linux/fs/xfs/scrub/rtrefcount_repair.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) 2021-2024 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <djwong@kernel.org>
 */
#include "xfs_platform.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_btree.h"
#include "xfs_btree_staging.h"
#include "xfs_bit.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_alloc.h"
#include "xfs_ialloc.h"
#include "xfs_rmap.h"
#include "xfs_rmap_btree.h"
#include "xfs_rtrmap_btree.h"
#include "xfs_refcount.h"
#include "xfs_rtrefcount_btree.h"
#include "xfs_error.h"
#include "xfs_health.h"
#include "xfs_inode.h"
#include "xfs_quota.h"
#include "xfs_rtalloc.h"
#include "xfs_ag.h"
#include "xfs_rtgroup.h"
#include "xfs_rtbitmap.h"
#include "scrub/xfs_scrub.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/btree.h"
#include "scrub/trace.h"
#include "scrub/repair.h"
#include "scrub/bitmap.h"
#include "scrub/fsb_bitmap.h"
#include "scrub/xfile.h"
#include "scrub/xfarray.h"
#include "scrub/newbt.h"
#include "scrub/reap.h"
#include "scrub/rcbag.h"

/*
 * Rebuilding the Reference Count Btree
 * ====================================
 *
 * This algorithm is "borrowed" from xfs_repair.  Imagine the rmap
 * entries as rectangles representing extents of physical blocks, and
 * that the rectangles can be laid down to allow them to overlap each
 * other; then we know that we must emit a refcnt btree entry wherever
 * the amount of overlap changes, i.e. the emission stimulus is
 * level-triggered:
 *
 *                 -    ---
 *       --      ----- ----   ---        ------
 * --   ----     ----------- ----     ---------
 * -------------------------------- -----------
 * ^ ^  ^^ ^^    ^ ^^ ^^^  ^^^^  ^ ^^ ^  ^     ^
 * 2 1  23 21    3 43 234  2123  1 01 2  3     0
 *
 * For our purposes, a rmap is a tuple (startblock, len, fileoff, owner).
 *
 * Note that in the actual refcnt btree we don't store the refcount < 2
 * cases because the bnobt tells us which blocks are free; single-use
 * blocks aren't recorded in the bnobt or the refcntbt.  If the rmapbt
 * supports storing multiple entries covering a given block we could
 * theoretically dispense with the refcntbt and simply count rmaps, but
 * that's inefficient in the (hot) write path, so we'll take the cost of
 * the extra tree to save time.  Also there's no guarantee that rmap
 * will be enabled.
 *
 * Given an array of rmaps sorted by physical block number, a starting
 * physical block (sp), a bag to hold rmaps that cover sp, and the next
 * physical block where the level changes (np), we can reconstruct the
 * rt refcount btree as follows:
 *
 * While there are still unprocessed rmaps in the array,
 *  - Set sp to the physical block (pblk) of the next unprocessed rmap.
 *  - Add to the bag all rmaps in the array where startblock == sp.
 *  - Set np to the physical block where the bag size will change.  This
 *    is the minimum of (the pblk of the next unprocessed rmap) and
 *    (startblock + len of each rmap in the bag).
 *  - Record the bag size as old_bag_size.
 *
 *  - While the bag isn't empty,
 *     - Remove from the bag all rmaps where startblock + len == np.
 *     - Add to the bag all rmaps in the array where startblock == np.
 *     - If the bag size isn't old_bag_size, store the refcount entry
 *       (sp, np - sp, bag_size) in the refcnt btree.
 *     - If the bag is empty, break out of the inner loop.
 *     - Set old_bag_size to the bag size
 *     - Set sp = np.
 *     - Set np to the physical block where the bag size will change.
 *       This is the minimum of (the pblk of the next unprocessed rmap)
 *       and (startblock + len of each rmap in the bag).
 *
 * Like all the other repairers, we make a list of all the refcount
 * records we need, then reinitialize the rt refcount btree root and
 * insert all the records.
 */

struct xrep_rtrefc {
	/* refcount extents */
	struct xfarray		*refcount_records;

	/* new refcountbt information */
	struct xrep_newbt	new_btree;

