diff mbox series

[5/7] xfs: implement block reservation accounting for btrees we're staging

Message ID 170086926207.2768790.3907390620269991796.stgit@frogsfrogsfrogs (mailing list archive)
State New
Headers show
Series xfs: reserve disk space for online repairs | expand

Commit Message

Darrick J. Wong Nov. 24, 2023, 11:48 p.m. UTC
From: Darrick J. Wong <djwong@kernel.org>

Create a new xrep_newbt structure to encapsulate a fake root for
creating a staged btree cursor as well as to track all the blocks that
we need to reserve in order to build that btree.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/Makefile                   |    1 
 fs/xfs/libxfs/xfs_btree_staging.h |    7 -
 fs/xfs/scrub/agheader_repair.c    |    1 
 fs/xfs/scrub/common.c             |    1 
 fs/xfs/scrub/newbt.c              |  492 +++++++++++++++++++++++++++++++++++++
 fs/xfs/scrub/newbt.h              |   62 +++++
 fs/xfs/scrub/scrub.c              |    2 
 fs/xfs/scrub/trace.h              |   37 +++
 8 files changed, 598 insertions(+), 5 deletions(-)
 create mode 100644 fs/xfs/scrub/newbt.c
 create mode 100644 fs/xfs/scrub/newbt.h

Comments

Christoph Hellwig Nov. 26, 2023, 1:14 p.m. UTC | #1
The data structure and support code looks fine to me, but I do have
some nitpicky comments and questions:

> -	/* Fork format. */
> -	unsigned int		if_format;
> -
> -	/* Number of records. */
> -	unsigned int		if_extents;
> +	/* Which fork is this btree being built for? */
> +	int			if_whichfork;

The two removed fields seems to be unused even before this patch.
Should they have been in a separate removal patch?

> diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
> index 876a2f41b0637..36c511f96b004 100644
> --- a/fs/xfs/scrub/agheader_repair.c
> +++ b/fs/xfs/scrub/agheader_repair.c
> @@ -10,6 +10,7 @@
>  #include "xfs_trans_resv.h"
>  #include "xfs_mount.h"
>  #include "xfs_btree.h"
> +#include "xfs_btree_staging.h"
>  #include "xfs_log_format.h"
>  #include "xfs_trans.h"
>  #include "xfs_sb.h"

I also don't think all the #include churn belongs into this patch,
as the only existing header touched by it is xfs_btree_staging.h,
which means that anything that didn't need it before still won't
need it with the changes.

> +/*
> + * Estimate proper slack values for a btree that's being reloaded.
> + *
> + * Under most circumstances, we'll take whatever default loading value the
> + * btree bulk loading code calculates for us.  However, there are some
> + * exceptions to this rule:
> + *
> + * (1) If someone turned one of the debug knobs.
> + * (2) If this is a per-AG btree and the AG has less than ~9% space free.
> + * (3) If this is an inode btree and the FS has less than ~9% space free.

Where does this ~9% number come from?  Obviously it is a low-space
condition of some sort, but I wonder what are the criteria.  It would
be nice to document that here, even if the answer is
answer is "out of thin air".

> + * Note that we actually use 3/32 for the comparison to avoid division.
> + */
> +static void

> +	/* No further changes if there's more than 3/32ths space left. */
> +	if (free >= ((sz * 3) >> 5))
> +		return;

Is this code really in the critical path that a division (or relying
on the compiler to do the right thing) is out of question?  Because
these shits by magic numbers are really annyoing to read (unlike
say normal SECTOR_SHIFT or PAGE_SHIFT ones that are fairly easy to
read).
Darrick J. Wong Nov. 27, 2023, 10:34 p.m. UTC | #2
On Sun, Nov 26, 2023 at 05:14:53AM -0800, Christoph Hellwig wrote:
> The data structure and support code looks fine to me, but I do have
> some nitpicky comments and questions:
> 
> > -	/* Fork format. */
> > -	unsigned int		if_format;
> > -
> > -	/* Number of records. */
> > -	unsigned int		if_extents;
> > +	/* Which fork is this btree being built for? */
> > +	int			if_whichfork;
> 
> The two removed fields seems to be unused even before this patch.
> Should they have been in a separate removal patch?

