refcount.c | Explore in Territory

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2017-2023 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <[email protected]>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_trans.h"
#include "xfs_ag.h"
#include "xfs_btree.h"
#include "xfs_rmap.h"
#include "xfs_refcount.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/btree.h"
#include "scrub/trace.h"
#include "scrub/repair.h"

/*
 * Set us up to scrub reference count btrees.
 */
int
xchk_setup_ag_refcountbt(
	struct xfs_scrub	*sc)
{ … }

/* Reference count btree scrubber. */

/*
 * Confirming Reference Counts via Reverse Mappings
 *
 * We want to count the reverse mappings overlapping a refcount record
 * (bno, len, refcount), allowing for the possibility that some of the
 * overlap may come from smaller adjoining reverse mappings, while some
 * comes from single extents which overlap the range entirely.  The
 * outer loop is as follows:
 *
 * 1. For all reverse mappings overlapping the refcount extent,
 *    a. If a given rmap completely overlaps, mark it as seen.
 *    b. Otherwise, record the fragment (in agbno order) for later
 *       processing.
 *
 * Once we've seen all the rmaps, we know that for all blocks in the
 * refcount record we want to find $refcount owners and we've already
 * visited $seen extents that overlap all the blocks.  Therefore, we
 * need to find ($refcount - $seen) owners for every block in the
 * extent; call that quantity $target_nr.  Proceed as follows:
 *
 * 2. Pull the first $target_nr fragments from the list; all of them
 *    should start at or before the start of the extent.
 *    Call this subset of fragments the working set.
 * 3. Until there are no more unprocessed fragments,
 *    a. Find the shortest fragments in the set and remove them.
 *    b. Note the block number of the end of these fragments.
 *    c. Pull the same number of fragments from the list.  All of these
 *       fragments should start at the block number recorded in the
 *       previous step.
 *    d. Put those fragments in the set.
 * 4. Check that there are $target_nr fragments remaining in the list,
 *    and that they all end at or beyond the end of the refcount extent.
 *
 * If the refcount is correct, all the check conditions in the algorithm
 * should always hold true.  If not, the refcount is incorrect.
 */
struct xchk_refcnt_frag { … };

struct xchk_refcnt_check { … };

/*
 * Decide if the given rmap is large enough that we can redeem it
 * towards refcount verification now, or if it's a fragment, in
 * which case we'll hang onto it in the hopes that we'll later
 * discover that we've collected exactly the correct number of
 * fragments as the refcountbt says we should have.
 */
STATIC int
xchk_refcountbt_rmap_check(
	struct xfs_btree_cur		*cur,
	const struct xfs_rmap_irec	*rec,
	void				*priv)
{ … }

/*
 * Given a bunch of rmap fragments, iterate through them, keeping
 * a running tally of the refcount.  If this ever deviates from
 * what we expect (which is the refcountbt's refcount minus the
 * number of extents that totally covered the refcountbt extent),
 * we have a refcountbt error.
 */
STATIC void
xchk_refcountbt_process_rmap_fragments(
	struct xchk_refcnt_check	*refchk)
{ … }

/* Use the rmap entries covering this extent to verify the refcount. */
STATIC void
xchk_refcountbt_xref_rmap(
	struct xfs_scrub		*sc,
	const struct xfs_refcount_irec	*irec)
{ … }

/* Cross-reference with the other btrees. */
STATIC void
xchk_refcountbt_xref(
	struct xfs_scrub		*sc,
	const struct xfs_refcount_irec	*irec)
{ … }

struct xchk_refcbt_records { … };

STATIC int
xchk_refcountbt_rmap_check_gap(
	struct xfs_btree_cur		*cur,
	const struct xfs_rmap_irec	*rec,
	void				*priv)
{ … }

/*
 * Make sure that a gap in the reference count records does not correspond to
 * overlapping records (i.e. shared extents) in the reverse mappings.
 */
static inline void
xchk_refcountbt_xref_gaps(
	struct xfs_scrub	*sc,
	struct xchk_refcbt_records *rrc,
	xfs_agblock_t		bno)
{ … }

static inline bool
xchk_refcount_mergeable(
	struct xchk_refcbt_records	*rrc,
	const struct xfs_refcount_irec	*r2)
{ … }

/* Flag failures for records that could be merged. */
STATIC void
xchk_refcountbt_check_mergeable(
	struct xchk_btree		*bs,
	struct xchk_refcbt_records	*rrc,
	const struct xfs_refcount_irec	*irec)
{ … }

/* Scrub a refcountbt record. */
STATIC int
xchk_refcountbt_rec(
	struct xchk_btree	*bs,
	const union xfs_btree_rec *rec)
{ … }

/* Make sure we have as many refc blocks as the rmap says. */
STATIC void
xchk_refcount_xref_rmap(
	struct xfs_scrub	*sc,
	xfs_filblks_t		cow_blocks)
{ … }

/* Scrub the refcount btree for some AG. */
int
xchk_refcountbt(
	struct xfs_scrub	*sc)
{ … }

/* xref check that a cow staging extent is marked in the refcountbt. */
void
xchk_xref_is_cow_staging(
	struct xfs_scrub		*sc,
	xfs_agblock_t			agbno,
	xfs_extlen_t			len)
{ … }

/*
 * xref check that the extent is not shared.  Only file data blocks
 * can have multiple owners.
 */
void
xchk_xref_is_not_shared(
	struct xfs_scrub	*sc,
	xfs_agblock_t		agbno,
	xfs_extlen_t		len)
{ … }

/* xref check that the extent is not being used for CoW staging. */
void
xchk_xref_is_not_cow_staging(
	struct xfs_scrub	*sc,
	xfs_agblock_t		agbno,
	xfs_extlen_t		len)
{ … }
linux/fs/xfs/scrub/refcount.c
