_validate_sb_rtgroups(mp, sbp);
+			if (error)
+				return error;
+		}
 	} else if (sbp->sb_qflags & (XFS_PQUOTA_ENFD | XFS_GQUOTA_ENFD |
 				XFS_PQUOTA_CHKD | XFS_GQUOTA_CHKD)) {
 			xfs_notice(mp,
@@ -692,13 +765,15 @@  __xfs_sb_from_disk(
 	if (convert_xquota)
 		xfs_sb_quota_from_disk(to);
 
-	if (to->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_METADIR)
+	if (to->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_METADIR) {
 		to->sb_metadirino = be64_to_cpu(from->sb_metadirino);
-	else
+		to->sb_rgcount = be32_to_cpu(from->sb_rgcount);
+		to->sb_rgextents = be32_to_cpu(from->sb_rgextents);
+	} else {
 		to->sb_metadirino = NULLFSINO;
-
-	to->sb_rgcount = 1;
-	to->sb_rgextents = 0;
+		to->sb_rgcount = 1;
+		to->sb_rgextents = 0;
+	}
 }
 
 void
@@ -847,8 +922,11 @@  xfs_sb_to_disk(
 	if (from->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_META_UUID)
 		uuid_copy(&to->sb_meta_uuid, &from->sb_meta_uuid);
 
-	if (from->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_METADIR)
+	if (from->sb_features_incompat & XFS_SB_FEAT_INCOMPAT_METADIR) {
 		to->sb_metadirino = cpu_to_be64(from->sb_metadirino);
+		to->sb_rgcount = cpu_to_be32(from->sb_rgcount);
+		to->sb_rgextents = cpu_to_be32(from->sb_rgextents);
+	}
 }
 
 /*
@@ -986,9 +1064,9 @@  xfs_mount_sb_set_rextsize(
 	mp->m_rtxblklog = log2_if_power2(sbp->sb_rextsize);
 	mp->m_rtxblkmask = mask64_if_power2(sbp->sb_rextsize);
 
-	mp->m_rgblocks = 0;
-	mp->m_rgblklog = 0;
-	mp->m_rgblkmask = 0;
+	mp->m_rgblocks = sbp->sb_rgextents * sbp->sb_rextsize;
+	mp->m_rgblklog = log2_if_power2(mp->m_rgblocks);
+	mp->m_rgblkmask = mask64_if_power2(mp->m_rgblocks);
 }
 
 /*
diff --git a/fs/xfs/libxfs/xfs_shared.h b/fs/xfs/libxfs/xfs_shared.h
index 2f7413afbf46c..0343926d2a6b4 100644
--- a/fs/xfs/libxfs/xfs_shared.h
+++ b/fs/xfs/libxfs/xfs_shared.h
@@ -39,6 +39,7 @@  extern const struct xfs_buf_ops xfs_inode_buf_ra_ops;
 extern const struct xfs_buf_ops xfs_refcountbt_buf_ops;
 extern const struct xfs_buf_ops xfs_rmapbt_buf_ops;
 extern const struct xfs_buf_ops xfs_rtbuf_ops;
+extern const struct xfs_buf_ops xfs_rtsb_buf_ops;
 extern const struct xfs_buf_ops xfs_sb_buf_ops;
 extern const struct xfs_buf_ops xfs_sb_quiet_buf_ops;
 extern const struct xfs_buf_ops xfs_symlink_buf_ops;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 137fb5f88307b..6d49893fc91c7 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -355,12 +355,14 @@  __XFS_HAS_FEAT(metadir, METADIR)
 
 static inline bool xfs_has_rtgroups(struct xfs_mount *mp)
 {
-	return false;
+	/* all metadir file systems also allow rtgroups */
+	return xfs_has_metadir(mp);
 }
 
 static inline bool xfs_has_rtsb(struct xfs_mount *mp)
 {
-	return false;
+	/* all rtgroups filesystems with an rt section have an rtsb */
+	return xfs_has_rtgroups(mp) && xfs_has_realtime(mp);
 }
 
 /*
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 308049f2fb79d..b2c0c3fe64a11 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -751,6 +751,11 @@  xfs_growfs_rt_alloc_fake_mount(
 	nmp->m_sb.sb_rextents = xfs_blen_to_rtbxlen(nmp, nmp->m_sb.sb_rblocks);
 	nmp->m_sb.sb_rbmblocks = xfs_rtbitmap_blockcount(nmp);
 	nmp->m_sb.sb_rextslog = xfs_compute_rextslog(nmp->m_sb.sb_rextents);
+	if (xfs_has_rtgroups(nmp))
+		nmp->m_sb.sb_rgcount =
+			howmany_64(nmp->m_sb.sb_rextents, nmp->m_sb.sb_rgextents);
+	else
+		nmp->m_sb.sb_rgcount = 1;
 	nmp->m_rsumblocks = xfs_rtsummary_blockcount(nmp, &nmp->m_rsumlevels);
 
 	if (rblocks > 0)
@@ -761,6 +766,26 @@  xfs_growfs_rt_alloc_fake_mount(
 	return nmp;
 }
 
+static xfs_rfsblock_t
+xfs_growfs_rt_nrblocks(
+	struct xfs_rtgroup	*rtg,
+	xfs_rfsblock_t		nrblocks,
+	xfs_agblock_t		rextsize,
+	xfs_fileoff_t		bmbno)
+{
+	struct xfs_mount	*mp = rtg->rtg_mount;
+	xfs_rfsblock_t		step;
+
+	step = (bmbno + 1) * NBBY * mp->m_sb.sb_blocksize * rextsize;
+	if (xfs_has_rtgroups(mp)) {
+		xfs_rfsblock_t	rgblocks = mp->m_sb.sb_rgextents * rextsize;
+
+		step = min(rgblocks, step) + rgblocks * rtg->rtg_rgno;
+	}
+
+	return min(nrblocks, step);
+}
+
 static int
 xfs_growfs_rt_bmblock(
 	struct xfs_rtgroup	*rtg,
@@ -779,16 +804,15 @@  xfs_growfs_rt_bmblock(
 		.rtg		= rtg,
 	};
 	struct xfs_mount	*nmp;
-	xfs_rfsblock_t		nrblocks_step;
 	xfs_rtbxlen_t		freed_rtx;
 	int			error;
 
 	/*
 	 * Calculate new sb and mount fields for this round.
 	 */
-	nrblocks_step = (bmbno + 1) * NBBY * mp->m_sb.sb_blocksize * rextsize;
 	nmp = nargs.mp = xfs_growfs_rt_alloc_fake_mount(mp,
-			min(nrblocks, nrblocks_step), rextsize);
+			xfs_growfs_rt_nrblocks(rtg, nrblocks, rextsize, bmbno),
+			rextsize);
 	if (!nmp)
 		return -ENOMEM;