They should have been in the patch that moved if_{format,extents} into
xfs_inode_fork:

daf83964a3681 ("xfs: move the per-fork nextents fields into struct xfs_ifork")
f7e67b20ecbbc ("xfs: move the fork format fields into struct xfs_ifork")

but I think it just got lost in the review of all that back in May 2020.
Since then the design has changed enough that I don't even think the
if_whichfork field is in use anywhere:

$ git grep if_whichfork
fs/xfs/libxfs/xfs_bmap_btree.c:664:     cur = xfs_bmbt_init_common(mp, NULL, ip, ifake->if_whichfork);
fs/xfs/libxfs/xfs_btree_staging.h:42:   int                     if_whichfork;
fs/xfs/scrub/newbt.c:117:       xnr->ifake.if_whichfork = whichfork;
fs/xfs/scrub/newbt.c:156:       xnr->ifake.if_whichfork = XFS_DATA_FORK;

$ cd ../xfsprogs/
$ git grep if_whichfork
db/bmap_inflate.c:367:  ifake.if_whichfork = XFS_DATA_FORK;
db/bmap_inflate.c:421:  ifake.if_whichfork = XFS_DATA_FORK;
libxfs/xfs_bmap_btree.c:662:    cur = xfs_bmbt_init_common(mp, NULL, ip, ifake->if_whichfork);
libxfs/xfs_btree_staging.h:42:  int                     if_whichfork;
repair/bulkload.c:38:   bkl->ifake.if_whichfork = whichfork;

So that can all go away.

> > diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
> > index 876a2f41b0637..36c511f96b004 100644
> > --- a/fs/xfs/scrub/agheader_repair.c
> > +++ b/fs/xfs/scrub/agheader_repair.c
> > @@ -10,6 +10,7 @@
> >  #include "xfs_trans_resv.h"
> >  #include "xfs_mount.h"
> >  #include "xfs_btree.h"
> > +#include "xfs_btree_staging.h"
> >  #include "xfs_log_format.h"
> >  #include "xfs_trans.h"
> >  #include "xfs_sb.h"
> 
> I also don't think all the #include churn belongs into this patch,
> as the only existing header touched by it is xfs_btree_staging.h,
> which means that anything that didn't need it before still won't
> need it with the changes.

Hmm yeah.  Not sure when this detritus started accumulating here. :(

> > +/*
> > + * Estimate proper slack values for a btree that's being reloaded.
> > + *
> > + * Under most circumstances, we'll take whatever default loading value the
> > + * btree bulk loading code calculates for us.  However, there are some
> > + * exceptions to this rule:
> > + *
> > + * (1) If someone turned one of the debug knobs.
> > + * (2) If this is a per-AG btree and the AG has less than ~9% space free.
> > + * (3) If this is an inode btree and the FS has less than ~9% space free.
> 
> Where does this ~9% number come from?  Obviously it is a low-space
> condition of some sort, but I wonder what are the criteria.  It would
> be nice to document that here, even if the answer is
> answer is "out of thin air".

It comes from xfs_repair:
https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/tree/repair/bulkload.c?h=for-next#n114

Before xfs_btree_staging.[ch] came along, it was open coded in
repair/phase5.c in a most unglorious fashion:
https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/tree/repair/phase5.c?h=v4.19.0#n1349

At that point the slack factors were arbitrary quantities per btree.
The rmapbt automatically left 10 slots free; everything else left zero.

That had a noticeable effect on performance straight after mounting
because touching /any/ btree would result in splits.  IIRC Dave and I
decided that repair should generate btree blocks that were 75% full
unless space was tight.  We defined tight as ~10% free to avoid repair
failures and settled on 3/32 to avoid div64.

IOWs, we mostly pulled it out of thin air. ;)

OFC the other weird thing is that originally I thought that online
repair would land sooner than would the retroport of xfs_repair to the
new btree bulk loading code.

> > + * Note that we actually use 3/32 for the comparison to avoid division.
> > + */
> > +static void
> 
> > +	/* No further changes if there's more than 3/32ths space left. */
> > +	if (free >= ((sz * 3) >> 5))
> > +		return;
> 
> Is this code really in the critical path that a division (or relying
> on the compiler to do the right thing) is out of question?  Because
> these shits by magic numbers are really annyoing to read (unlike
> say normal SECTOR_SHIFT or PAGE_SHIFT ones that are fairly easy to
> read).

