1 files changed, 697 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_rtgroup.c b/fs/xfs/libxfs/xfs_rtgroup.c
new file mode 100644
index 000000000000..e74bb059f24f
--- /dev/null
+++ b/fs/xfs/libxfs/xfs_rtgroup.c
@@ -0,0 +1,697 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2022-2024 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_bit.h"
+#include "xfs_sb.h"
+#include "xfs_mount.h"
+#include "xfs_btree.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_rmap_btree.h"
+#include "xfs_alloc.h"
+#include "xfs_ialloc.h"
+#include "xfs_rmap.h"
+#include "xfs_ag.h"
+#include "xfs_ag_resv.h"
+#include "xfs_health.h"
+#include "xfs_error.h"
+#include "xfs_bmap.h"
+#include "xfs_defer.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#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"
+#include "xfs_metadir.h"
+
+/* Find the first usable fsblock in this rtgroup. */
+static inline uint32_t
+xfs_rtgroup_min_block(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		rgno)
+{
+	if (xfs_has_rtsb(mp) && rgno == 0)
+		return mp->m_sb.sb_rextsize;
+
+	return 0;
+}
+
+/* Precompute this group's geometry */
+void
+xfs_rtgroup_calc_geometry(
+	struct xfs_mount	*mp,
+	struct xfs_rtgroup	*rtg,
+	xfs_rgnumber_t		rgno,
+	xfs_rgnumber_t		rgcount,
+	xfs_rtbxlen_t		rextents)
+{
+	rtg->rtg_extents = __xfs_rtgroup_extents(mp, rgno, rgcount, rextents);
+	rtg_group(rtg)->xg_block_count = rtg->rtg_extents * mp->m_sb.sb_rextsize;
+	rtg_group(rtg)->xg_min_gbno = xfs_rtgroup_min_block(mp, rgno);
+}
+
+int
+xfs_rtgroup_alloc(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		rgno,
+	xfs_rgnumber_t		rgcount,
+	xfs_rtbxlen_t		rextents)
+{
+	struct xfs_rtgroup	*rtg;
+	int			error;
+
+	rtg = kzalloc(sizeof(struct xfs_rtgroup), GFP_KERNEL);
+	if (!rtg)
+		return -ENOMEM;
+
+	xfs_rtgroup_calc_geometry(mp, rtg, rgno, rgcount, rextents);
+
+	error = xfs_group_insert(mp, rtg_group(rtg), rgno, XG_TYPE_RTG);
+	if (error)
+		goto out_free_rtg;
+	return 0;
+
+out_free_rtg:
+	kfree(rtg);
+	return error;
+}
+
+void
+xfs_rtgroup_free(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		rgno)
+{
+	xfs_group_free(mp, rgno, XG_TYPE_RTG, NULL);
+}
+
+/* Free a range of incore rtgroup objects. */
+void
+xfs_free_rtgroups(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		first_rgno,
+	xfs_rgnumber_t		end_rgno)
+{
+	xfs_rgnumber_t		rgno;
+
+	for (rgno = first_rgno; rgno < end_rgno; rgno++)
+		xfs_rtgroup_free(mp, rgno);
+}
+
+/* Initialize some range of incore rtgroup objects. */
+int
+xfs_initialize_rtgroups(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		first_rgno,
+	xfs_rgnumber_t		end_rgno,
+	xfs_rtbxlen_t		rextents)
+{
+	xfs_rgnumber_t		index;
+	int			error;
+
+	if (first_rgno >= end_rgno)
+		return 0;
+
+	for (index = first_rgno; index < end_rgno; index++) {
+		error = xfs_rtgroup_alloc(mp, index, end_rgno, rextents);
+		if (error)
+			goto out_unwind_new_rtgs;
+	}
+
+	return 0;
+
+out_unwind_new_rtgs:
+	xfs_free_rtgroups(mp, first_rgno, index);
+	return error;
+}
+
+/* Compute the number of rt extents in this realtime group. */
+xfs_rtxnum_t
+__xfs_rtgroup_extents(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		rgno,
+	xfs_rgnumber_t		rgcount,
+	xfs_rtbxlen_t		rextents)
+{
+	ASSERT(rgno < rgcount);
+	if (rgno == rgcount - 1)
+		return rextents - ((xfs_rtxnum_t)rgno * mp->m_sb.sb_rgextents);
+
+	ASSERT(xfs_has_rtgroups(mp));
+	return mp->m_sb.sb_rgextents;
+}
+
+xfs_rtxnum_t
+xfs_rtgroup_extents(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		rgno)
+{
+	return __xfs_rtgroup_extents(mp, rgno, mp->m_sb.sb_rgcount,
+			mp->m_sb.sb_rextents);
+}
+
+/*
+ * Update the rt extent count of the previous tail rtgroup if it changed during
+ * recovery (i.e. recovery of a growfs).