	/* old refcountbt blocks */
	struct xfsb_bitmap	old_rtrefcountbt_blocks;

	struct xfs_scrub	*sc;

	/* get_records()'s position in the rt refcount record array. */
	xfarray_idx_t		array_cur;

	/* # of refcountbt blocks */
	xfs_filblks_t		btblocks;
};

/* Set us up to repair refcount btrees. */
int
xrep_setup_rtrefcountbt(
	struct xfs_scrub	*sc)
{
	return xrep_setup_xfbtree(sc, "realtime rmap record bag");
}

/* Check for any obvious conflicts with this shared/CoW staging extent. */
STATIC int
xrep_rtrefc_check_ext(
	struct xfs_scrub		*sc,
	const struct xfs_refcount_irec	*rec)
{
	xfs_rgblock_t			last;

	if (xfs_rtrefcount_check_irec(sc->sr.rtg, rec) != NULL)
		return -EFSCORRUPTED;

	if (xfs_rgbno_to_rtxoff(sc->mp, rec->rc_startblock) != 0)
		return -EFSCORRUPTED;

	last = rec->rc_startblock + rec->rc_blockcount - 1;
	if (xfs_rgbno_to_rtxoff(sc->mp, last) != sc->mp->m_sb.sb_rextsize - 1)
		return -EFSCORRUPTED;

	/* Make sure this isn't free space or misaligned. */
	return xrep_require_rtext_inuse(sc, rec->rc_startblock,
			rec->rc_blockcount);
}

/* Record a reference count extent. */
STATIC int
xrep_rtrefc_stash(
	struct xrep_rtrefc		*rr,
	enum xfs_refc_domain		domain,
	xfs_rgblock_t			bno,
	xfs_extlen_t			len,
	uint64_t			refcount)
{
	struct xfs_refcount_irec	irec = {
		.rc_startblock		= bno,
		.rc_blockcount		= len,
		.rc_refcount		= refcount,
		.rc_domain		= domain,
	};
	int				error = 0;

	if (xchk_should_terminate(rr->sc, &error))
		return error;

	irec.rc_refcount = min_t(uint64_t, XFS_REFC_REFCOUNT_MAX, refcount);

	error = xrep_rtrefc_check_ext(rr->sc, &irec);
	if (error)
		return error;

	trace_xrep_refc_found(rtg_group(rr->sc->sr.rtg), &irec);

	return xfarray_append(rr->refcount_records, &irec);
}

/* Record a CoW staging extent. */
STATIC int
xrep_rtrefc_stash_cow(
	struct xrep_rtrefc		*rr,
	xfs_rgblock_t			bno,
	xfs_extlen_t			len)
{
	return xrep_rtrefc_stash(rr, XFS_REFC_DOMAIN_COW, bno, len, 1);
}

/* Decide if an rmap could describe a shared extent. */
static inline bool
xrep_rtrefc_rmap_shareable(
	const struct xfs_rmap_irec	*rmap)
{
	/* rt metadata are never sharable */
	if (XFS_RMAP_NON_INODE_OWNER(rmap->rm_owner))
		return false;

	/* Unwritten file blocks are not shareable. */
	if (rmap->rm_flags & XFS_RMAP_UNWRITTEN)
		return false;

	return true;
}

/* Grab the next (abbreviated) rmap record from the rmapbt. */
STATIC int
xrep_rtrefc_walk_rmaps(
	struct xrep_rtrefc	*rr,
	struct xfs_rmap_irec	*rmap,
	bool			*have_rec)
{
	struct xfs_btree_cur	*cur = rr->sc->sr.rmap_cur;
	struct xfs_mount	*mp = cur->bc_mp;
	int			have_gt;
	int			error = 0;

	*have_rec = false;