Nah, it's not performance critical.  Collecting records and formatting
blocks is a much bigger strain on the system than a few divisions.  I'll
change it to div_u64(sz, 10).

Hmm now that I look at it, I've also noticed that even the lowspace
btree rebuild in userspace will leave two open slots per block.

--D
Christoph Hellwig Nov. 28, 2023, 5:41 a.m. UTC | #3
On Mon, Nov 27, 2023 at 02:34:51PM -0800, Darrick J. Wong wrote:
> That had a noticeable effect on performance straight after mounting
> because touching /any/ btree would result in splits.  IIRC Dave and I
> decided that repair should generate btree blocks that were 75% full
> unless space was tight.  We defined tight as ~10% free to avoid repair
> failures and settled on 3/32 to avoid div64.
> 
> IOWs, we mostly pulled it out of thin air. ;)

Maybe throw a little comment about this in.
Darrick J. Wong Nov. 28, 2023, 5:02 p.m. UTC | #4
On Mon, Nov 27, 2023 at 09:41:28PM -0800, Christoph Hellwig wrote:
> On Mon, Nov 27, 2023 at 02:34:51PM -0800, Darrick J. Wong wrote:
> > That had a noticeable effect on performance straight after mounting
> > because touching /any/ btree would result in splits.  IIRC Dave and I
> > decided that repair should generate btree blocks that were 75% full
> > unless space was tight.  We defined tight as ~10% free to avoid repair
> > failures and settled on 3/32 to avoid div64.
> > 
> > IOWs, we mostly pulled it out of thin air. ;)
> 
> Maybe throw a little comment about this in.

Yeah, I'll paste the sordid history into the commit message when I
change the code to use div_u64.

--D
diff mbox series

Patch

diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index 7762c01a85cfb..1537d66e5ab01 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -181,6 +181,7 @@  xfs-$(CONFIG_XFS_QUOTA)		+= scrub/quota.o
 ifeq ($(CONFIG_XFS_ONLINE_REPAIR),y)
 xfs-y				+= $(addprefix scrub/, \
 				   agheader_repair.o \
+				   newbt.o \
 				   reap.o \
 				   repair.o \
 				   )
diff --git a/fs/xfs/libxfs/xfs_btree_staging.h b/fs/xfs/libxfs/xfs_btree_staging.h
index f0d2976050aea..d6dea3f0088c6 100644
--- a/fs/xfs/libxfs/xfs_btree_staging.h
+++ b/fs/xfs/libxfs/xfs_btree_staging.h
@@ -38,11 +38,8 @@  struct xbtree_ifakeroot {
 	/* Number of bytes available for this fork in the inode. */
 	unsigned int		if_fork_size;
 
-	/* Fork format. */
-	unsigned int		if_format;
-
-	/* Number of records. */
-	unsigned int		if_extents;
+	/* Which fork is this btree being built for? */
+	int			if_whichfork;
 };
 