+ */
+int
+xfs_update_last_rtgroup_size(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		prev_rgcount)
+{
+	struct xfs_rtgroup	*rtg;
+
+	ASSERT(prev_rgcount > 0);
+
+	rtg = xfs_rtgroup_grab(mp, prev_rgcount - 1);
+	if (!rtg)
+		return -EFSCORRUPTED;
+	rtg->rtg_extents = __xfs_rtgroup_extents(mp, prev_rgcount - 1,
+			mp->m_sb.sb_rgcount, mp->m_sb.sb_rextents);
+	rtg_group(rtg)->xg_block_count = rtg->rtg_extents * mp->m_sb.sb_rextsize;
+	xfs_rtgroup_rele(rtg);
+	return 0;
+}
+
+/* Lock metadata inodes associated with this rt group. */
+void
+xfs_rtgroup_lock(
+	struct xfs_rtgroup	*rtg,
+	unsigned int		rtglock_flags)
+{
+	ASSERT(!(rtglock_flags & ~XFS_RTGLOCK_ALL_FLAGS));
+	ASSERT(!(rtglock_flags & XFS_RTGLOCK_BITMAP_SHARED) ||
+	       !(rtglock_flags & XFS_RTGLOCK_BITMAP));
+
+	if (rtglock_flags & XFS_RTGLOCK_BITMAP) {
+		/*
+		 * Lock both realtime free space metadata inodes for a freespace
+		 * update.
+		 */
+		xfs_ilock(rtg->rtg_inodes[XFS_RTGI_BITMAP], XFS_ILOCK_EXCL);
+		xfs_ilock(rtg->rtg_inodes[XFS_RTGI_SUMMARY], XFS_ILOCK_EXCL);
+	} else if (rtglock_flags & XFS_RTGLOCK_BITMAP_SHARED) {
+		xfs_ilock(rtg->rtg_inodes[XFS_RTGI_BITMAP], XFS_ILOCK_SHARED);
+	}
+}
+
+/* Unlock metadata inodes associated with this rt group. */
+void
+xfs_rtgroup_unlock(
+	struct xfs_rtgroup	*rtg,
+	unsigned int		rtglock_flags)
+{
+	ASSERT(!(rtglock_flags & ~XFS_RTGLOCK_ALL_FLAGS));
+	ASSERT(!(rtglock_flags & XFS_RTGLOCK_BITMAP_SHARED) ||
+	       !(rtglock_flags & XFS_RTGLOCK_BITMAP));
+
+	if (rtglock_flags & XFS_RTGLOCK_BITMAP) {
+		xfs_iunlock(rtg->rtg_inodes[XFS_RTGI_SUMMARY], XFS_ILOCK_EXCL);
+		xfs_iunlock(rtg->rtg_inodes[XFS_RTGI_BITMAP], XFS_ILOCK_EXCL);
+	} else if (rtglock_flags & XFS_RTGLOCK_BITMAP_SHARED) {
+		xfs_iunlock(rtg->rtg_inodes[XFS_RTGI_BITMAP], XFS_ILOCK_SHARED);
+	}
+}
+
+/*
+ * Join realtime group metadata inodes to the transaction.  The ILOCKs will be
+ * released on transaction commit.