	/*
	 * Loop through the remaining rmaps.  Remember CoW staging
	 * extents and the refcountbt blocks from the old tree for later
	 * disposal.  We can only share written data fork extents, so
	 * keep looping until we find an rmap for one.
	 */
	do {
		if (xchk_should_terminate(rr->sc, &error))
			return error;

		error = xfs_btree_increment(cur, 0, &have_gt);
		if (error)
			return error;
		if (!have_gt)
			return 0;

		error = xfs_rmap_get_rec(cur, rmap, &have_gt);
		if (error)
			return error;
		if (XFS_IS_CORRUPT(mp, !have_gt)) {
			xfs_btree_mark_sick(cur);
			return -EFSCORRUPTED;
		}

		if (rmap->rm_owner == XFS_RMAP_OWN_COW) {
			error = xrep_rtrefc_stash_cow(rr, rmap->rm_startblock,
					rmap->rm_blockcount);
			if (error)
				return error;
		} else if (xfs_is_sb_inum(mp, rmap->rm_owner) ||
			   (rmap->rm_flags & (XFS_RMAP_ATTR_FORK |
					      XFS_RMAP_BMBT_BLOCK))) {
			xfs_btree_mark_sick(cur);
			return -EFSCORRUPTED;
		}
	} while (!xrep_rtrefc_rmap_shareable(rmap));

	*have_rec = true;
	return 0;
}

static inline uint32_t
xrep_rtrefc_encode_startblock(
	const struct xfs_refcount_irec	*irec)
{
	uint32_t			start;

	start = irec->rc_startblock & ~XFS_REFC_COWFLAG;
	if (irec->rc_domain == XFS_REFC_DOMAIN_COW)
		start |= XFS_REFC_COWFLAG;

	return start;
}

/*
 * Compare two refcount records.  We want to sort in order of increasing block
 * number.
 */
static int
xrep_rtrefc_extent_cmp(
	const void			*a,
	const void			*b)
{
	const struct xfs_refcount_irec	*ap = a;
	const struct xfs_refcount_irec	*bp = b;
	uint32_t			sa, sb;

	sa = xrep_rtrefc_encode_startblock(ap);
	sb = xrep_rtrefc_encode_startblock(bp);

	if (sa > sb)
		return 1;
	if (sa < sb)
		return -1;
	return 0;
}

/*
 * Sort the refcount extents by startblock or else the btree records will be in
 * the wrong order.  Make sure the records do not overlap in physical space.
 */
STATIC int
xrep_rtrefc_sort_records(
	struct xrep_rtrefc		*rr)
{
	struct xfs_refcount_irec	irec;
	xfarray_idx_t			cur;
	enum xfs_refc_domain		dom = XFS_REFC_DOMAIN_SHARED;
	xfs_rgblock_t			next_rgbno = 0;
	int				error;

	error = xfarray_sort(rr->refcount_records, xrep_rtrefc_extent_cmp,
			XFARRAY_SORT_KILLABLE);
	if (error)
		return error;

	foreach_xfarray_idx(rr->refcount_records, cur) {
		if (xchk_should_terminate(rr->sc, &error))
			return error;

		error = xfarray_load(rr->refcount_records, cur, &irec);
		if (error)
			return error;

		if (dom == XFS_REFC_DOMAIN_SHARED &&
		    irec.rc_domain == XFS_REFC_DOMAIN_COW) {
			dom = irec.rc_domain;
			next_rgbno = 0;
		}

		if (dom != irec.rc_domain)
			return -EFSCORRUPTED;
		if (irec.rc_startblock < next_rgbno)
			return -EFSCORRUPTED;

		next_rgbno = irec.rc_startblock + irec.rc_blockcount;
	}

	return error;
}

/* Record extents that belong to the realtime refcount inode. */
STATIC int
xrep_rtrefc_walk_rmap(
	struct xfs_btree_cur		*cur,
	const struct xfs_rmap_irec	*rec,
	void				*priv)
{
	struct xrep_rtrefc		*rr = priv;
	int				error = 0;

	if (xchk_should_terminate(rr->sc, &error))
		return error;

	/* Skip extents which are not owned by this inode and fork. */
	if (rec->rm_owner != I_INO(rr->sc->ip))
		return 0;

	error = xrep_check_ino_btree_mapping(rr->sc, rec);
	if (error)
		return error;

	return xfsb_bitmap_set(&rr->old_rtrefcountbt_blocks,
			xfs_gbno_to_fsb(cur->bc_group, rec->rm_startblock),
			rec->rm_blockcount);
}