 /* Cursor interactions with fake roots for inode-rooted btrees. */
diff --git a/fs/xfs/scrub/agheader_repair.c b/fs/xfs/scrub/agheader_repair.c
index 876a2f41b0637..36c511f96b004 100644
--- a/fs/xfs/scrub/agheader_repair.c
+++ b/fs/xfs/scrub/agheader_repair.c
@@ -10,6 +10,7 @@ 
 #include "xfs_trans_resv.h"
 #include "xfs_mount.h"
 #include "xfs_btree.h"
+#include "xfs_btree_staging.h"
 #include "xfs_log_format.h"
 #include "xfs_trans.h"
 #include "xfs_sb.h"
diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
index 23944fcc1a6ca..4bba3c49f8c59 100644
--- a/fs/xfs/scrub/common.c
+++ b/fs/xfs/scrub/common.c
@@ -10,6 +10,7 @@ 
 #include "xfs_trans_resv.h"
 #include "xfs_mount.h"
 #include "xfs_btree.h"
+#include "xfs_btree_staging.h"
 #include "xfs_log_format.h"
 #include "xfs_trans.h"
 #include "xfs_inode.h"
diff --git a/fs/xfs/scrub/newbt.c b/fs/xfs/scrub/newbt.c
new file mode 100644
index 0000000000000..4e8d6637426e4
--- /dev/null
+++ b/fs/xfs/scrub/newbt.c
@@ -0,0 +1,492 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2022-2023 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_mount.h"
+#include "xfs_btree.h"
+#include "xfs_btree_staging.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_inode.h"
+#include "xfs_alloc.h"
+#include "xfs_rmap.h"
+#include "xfs_ag.h"
+#include "xfs_defer.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+#include "scrub/newbt.h"
+
+/*
+ * Estimate proper slack values for a btree that's being reloaded.
+ *
+ * Under most circumstances, we'll take whatever default loading value the
+ * btree bulk loading code calculates for us.  However, there are some
+ * exceptions to this rule:
+ *
+ * (1) If someone turned one of the debug knobs.
+ * (2) If this is a per-AG btree and the AG has less than ~9% space free.
+ * (3) If this is an inode btree and the FS has less than ~9% space free.
+ *
+ * Note that we actually use 3/32 for the comparison to avoid division.
+ */
+static void
+xrep_newbt_estimate_slack(
+	struct xrep_newbt	*xnr)
+{
+	struct xfs_scrub	*sc = xnr->sc;
+	struct xfs_btree_bload	*bload = &xnr->bload;
+	uint64_t		free;
+	uint64_t		sz;
+
+	/* Let the btree code compute the default slack values. */
+	bload->leaf_slack = -1;
+	bload->node_slack = -1;
+
+	if (sc->ops->type == ST_PERAG) {
+		free = sc->sa.pag->pagf_freeblks;
+		sz = xfs_ag_block_count(sc->mp, sc->sa.pag->pag_agno);
+	} else {
+		free = percpu_counter_sum(&sc->mp->m_fdblocks);
+		sz = sc->mp->m_sb.sb_dblocks;
+	}
+
+	/* No further changes if there's more than 3/32ths space left. */
+	if (free >= ((sz * 3) >> 5))
+		return;
+
+	/* We're low on space; load the btrees as tightly as possible. */
+	if (bload->leaf_slack < 0)
+		bload->leaf_slack = 0;
+	if (bload->node_slack < 0)
+		bload->node_slack = 0;
+}
+
+/* Initialize accounting resources for staging a new AG btree. */
+void
+xrep_newbt_init_ag(
+	struct xrep_newbt		*xnr,
+	struct xfs_scrub		*sc,
+	const struct xfs_owner_info	*oinfo,
+	xfs_fsblock_t			alloc_hint,
+	enum xfs_ag_resv_type		resv)
+{
+	memset(xnr, 0, sizeof(struct xrep_newbt));
+	xnr->sc = sc;
+	xnr->oinfo = *oinfo; /* structure copy */
+	xnr->alloc_hint = alloc_hint;
+	xnr->resv = resv;
+	INIT_LIST_HEAD(&xnr->resv_list);
+	xrep_newbt_estimate_slack(xnr);
+}
+
+/* Initialize accounting resources for staging a new inode fork btree. */
+int
+xrep_newbt_init_inode(
+	struct xrep_newbt		*xnr,
+	struct xfs_scrub		*sc,
+	int				whichfork,
+	const struct xfs_owner_info	*oinfo)
+{
+	struct xfs_ifork		*ifp;
+
+	ifp = kmem_cache_zalloc(xfs_ifork_cache, XCHK_GFP_FLAGS);
+	if (!ifp)
+		return -ENOMEM;
+
+	xrep_newbt_init_ag(xnr, sc, oinfo,
+			XFS_INO_TO_FSB(sc->mp, sc->ip->i_ino),
+			XFS_AG_RESV_NONE);
+	xnr->ifake.if_fork = ifp;
+	xnr->ifake.if_fork_size = xfs_inode_fork_size(sc->ip, whichfork);
+	xnr->ifake.if_whichfork = whichfork;
+	return 0;
+}
+
+/*