+ */
+void
+xfs_rtgroup_trans_join(
+	struct xfs_trans	*tp,
+	struct xfs_rtgroup	*rtg,
+	unsigned int		rtglock_flags)
+{
+	ASSERT(!(rtglock_flags & ~XFS_RTGLOCK_ALL_FLAGS));
+	ASSERT(!(rtglock_flags & XFS_RTGLOCK_BITMAP_SHARED));
+
+	if (rtglock_flags & XFS_RTGLOCK_BITMAP) {
+		xfs_trans_ijoin(tp, rtg->rtg_inodes[XFS_RTGI_BITMAP],
+				XFS_ILOCK_EXCL);
+		xfs_trans_ijoin(tp, rtg->rtg_inodes[XFS_RTGI_SUMMARY],
+				XFS_ILOCK_EXCL);
+	}
+}
+
+/* Retrieve rt group geometry. */
+int
+xfs_rtgroup_get_geometry(
+	struct xfs_rtgroup	*rtg,
+	struct xfs_rtgroup_geometry *rgeo)
+{
+	/* Fill out form. */
+	memset(rgeo, 0, sizeof(*rgeo));
+	rgeo->rg_number = rtg_rgno(rtg);
+	rgeo->rg_length = rtg_group(rtg)->xg_block_count;
+	xfs_rtgroup_geom_health(rtg, rgeo);
+	return 0;
+}
+
+#ifdef CONFIG_PROVE_LOCKING
+static struct lock_class_key xfs_rtginode_lock_class;
+
+static int
+xfs_rtginode_ilock_cmp_fn(
+	const struct lockdep_map	*m1,
+	const struct lockdep_map	*m2)
+{
+	const struct xfs_inode *ip1 =
+		container_of(m1, struct xfs_inode, i_lock.dep_map);
+	const struct xfs_inode *ip2 =
+		container_of(m2, struct xfs_inode, i_lock.dep_map);
+
+	if (ip1->i_projid < ip2->i_projid)
+		return -1;
+	if (ip1->i_projid > ip2->i_projid)
+		return 1;
+	return 0;
+}
+
+static inline void
+xfs_rtginode_ilock_print_fn(
+	const struct lockdep_map	*m)
+{
+	const struct xfs_inode *ip =
+		container_of(m, struct xfs_inode, i_lock.dep_map);
+
+	printk(KERN_CONT " rgno=%u", ip->i_projid);
+}
+
+/*
+ * Most of the time each of the RTG inode locks are only taken one at a time.
+ * But when committing deferred ops, more than one of a kind can be taken.
+ * However, deferred rt ops will be committed in rgno order so there is no
+ * potential for deadlocks.  The code here is needed to tell lockdep about this
+ * order.
+ */
+static inline void
+xfs_rtginode_lockdep_setup(
+	struct xfs_inode	*ip,
+	xfs_rgnumber_t		rgno,
+	enum xfs_rtg_inodes	type)
+{
+	lockdep_set_class_and_subclass(&ip->i_lock, &xfs_rtginode_lock_class,
+			type);
+	lock_set_cmp_fn(&ip->i_lock, xfs_rtginode_ilock_cmp_fn,
+			xfs_rtginode_ilock_print_fn);
+}
+#else
+#define xfs_rtginode_lockdep_setup(ip, rgno, type)	do { } while (0)
+#endif /* CONFIG_PROVE_LOCKING */
+
+struct xfs_rtginode_ops {
+	const char		*name;	/* short name */
+
+	enum xfs_metafile_type	metafile_type;
+
+	unsigned int		sick;	/* rtgroup sickness flag */
+
+	/* Does the fs have this feature? */
+	bool			(*enabled)(struct xfs_mount *mp);
+
+	/* Create this rtgroup metadata inode and initialize it. */
+	int			(*create)(struct xfs_rtgroup *rtg,
+					  struct xfs_inode *ip,
+					  struct xfs_trans *tp,
+					  bool init);
+};
+
+static const struct xfs_rtginode_ops xfs_rtginode_ops[XFS_RTGI_MAX] = {
+	[XFS_RTGI_BITMAP] = {
+		.name		= "bitmap",
+		.metafile_type	= XFS_METAFILE_RTBITMAP,
+		.sick		= XFS_SICK_RG_BITMAP,
+		.create		= xfs_rtbitmap_create,
+	},
+	[XFS_RTGI_SUMMARY] = {
+		.name		= "summary",
+		.metafile_type	= XFS_METAFILE_RTSUMMARY,
+		.sick		= XFS_SICK_RG_SUMMARY,
+		.create		= xfs_rtsummary_create,
+	},
+};
+
+/* Return the shortname of this rtgroup inode. */