/*
 * Walk forward through the rmap btree to collect all rmaps starting at
 * @bno in @rmap_bag.  These represent the file(s) that share ownership of
 * the current block.  Upon return, the rmap cursor points to the last record
 * satisfying the startblock constraint.
 */
static int
xrep_rtrefc_push_rmaps_at(
	struct xrep_rtrefc	*rr,
	struct rcbag		*rcstack,
	xfs_rgblock_t		bno,
	struct xfs_rmap_irec	*rmap,
	bool			*have)
{
	struct xfs_scrub	*sc = rr->sc;
	int			have_gt;
	int			error;

	while (*have && rmap->rm_startblock == bno) {
		error = rcbag_add(rcstack, rr->sc->tp, rmap);
		if (error)
			return error;

		error = xrep_rtrefc_walk_rmaps(rr, rmap, have);
		if (error)
			return error;
	}

	error = xfs_btree_decrement(sc->sr.rmap_cur, 0, &have_gt);
	if (error)
		return error;
	if (XFS_IS_CORRUPT(sc->mp, !have_gt)) {
		xfs_btree_mark_sick(sc->sr.rmap_cur);
		return -EFSCORRUPTED;
	}

	return 0;
}

/* Scan one AG for reverse mappings for the realtime refcount btree. */
STATIC int
xrep_rtrefc_scan_ag(
	struct xrep_rtrefc	*rr,
	struct xfs_perag	*pag)
{
	struct xfs_scrub	*sc = rr->sc;
	int			error;

	error = xrep_ag_init(sc, pag, &sc->sa);
	if (error)
		return error;

	error = xfs_rmap_query_all(sc->sa.rmap_cur, xrep_rtrefc_walk_rmap, rr);
	xchk_ag_free(sc, &sc->sa);
	return error;
}

/* Iterate all the rmap records to generate reference count data. */
STATIC int
xrep_rtrefc_find_refcounts(
	struct xrep_rtrefc	*rr)
{
	struct xfs_scrub	*sc = rr->sc;
	struct rcbag		*rcstack;
	struct xfs_perag	*pag = NULL;
	uint64_t		old_stack_height;
	xfs_rgblock_t		sbno;
	xfs_rgblock_t		cbno;
	xfs_rgblock_t		nbno;
	bool			have;
	int			error;

	/* Scan for old rtrefc btree blocks. */
	while ((pag = xfs_perag_next(sc->mp, pag))) {
		error = xrep_rtrefc_scan_ag(rr, pag);
		if (error) {
			xfs_perag_rele(pag);
			return error;
		}
	}

	xrep_rtgroup_btcur_init(sc, &sc->sr);

	/*
	 * Set up a bag to store all the rmap records that we're tracking to
	 * generate a reference count record.  If this exceeds
	 * XFS_REFC_REFCOUNT_MAX, we clamp rc_refcount.
	 */
	error = rcbag_init(sc->mp, sc->xmbtp, &rcstack);
	if (error)
		goto out_cur;

	/* Start the rtrmapbt cursor to the left of all records. */
	error = xfs_btree_goto_left_edge(sc->sr.rmap_cur);
	if (error)
		goto out_bag;

	/* Process reverse mappings into refcount data. */
	while (xfs_btree_has_more_records(sc->sr.rmap_cur)) {
		struct xfs_rmap_irec	rmap;

		/* Push all rmaps with pblk == sbno onto the stack */
		error = xrep_rtrefc_walk_rmaps(rr, &rmap, &have);
		if (error)
			goto out_bag;
		if (!have)
			break;
		sbno = cbno = rmap.rm_startblock;
		error = xrep_rtrefc_push_rmaps_at(rr, rcstack, sbno, &rmap,
				&have);
		if (error)
			goto out_bag;

		/* Set nbno to the bno of the next refcount change */
		error = rcbag_next_edge(rcstack, sc->tp, &rmap, have, &nbno);
		if (error)
			goto out_bag;

		ASSERT(nbno > sbno);
		old_stack_height = rcbag_count(rcstack);

		/* While stack isn't empty... */
		while (rcbag_count(rcstack) > 0) {
			/* Pop all rmaps that end at nbno */
			error = rcbag_remove_ending_at(rcstack, sc->tp, nbno);
			if (error)
				goto out_bag;