+ * Initialize accounting resources for staging a new btree.  Callers are
+ * expected to add their own reservations (and clean them up) manually.
+ */
+void
+xrep_newbt_init_bare(
+	struct xrep_newbt		*xnr,
+	struct xfs_scrub		*sc)
+{
+	xrep_newbt_init_ag(xnr, sc, &XFS_RMAP_OINFO_ANY_OWNER, NULLFSBLOCK,
+			XFS_AG_RESV_NONE);
+}
+
+/*
+ * Designate specific blocks to be used to build our new btree.  @pag must be
+ * a passive reference.
+ */
+STATIC int
+xrep_newbt_add_blocks(
+	struct xrep_newbt		*xnr,
+	struct xfs_perag		*pag,
+	const struct xfs_alloc_arg	*args)
+{
+	struct xfs_mount		*mp = xnr->sc->mp;
+	struct xrep_newbt_resv		*resv;
+
+	resv = kmalloc(sizeof(struct xrep_newbt_resv), XCHK_GFP_FLAGS);
+	if (!resv)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&resv->list);
+	resv->agbno = XFS_FSB_TO_AGBNO(mp, args->fsbno);
+	resv->len = args->len;
+	resv->used = 0;
+	resv->pag = xfs_perag_hold(pag);
+
+	list_add_tail(&resv->list, &xnr->resv_list);
+	return 0;
+}
+
+/* Don't let our allocation hint take us beyond this AG */
+static inline void
+xrep_newbt_validate_ag_alloc_hint(
+	struct xrep_newbt	*xnr)
+{
+	struct xfs_scrub	*sc = xnr->sc;
+	xfs_agnumber_t		agno = XFS_FSB_TO_AGNO(sc->mp, xnr->alloc_hint);
+
+	if (agno == sc->sa.pag->pag_agno &&
+	    xfs_verify_fsbno(sc->mp, xnr->alloc_hint))
+		return;
+
+	xnr->alloc_hint = XFS_AGB_TO_FSB(sc->mp, sc->sa.pag->pag_agno,
+					 XFS_AGFL_BLOCK(sc->mp) + 1);
+}
+
+/* Allocate disk space for a new per-AG btree. */
+STATIC int
+xrep_newbt_alloc_ag_blocks(
+	struct xrep_newbt	*xnr,
+	uint64_t		nr_blocks)
+{
+	struct xfs_scrub	*sc = xnr->sc;
+	struct xfs_mount	*mp = sc->mp;
+	int			error = 0;
+
+	ASSERT(sc->sa.pag != NULL);
+
+	while (nr_blocks > 0) {
+		struct xfs_alloc_arg	args = {
+			.tp		= sc->tp,
+			.mp		= mp,
+			.oinfo		= xnr->oinfo,
+			.minlen		= 1,
+			.maxlen		= nr_blocks,
+			.prod		= 1,
+			.resv		= xnr->resv,
+		};
+		xfs_agnumber_t		agno;
+
+		xrep_newbt_validate_ag_alloc_hint(xnr);
+
+		error = xfs_alloc_vextent_near_bno(&args, xnr->alloc_hint);
+		if (error)
+			return error;
+		if (args.fsbno == NULLFSBLOCK)
+			return -ENOSPC;
+
+		agno = XFS_FSB_TO_AGNO(mp, args.fsbno);
+
+		trace_xrep_newbt_alloc_ag_blocks(mp, agno,
+				XFS_FSB_TO_AGBNO(mp, args.fsbno), args.len,
+				xnr->oinfo.oi_owner);
+
+		if (agno != sc->sa.pag->pag_agno) {
+			ASSERT(agno == sc->sa.pag->pag_agno);
+			return -EFSCORRUPTED;
+		}
+
+		error = xrep_newbt_add_blocks(xnr, sc->sa.pag, &args);
+		if (error)
+			return error;
+
+		nr_blocks -= args.len;
+		xnr->alloc_hint = args.fsbno + args.len;
+
+		error = xrep_defer_finish(sc);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+/* Don't let our allocation hint take us beyond EOFS */
+static inline void
+xrep_newbt_validate_file_alloc_hint(
+	struct xrep_newbt	*xnr)
+{
+	struct xfs_scrub	*sc = xnr->sc;
+
+	if (xfs_verify_fsbno(sc->mp, xnr->alloc_hint))
+		return;
+
+	xnr->alloc_hint = XFS_AGB_TO_FSB(sc->mp, 0, XFS_AGFL_BLOCK(sc->mp) + 1);
+}
+
+/* Allocate disk space for our new file-based btree. */
+STATIC int
+xrep_newbt_alloc_file_blocks(
+	struct xrep_newbt	*xnr,
+	uint64_t		nr_blocks)
+{
+	struct xfs_scrub	*sc = xnr->sc;
+	struct xfs_mount	*mp = sc->mp;
+	int			error = 0;
+
+	while (nr_blocks > 0) {
+		struct xfs_alloc_arg	args = {
+			.tp		= sc->tp,
+			.mp		= mp,
+			.oinfo		= xnr->oinfo,
+			.minlen		= 1,
+			.maxlen		= nr_blocks,
+			.prod		= 1,
+			.resv		= xnr->resv,
+		};
+		struct xfs_perag	*pag;
+		xfs_agnumber_t		agno;
+
+		xrep_newbt_validate_file_alloc_hint(xnr);
+
+		error = xfs_alloc_vextent_start_ag(&args, xnr->alloc_hint);
+		if (error)
+			return error;
+		if (args.fsbno == NULLFSBLOCK)
+			return -ENOSPC;
+
+		agno = XFS_FSB_TO_AGNO(mp, args.fsbno);
+
+		trace_xrep_newbt_alloc_file_blocks(mp, agno,
+				XFS_FSB_TO_AGBNO(mp, args.fsbno), args.len,
+				xnr->oinfo.oi_owner);
+
+		pag = xfs_perag_get(mp, agno);