+const char *
+xfs_rtginode_name(
+	enum xfs_rtg_inodes	type)
+{
+	return xfs_rtginode_ops[type].name;
+}
+
+/* Return the metafile type of this rtgroup inode. */
+enum xfs_metafile_type
+xfs_rtginode_metafile_type(
+	enum xfs_rtg_inodes	type)
+{
+	return xfs_rtginode_ops[type].metafile_type;
+}
+
+/* Should this rtgroup inode be present? */
+bool
+xfs_rtginode_enabled(
+	struct xfs_rtgroup	*rtg,
+	enum xfs_rtg_inodes	type)
+{
+	const struct xfs_rtginode_ops *ops = &xfs_rtginode_ops[type];
+
+	if (!ops->enabled)
+		return true;
+	return ops->enabled(rtg_mount(rtg));
+}
+
+/* Mark an rtgroup inode sick */
+void
+xfs_rtginode_mark_sick(
+	struct xfs_rtgroup	*rtg,
+	enum xfs_rtg_inodes	type)
+{
+	const struct xfs_rtginode_ops *ops = &xfs_rtginode_ops[type];
+
+	xfs_group_mark_sick(rtg_group(rtg), ops->sick);
+}
+
+/* Load and existing rtgroup inode into the rtgroup structure. */
+int
+xfs_rtginode_load(
+	struct xfs_rtgroup	*rtg,
+	enum xfs_rtg_inodes	type,
+	struct xfs_trans	*tp)
+{
+	struct xfs_mount	*mp = tp->t_mountp;
+	struct xfs_inode	*ip;
+	const struct xfs_rtginode_ops *ops = &xfs_rtginode_ops[type];
+	int			error;
+
+	if (!xfs_rtginode_enabled(rtg, type))
+		return 0;
+
+	if (!xfs_has_rtgroups(mp)) {
+		xfs_ino_t	ino;
+
+		switch (type) {
+		case XFS_RTGI_BITMAP:
+			ino = mp->m_sb.sb_rbmino;
+			break;
+		case XFS_RTGI_SUMMARY:
+			ino = mp->m_sb.sb_rsumino;
+			break;
+		default:
+			/* None of the other types exist on !rtgroups */
+			return 0;
+		}
+
+		error = xfs_trans_metafile_iget(tp, ino, ops->metafile_type,
+				&ip);
+	} else {
+		const char	*path;
+
+		if (!mp->m_rtdirip) {
+			xfs_fs_mark_sick(mp, XFS_SICK_FS_METADIR);
+			return -EFSCORRUPTED;
+		}
+
+		path = xfs_rtginode_path(rtg_rgno(rtg), type);
+		if (!path)
+			return -ENOMEM;
+		error = xfs_metadir_load(tp, mp->m_rtdirip, path,
+				ops->metafile_type, &ip);
+		kfree(path);
+	}
+
+	if (error) {
+		if (xfs_metadata_is_sick(error))
+			xfs_rtginode_mark_sick(rtg, type);
+		return error;
+	}
+
+	if (XFS_IS_CORRUPT(mp, ip->i_df.if_format != XFS_DINODE_FMT_EXTENTS &&
+			       ip->i_df.if_format != XFS_DINODE_FMT_BTREE)) {
+		xfs_irele(ip);
+		xfs_rtginode_mark_sick(rtg, type);
+		return -EFSCORRUPTED;
+	}
+
+	if (XFS_IS_CORRUPT(mp, ip->i_projid != rtg_rgno(rtg))) {
+		xfs_irele(ip);
+		xfs_rtginode_mark_sick(rtg, type);
+		return -EFSCORRUPTED;
+	}
+
+	xfs_rtginode_lockdep_setup(ip, rtg_rgno(rtg), type);
+	rtg->rtg_inodes[type] = ip;
+	return 0;
+}
+
+/* Release an rtgroup metadata inode. */
+void
+xfs_rtginode_irele(
+	struct xfs_inode	**ipp)
+{
+	if (*ipp)
+		xfs_irele(*ipp);
+	*ipp = NULL;
+}
+
+/* Add a metadata inode for a realtime rmap btree. */
+int
+xfs_rtginode_create(
+	struct xfs_rtgroup		*rtg,
+	enum xfs_rtg_inodes		type,
+	bool				init)
+{
+	const struct xfs_rtginode_ops	*ops = &xfs_rtginode_ops[type];
+	struct xfs_mount		*mp = rtg_mount(rtg);
+	struct xfs_metadir_update	upd = {
+		.dp			= mp->m_rtdirip,
+		.metafile_type		= ops->metafile_type,
+	};
+	int				error;
+
+	if (!xfs_rtginode_enabled(rtg, type))
+		return 0;
+
+	if (!mp->m_rtdirip) {