			/* Push array items that start at nbno */
			error = xrep_rtrefc_walk_rmaps(rr, &rmap, &have);
			if (error)
				goto out_bag;
			if (have) {
				error = xrep_rtrefc_push_rmaps_at(rr, rcstack,
						nbno, &rmap, &have);
				if (error)
					goto out_bag;
			}

			/* Emit refcount if necessary */
			ASSERT(nbno > cbno);
			if (rcbag_count(rcstack) != old_stack_height) {
				if (old_stack_height > 1) {
					error = xrep_rtrefc_stash(rr,
							XFS_REFC_DOMAIN_SHARED,
							cbno, nbno - cbno,
							old_stack_height);
					if (error)
						goto out_bag;
				}
				cbno = nbno;
			}

			/* Stack empty, go find the next rmap */
			if (rcbag_count(rcstack) == 0)
				break;
			old_stack_height = rcbag_count(rcstack);
			sbno = nbno;

			/* Set nbno to the bno of the next refcount change */
			error = rcbag_next_edge(rcstack, sc->tp, &rmap, have,
					&nbno);
			if (error)
				goto out_bag;

			ASSERT(nbno > sbno);
		}
	}

	ASSERT(rcbag_count(rcstack) == 0);
out_bag:
	rcbag_free(&rcstack);
out_cur:
	xchk_rtgroup_btcur_free(&sc->sr);
	return error;
}

/* Retrieve refcountbt data for bulk load. */
STATIC int
xrep_rtrefc_get_records(
	struct xfs_btree_cur		*cur,
	unsigned int			idx,
	struct xfs_btree_block		*block,
	unsigned int			nr_wanted,
	void				*priv)
{
	struct xrep_rtrefc		*rr = priv;
	union xfs_btree_rec		*block_rec;
	unsigned int			loaded;
	int				error;

	for (loaded = 0; loaded < nr_wanted; loaded++, idx++) {
		error = xfarray_load(rr->refcount_records, rr->array_cur++,
				&cur->bc_rec.rc);
		if (error)
			return error;

		block_rec = xfs_btree_rec_addr(cur, idx, block);
		cur->bc_ops->init_rec_from_cur(cur, block_rec);
	}

	return loaded;
}

/* Feed one of the new btree blocks to the bulk loader. */
STATIC int
xrep_rtrefc_claim_block(
	struct xfs_btree_cur	*cur,
	union xfs_btree_ptr	*ptr,
	void			*priv)
{
	struct xrep_rtrefc	*rr = priv;

	return xrep_newbt_claim_block(cur, &rr->new_btree, ptr);
}

/* Figure out how much space we need to create the incore btree root block. */
STATIC size_t
xrep_rtrefc_iroot_size(
	struct xfs_btree_cur	*cur,
	unsigned int		level,
	unsigned int		nr_this_level,
	void			*priv)
{
	return xfs_rtrefcount_broot_space_calc(cur->bc_mp, level,
			nr_this_level);
}

/*
 * Use the collected refcount information to stage a new rt refcount btree.  If
 * this is successful we'll return with the new btree root information logged
 * to the repair transaction but not yet committed.
 */
STATIC int
xrep_rtrefc_build_new_tree(
	struct xrep_rtrefc	*rr)
{
	struct xfs_scrub	*sc = rr->sc;
	struct xfs_rtgroup	*rtg = sc->sr.rtg;
	struct xfs_btree_cur	*refc_cur;
	int			error;

	error = xrep_rtrefc_sort_records(rr);
	if (error)
		return error;

	/*
	 * Prepare to construct the new btree by reserving disk space for the
	 * new btree and setting up all the accounting information we'll need
	 * to root the new btree while it's under construction and before we
	 * attach it to the realtime refcount inode.
	 */
	error = xrep_newbt_init_metadir_inode(&rr->new_btree, sc);
	if (error)
		return error;

	rr->new_btree.bload.get_records = xrep_rtrefc_get_records;
	rr->new_btree.bload.claim_block = xrep_rtrefc_claim_block;
	rr->new_btree.bload.iroot_size = xrep_rtrefc_iroot_size;

	refc_cur = xfs_rtrefcountbt_init_cursor(NULL, rtg);
	xfs_btree_stage_ifakeroot(refc_cur, &rr->new_btree.ifake);