+		if (!pag) {
+			ASSERT(0);
+			return -EFSCORRUPTED;
+		}
+
+		error = xrep_newbt_add_blocks(xnr, pag, &args);
+		xfs_perag_put(pag);
+		if (error)
+			return error;
+
+		nr_blocks -= args.len;
+		xnr->alloc_hint = args.fsbno + args.len;
+
+		error = xrep_defer_finish(sc);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+/* Allocate disk space for our new btree. */
+int
+xrep_newbt_alloc_blocks(
+	struct xrep_newbt	*xnr,
+	uint64_t		nr_blocks)
+{
+	if (xnr->sc->ip)
+		return xrep_newbt_alloc_file_blocks(xnr, nr_blocks);
+	return xrep_newbt_alloc_ag_blocks(xnr, nr_blocks);
+}
+
+/*
+ * Free the unused part of a space extent that was reserved for a new ondisk
+ * structure.  Returns the number of EFIs logged or a negative errno.
+ */
+STATIC int
+xrep_newbt_free_extent(
+	struct xrep_newbt	*xnr,
+	struct xrep_newbt_resv	*resv,
+	bool			btree_committed)
+{
+	struct xfs_scrub	*sc = xnr->sc;
+	xfs_agblock_t		free_agbno = resv->agbno;
+	xfs_extlen_t		free_aglen = resv->len;
+	xfs_fsblock_t		fsbno;
+	int			error;
+
+	if (!btree_committed || resv->used == 0) {
+		/*
+		 * If we're not committing a new btree or we didn't use the
+		 * space reservation, free the entire space extent.
+		 */
+		goto free;
+	}
+
+	/*
+	 * We used space and committed the btree.  Remove the written blocks
+	 * from the reservation and possibly log a new EFI to free any unused
+	 * reservation space.
+	 */
+	free_agbno += resv->used;
+	free_aglen -= resv->used;
+
+	if (free_aglen == 0)
+		return 0;
+
+	trace_xrep_newbt_free_blocks(sc->mp, resv->pag->pag_agno, free_agbno,
+			free_aglen, xnr->oinfo.oi_owner);
+
+	ASSERT(xnr->resv != XFS_AG_RESV_AGFL);
+
+free:
+	/*
+	 * Use EFIs to free the reservations.  This reduces the chance
+	 * that we leak blocks if the system goes down.
+	 */
+	fsbno = XFS_AGB_TO_FSB(sc->mp, resv->pag->pag_agno, free_agbno);
+	error = xfs_free_extent_later(sc->tp, fsbno, free_aglen, &xnr->oinfo,
+			xnr->resv, true);
+	if (error)
+		return error;
+
+	return 1;
+}
+
+/* Free all the accounting info and disk space we reserved for a new btree. */
+STATIC int
+xrep_newbt_free(
+	struct xrep_newbt	*xnr,
+	bool			btree_committed)
+{
+	struct xfs_scrub	*sc = xnr->sc;
+	struct xrep_newbt_resv	*resv, *n;
+	unsigned int		freed = 0;
+	int			error = 0;
+
+	/*
+	 * If the filesystem already went down, we can't free the blocks.  Skip
+	 * ahead to freeing the incore metadata because we can't fix anything.
+	 */
+	if (xfs_is_shutdown(sc->mp))
+		goto junkit;
+
+	list_for_each_entry_safe(resv, n, &xnr->resv_list, list) {
+		int		ret;
+
+		ret = xrep_newbt_free_extent(xnr, resv, btree_committed);
+		list_del(&resv->list);
+		xfs_perag_put(resv->pag);
+		kfree(resv);
+		if (ret < 0) {
+			error = ret;
+			goto junkit;
+		}
+
+		freed += ret;
+		if (freed >= XREP_MAX_ITRUNCATE_EFIS) {
+			error = xrep_defer_finish(sc);
+			if (error)
+				goto junkit;
+			freed = 0;
+		}
+	}
+
+	if (freed)
+		error = xrep_defer_finish(sc);
+
+junkit:
+	/*
+	 * If we still have reservations attached to @newbt, cleanup must have
+	 * failed and the filesystem is about to go down.  Clean up the incore
+	 * reservations.
+	 */
+	list_for_each_entry_safe(resv, n, &xnr->resv_list, list) {
+		list_del(&resv->list);
+		xfs_perag_put(resv->pag);
+		kfree(resv);
+	}
+
+	if (sc->ip) {
+		kmem_cache_free(xfs_ifork_cache, xnr->ifake.if_fork);
+		xnr->ifake.if_fork = NULL;
+	}
+
+	return error;
+}
+
+/*
+ * Free all the accounting info and unused disk space allocations after
+ * committing a new btree.
+ */
+int
+xrep_newbt_commit(
+	struct xrep_newbt	*xnr)
+{
+	return xrep_newbt_free(xnr, true);
+}
+
+/*
+ * Free all the accounting info and all of the disk space we reserved for a new
+ * btree that we're not going to commit.  We want to try to roll things back
+ * cleanly for things like ENOSPC midway through allocation.
+ */