+		xfs_fs_mark_sick(mp, XFS_SICK_FS_METADIR);
+		return -EFSCORRUPTED;
+	}
+
+	upd.path = xfs_rtginode_path(rtg_rgno(rtg), type);
+	if (!upd.path)
+		return -ENOMEM;
+
+	error = xfs_metadir_start_create(&upd);
+	if (error)
+		goto out_path;
+
+	error = xfs_metadir_create(&upd, S_IFREG);
+	if (error)
+		return error;
+
+	xfs_rtginode_lockdep_setup(upd.ip, rtg_rgno(rtg), type);
+
+	upd.ip->i_projid = rtg_rgno(rtg);
+	error = ops->create(rtg, upd.ip, upd.tp, init);
+	if (error)
+		goto out_cancel;
+
+	error = xfs_metadir_commit(&upd);
+	if (error)
+		goto out_path;
+
+	kfree(upd.path);
+	xfs_finish_inode_setup(upd.ip);
+	rtg->rtg_inodes[type] = upd.ip;
+	return 0;
+
+out_cancel:
+	xfs_metadir_cancel(&upd, error);
+	/* Have to finish setting up the inode to ensure it's deleted. */
+	if (upd.ip) {
+		xfs_finish_inode_setup(upd.ip);
+		xfs_irele(upd.ip);
+	}
+out_path:
+	kfree(upd.path);
+	return error;
+}
+
+/* Create the parent directory for all rtgroup inodes and load it. */
+int
+xfs_rtginode_mkdir_parent(
+	struct xfs_mount	*mp)
+{
+	if (!mp->m_metadirip) {
+		xfs_fs_mark_sick(mp, XFS_SICK_FS_METADIR);
+		return -EFSCORRUPTED;
+	}
+
+	return xfs_metadir_mkdir(mp->m_metadirip, "rtgroups", &mp->m_rtdirip);
+}
+
+/* Load the parent directory of all rtgroup inodes. */
+int
+xfs_rtginode_load_parent(
+	struct xfs_trans	*tp)
+{
+	struct xfs_mount	*mp = tp->t_mountp;
+
+	if (!mp->m_metadirip) {
+		xfs_fs_mark_sick(mp, XFS_SICK_FS_METADIR);
+		return -EFSCORRUPTED;
+	}
+
+	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,
+};
+
+/* Update a realtime superblock from the primary fs super */
+void
+xfs_update_rtsb(
+	struct xfs_buf		*rtsb_bp,
+	const struct xfs_buf	*sb_bp)
+{
+	const struct xfs_dsb	*dsb = sb_bp->b_addr;
+	struct xfs_rtsb		*rsb = rtsb_bp->b_addr;
+	const uuid_t		*meta_uuid;
+
+	rsb->rsb_magicnum = cpu_to_be32(XFS_RTSB_MAGIC);
+
+	rsb->rsb_pad = 0;
+	memcpy(&rsb->rsb_fname, &dsb->sb_fname, XFSLABEL_MAX);
+
+	memcpy(&rsb->rsb_uuid, &dsb->sb_uuid, sizeof(rsb->rsb_uuid));
+
+	/*
+	 * The metadata uuid is the fs uuid if the metauuid feature is not
+	 * enabled.
+	 */
+	if (dsb->sb_features_incompat &
+				cpu_to_be32(XFS_SB_FEAT_INCOMPAT_META_UUID))
+		meta_uuid = &dsb->sb_meta_uuid;
+	else
+		meta_uuid = &dsb->sb_uuid;
+	memcpy(&rsb->rsb_meta_uuid, meta_uuid, sizeof(rsb->rsb_meta_uuid));
+}
+
+/*
+ * Update the realtime superblock from a filesystem superblock and log it to
+ * the given transaction.
+ */
+struct xfs_buf *
+xfs_log_rtsb(
+	struct xfs_trans	*tp,
+	const struct xfs_buf	*sb_bp)
+{
+	struct xfs_buf		*rtsb_bp;
+
+	if (!xfs_has_rtsb(tp->t_mountp))
+		return NULL;
+
+	rtsb_bp = xfs_trans_getrtsb(tp);
+	if (!rtsb_bp) {
+		/*
+		 * It's possible for the rtgroups feature to be enabled but
+		 * there is no incore rt superblock buffer if the rt geometry
+		 * was specified at mkfs time but the rt section has not yet
+		 * been attached.  In this case, rblocks must be zero.
+		 */
+		ASSERT(tp->t_mountp->m_sb.sb_rblocks == 0);
+		return NULL;
+	}
+
+	xfs_update_rtsb(rtsb_bp, sb_bp);
+	xfs_trans_ordered_buf(tp, rtsb_bp);
+	return rtsb_bp;
+}