	/* Compute how many blocks we'll need. */
	error = xfs_btree_bload_compute_geometry(refc_cur, &rr->new_btree.bload,
			xfarray_length(rr->refcount_records));
	if (error)
		goto err_cur;

	/* Last chance to abort before we start committing fixes. */
	if (xchk_should_terminate(sc, &error))
		goto err_cur;

	/*
	 * Guess how many blocks we're going to need to rebuild an entire
	 * rtrefcountbt from the number of extents we found, and pump up our
	 * transaction to have sufficient block reservation.  We're allowed
	 * to exceed quota to repair inconsistent metadata, though this is
	 * unlikely.
	 */
	error = xfs_trans_reserve_more_inode(sc->tp, rtg_refcount(rtg),
			rr->new_btree.bload.nr_blocks, 0, true);
	if (error)
		goto err_cur;

	/* Reserve the space we'll need for the new btree. */
	error = xrep_newbt_alloc_blocks(&rr->new_btree,
			rr->new_btree.bload.nr_blocks);
	if (error)
		goto err_cur;

	/* Add all observed refcount records. */
	rr->new_btree.ifake.if_fork->if_format = XFS_DINODE_FMT_META_BTREE;
	rr->array_cur = XFARRAY_CURSOR_INIT;
	error = xfs_btree_bload(refc_cur, &rr->new_btree.bload, rr);
	if (error)
		goto err_cur;

	/*
	 * Install the new rtrefc btree in the inode.  After this point the old
	 * btree is no longer accessible, the new tree is live, and we can
	 * delete the cursor.
	 */
	xfs_rtrefcountbt_commit_staged_btree(refc_cur, sc->tp);
	xrep_inode_set_nblocks(rr->sc, rr->new_btree.ifake.if_blocks);
	xfs_btree_del_cursor(refc_cur, 0);

	/* Dispose of any unused blocks and the accounting information. */
	error = xrep_newbt_commit(&rr->new_btree);
	if (error)
		return error;

	return xrep_roll_trans(sc);
err_cur:
	xfs_btree_del_cursor(refc_cur, error);
	xrep_newbt_cancel(&rr->new_btree);
	return error;
}

/* Rebuild the rt refcount btree. */
int
xrep_rtrefcountbt(
	struct xfs_scrub	*sc)
{
	struct xrep_rtrefc	*rr;
	struct xfs_mount	*mp = sc->mp;
	int			error;

	/* We require the rmapbt to rebuild anything. */
	if (!xfs_has_rtrmapbt(mp))
		return -EOPNOTSUPP;

	/* Make sure any problems with the fork are fixed. */
	error = xrep_metadata_inode_forks(sc);
	if (error)
		return error;

	rr = kzalloc_obj(struct xrep_rtrefc, XCHK_GFP_FLAGS);
	if (!rr)
		return -ENOMEM;
	rr->sc = sc;

	/* Set up enough storage to handle one refcount record per rt extent. */
	error = xfarray_create("realtime reference count records",
			mp->m_sb.sb_rextents, sizeof(struct xfs_refcount_irec),
			&rr->refcount_records);
	if (error)
		goto out_rr;

	/* Collect all reference counts. */
	xfsb_bitmap_init(&rr->old_rtrefcountbt_blocks);
	error = xrep_rtrefc_find_refcounts(rr);
	if (error)
		goto out_bitmap;

	xfs_trans_ijoin(sc->tp, sc->ip, 0);

	/* Rebuild the refcount information. */
	error = xrep_rtrefc_build_new_tree(rr);
	if (error)
		goto out_bitmap;

	/*
	 * Free all the extents that were allocated to the former rtrefcountbt
	 * and aren't cross-linked with something else.
	 */
	error = xrep_reap_metadir_fsblocks(rr->sc,
			&rr->old_rtrefcountbt_blocks);
	if (error)
		goto out_bitmap;

out_bitmap:
	xfsb_bitmap_destroy(&rr->old_rtrefcountbt_blocks);
	xfarray_destroy(rr->refcount_records);
out_rr:
	kfree(rr);
	return error;
}