+void
+xrep_newbt_cancel(
+	struct xrep_newbt	*xnr)
+{
+	xrep_newbt_free(xnr, false);
+}
+
+/* Feed one of the reserved btree blocks to the bulk loader. */
+int
+xrep_newbt_claim_block(
+	struct xfs_btree_cur	*cur,
+	struct xrep_newbt	*xnr,
+	union xfs_btree_ptr	*ptr)
+{
+	struct xrep_newbt_resv	*resv;
+	struct xfs_mount	*mp = cur->bc_mp;
+	xfs_agblock_t		agbno;
+
+	/*
+	 * The first item in the list should always have a free block unless
+	 * we're completely out.
+	 */
+	resv = list_first_entry(&xnr->resv_list, struct xrep_newbt_resv, list);
+	if (resv->used == resv->len)
+		return -ENOSPC;
+
+	/*
+	 * Peel off a block from the start of the reservation.  We allocate
+	 * blocks in order to place blocks on disk in increasing record or key
+	 * order.  The block reservations tend to end up on the list in
+	 * decreasing order, which hopefully results in leaf blocks ending up
+	 * together.
+	 */
+	agbno = resv->agbno + resv->used;
+	resv->used++;
+
+	/* If we used all the blocks in this reservation, move it to the end. */
+	if (resv->used == resv->len)
+		list_move_tail(&resv->list, &xnr->resv_list);
+
+	trace_xrep_newbt_claim_block(mp, resv->pag->pag_agno, agbno, 1,
+			xnr->oinfo.oi_owner);
+
+	if (cur->bc_flags & XFS_BTREE_LONG_PTRS)
+		ptr->l = cpu_to_be64(XFS_AGB_TO_FSB(mp, resv->pag->pag_agno,
+								agbno));
+	else
+		ptr->s = cpu_to_be32(agbno);
+	return 0;
+}
diff --git a/fs/xfs/scrub/newbt.h b/fs/xfs/scrub/newbt.h
new file mode 100644
index 0000000000000..ca53271f3a4c6
--- /dev/null
+++ b/fs/xfs/scrub/newbt.h
@@ -0,0 +1,62 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2022-2023 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#ifndef __XFS_SCRUB_NEWBT_H__
+#define __XFS_SCRUB_NEWBT_H__
+
+struct xrep_newbt_resv {
+	/* Link to list of extents that we've reserved. */
+	struct list_head	list;
+
+	struct xfs_perag	*pag;
+
+	/* AG block of the extent we reserved. */
+	xfs_agblock_t		agbno;
+
+	/* Length of the reservation. */
+	xfs_extlen_t		len;
+
+	/* How much of this reservation has been used. */
+	xfs_extlen_t		used;
+};
+
+struct xrep_newbt {
+	struct xfs_scrub	*sc;
+
+	/* List of extents that we've reserved. */
+	struct list_head	resv_list;
+
+	/* Fake root for new btree. */
+	union {
+		struct xbtree_afakeroot	afake;
+		struct xbtree_ifakeroot	ifake;
+	};
+
+	/* rmap owner of these blocks */
+	struct xfs_owner_info	oinfo;
+
+	/* btree geometry for the bulk loader */
+	struct xfs_btree_bload	bload;
+
+	/* Allocation hint */
+	xfs_fsblock_t		alloc_hint;
+
+	/* per-ag reservation type */
+	enum xfs_ag_resv_type	resv;
+};
+
+void xrep_newbt_init_bare(struct xrep_newbt *xnr, struct xfs_scrub *sc);
+void xrep_newbt_init_ag(struct xrep_newbt *xnr, struct xfs_scrub *sc,
+		const struct xfs_owner_info *oinfo, xfs_fsblock_t alloc_hint,
+		enum xfs_ag_resv_type resv);
+int xrep_newbt_init_inode(struct xrep_newbt *xnr, struct xfs_scrub *sc,
+		int whichfork, const struct xfs_owner_info *oinfo);
+int xrep_newbt_alloc_blocks(struct xrep_newbt *xnr, uint64_t nr_blocks);
+void xrep_newbt_cancel(struct xrep_newbt *xnr);
+int xrep_newbt_commit(struct xrep_newbt *xnr);
+int xrep_newbt_claim_block(struct xfs_btree_cur *cur, struct xrep_newbt *xnr,
+		union xfs_btree_ptr *ptr);
+
+#endif /* __XFS_SCRUB_NEWBT_H__ */
diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index 4849efcaa33ae..474f4c4a9cd3b 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -17,6 +17,8 @@ 
 #include "xfs_errortag.h"
 #include "xfs_error.h"
 #include "xfs_scrub.h"
+#include "xfs_btree.h"
+#include "xfs_btree_staging.h"
 #include "scrub/scrub.h"
 #include "scrub/common.h"
 #include "scrub/trace.h"
diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 4a8bc6f3c8f2e..aa76830753196 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -1332,6 +1332,43 @@  TRACE_EVENT(xrep_ialloc_insert,
 		  __entry->freemask)
 )
 
+DECLARE_EVENT_CLASS(xrep_newbt_extent_class,
+	TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno,
+		 xfs_agblock_t agbno, xfs_extlen_t len,
+		 int64_t owner),
+	TP_ARGS(mp, agno, agbno, len, owner),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(xfs_agnumber_t, agno)
+		__field(xfs_agblock_t, agbno)
+		__field(xfs_extlen_t, len)
+		__field(int64_t, owner)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->agno = agno;
+		__entry->agbno = agbno;
+		__entry->len = len;
+		__entry->owner = owner;
+	),
+	TP_printk("dev %d:%d agno 0x%x agbno 0x%x fsbcount 0x%x owner 0x%llx",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->agno,
+		  __entry->agbno,
+		  __entry->len,
+		  __entry->owner)
+);
+#define DEFINE_NEWBT_EXTENT_EVENT(name) \
+DEFINE_EVENT(xrep_newbt_extent_class, name, \
+	TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno, \
+		 xfs_agblock_t agbno, xfs_extlen_t len, \
+		 int64_t owner), \
+	TP_ARGS(mp, agno, agbno, len, owner))
+DEFINE_NEWBT_EXTENT_EVENT(xrep_newbt_alloc_ag_blocks);
+DEFINE_NEWBT_EXTENT_EVENT(xrep_newbt_alloc_file_blocks);
+DEFINE_NEWBT_EXTENT_EVENT(xrep_newbt_free_blocks);
+DEFINE_NEWBT_EXTENT_EVENT(xrep_newbt_claim_block);
+
 #endif /* IS_ENABLED(CONFIG_XFS_ONLINE_REPAIR) */
 
 #endif /* _TRACE_XFS_SCRUB_TRACE_H */