// SPDX-License-Identifier: GPL-2.0-or-later /* * Copyright (C) 2022-2023 Oracle. All Rights Reserved. * Author: Darrick J. Wong */ #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_log_format.h" #include "xfs_trans.h" #include "xfs_sb.h" #include "xfs_inode.h" #include "xfs_alloc.h" #include "xfs_alloc_btree.h" #include "xfs_ialloc.h" #include "xfs_ialloc_btree.h" #include "xfs_rmap.h" #include "xfs_rmap_btree.h" #include "xfs_refcount.h" #include "xfs_refcount_btree.h" #include "xfs_extent_busy.h" #include "xfs_ag.h" #include "xfs_ag_resv.h" #include "xfs_quota.h" #include "xfs_qm.h" #include "xfs_bmap.h" #include "xfs_da_format.h" #include "xfs_da_btree.h" #include "xfs_attr.h" #include "xfs_attr_remote.h" #include "xfs_defer.h" #include "xfs_metafile.h" #include "xfs_rtgroup.h" #include "xfs_rtrmap_btree.h" #include "xfs_extfree_item.h" #include "xfs_rmap_item.h" #include "xfs_refcount_item.h" #include "xfs_buf_item.h" #include "xfs_bmap_item.h" #include "xfs_bmap_btree.h" #include "scrub/scrub.h" #include "scrub/common.h" #include "scrub/trace.h" #include "scrub/repair.h" #include "scrub/bitmap.h" #include "scrub/agb_bitmap.h" #include "scrub/fsb_bitmap.h" #include "scrub/rtb_bitmap.h" #include "scrub/reap.h" /* * Disposal of Blocks from Old Metadata * * Now that we've constructed a new btree to replace the damaged one, we want * to dispose of the blocks that (we think) the old btree was using. * Previously, we used the rmapbt to collect the extents (bitmap) with the * rmap owner corresponding to the tree we rebuilt, collected extents for any * blocks with the same rmap owner that are owned by another data structure * (sublist), and subtracted sublist from bitmap. In theory the extents * remaining in bitmap are the old btree's blocks. * * Unfortunately, it's possible that the btree was crosslinked with other * blocks on disk. The rmap data can tell us if there are multiple owners, so * if the rmapbt says there is an owner of this block other than @oinfo, then * the block is crosslinked. Remove the reverse mapping and continue. * * If there is one rmap record, we can free the block, which removes the * reverse mapping but doesn't add the block to the free space. Our repair * strategy is to hope the other metadata objects crosslinked on this block * will be rebuilt (atop different blocks), thereby removing all the cross * links. * * If there are no rmap records at all, we also free the block. If the btree * being rebuilt lives in the free space (bnobt/cntbt/rmapbt) then there isn't * supposed to be a rmap record and everything is ok. For other btrees there * had to have been an rmap entry for the block to have ended up on @bitmap, * so if it's gone now there's something wrong and the fs will shut down. * * Note: If there are multiple rmap records with only the same rmap owner as * the btree we're trying to rebuild and the block is indeed owned by another * data structure with the same rmap owner, then the block will be in sublist * and therefore doesn't need disposal. If there are multiple rmap records * with only the same rmap owner but the block is not owned by something with * the same rmap owner, the block will be freed. * * The caller is responsible for locking the AG headers/inode for the entire * rebuild operation so that nothing else can sneak in and change the incore * state while we're not looking. We must also invalidate any buffers * associated with @bitmap. */ /* Information about reaping extents after a repair. */ struct xreap_state { struct xfs_scrub *sc; union { struct { /* * For AG blocks, this is reverse mapping owner and * metadata reservation type. */ const struct xfs_owner_info *oinfo; enum xfs_ag_resv_type resv; }; struct { /* For file blocks, this is the inode and fork. */ struct xfs_inode *ip; int whichfork; }; }; /* Number of invalidated buffers logged to the current transaction. */ unsigned int nr_binval; /* Maximum number of buffers we can invalidate in a single tx. */ unsigned int max_binval; /* Number of deferred reaps attached to the current transaction. */ unsigned int nr_deferred; /* Maximum number of intents we can reap in a single transaction. */ unsigned int max_deferred; }; /* Put a block back on the AGFL. */ STATIC int xreap_put_freelist( struct xfs_scrub *sc, xfs_agblock_t agbno) { struct xfs_buf *agfl_bp; int error; /* Make sure there's space on the freelist. */ error = xrep_fix_freelist(sc, 0); if (error) return error; /* * Since we're "freeing" a lost block onto the AGFL, we have to * create an rmap for the block prior to merging it or else other * parts will break. */ error = xfs_rmap_alloc(sc->tp, sc->sa.agf_bp, sc->sa.pag, agbno, 1, &XFS_RMAP_OINFO_AG); if (error) return error; /* Put the block on the AGFL. */ error = xfs_alloc_read_agfl(sc->sa.pag, sc->tp, &agfl_bp); if (error) return error; error = xfs_alloc_put_freelist(sc->sa.pag, sc->tp, sc->sa.agf_bp, agfl_bp, agbno, 0); if (error) return error; xfs_extent_busy_insert(sc->tp, pag_group(sc->sa.pag), agbno, 1, XFS_EXTENT_BUSY_SKIP_DISCARD); return 0; } /* Are there any uncommitted reap operations? */ static inline bool xreap_is_dirty(const struct xreap_state *rs) { return rs->nr_binval > 0 || rs->nr_deferred > 0; } /* * Decide if we need to roll the transaction to clear out the the log * reservation that we allocated to buffer invalidations. */ static inline bool xreap_want_binval_roll(const struct xreap_state *rs) { return rs->nr_binval >= rs->max_binval; } /* Reset the buffer invalidation count after rolling. */ static inline void xreap_binval_reset(struct xreap_state *rs) { rs->nr_binval = 0; } /* * Bump the number of invalidated buffers, and return true if we can continue, * or false if we need to roll the transaction. */ static inline bool xreap_inc_binval(struct xreap_state *rs) { rs->nr_binval++; return rs->nr_binval < rs->max_binval; } /* * Decide if we want to finish the deferred ops that are attached to the scrub * transaction. We don't want to queue huge chains of deferred ops because * that can consume a lot of log space and kernel memory. Hence we trigger a * xfs_defer_finish if there are too many deferred reap operations or we've run * out of space for invalidations. */ static inline bool xreap_want_defer_finish(const struct xreap_state *rs) { return rs->nr_deferred >= rs->max_deferred; } /* * Reset the defer chain length and buffer invalidation count after finishing * items. */ static inline void xreap_defer_finish_reset(struct xreap_state *rs) { rs->nr_deferred = 0; rs->nr_binval = 0; } /* * Bump the number of deferred extent reaps. */ static inline void xreap_inc_defer(struct xreap_state *rs) { rs->nr_deferred++; } /* Force the caller to finish a deferred item chain. */ static inline void xreap_force_defer_finish(struct xreap_state *rs) { rs->nr_deferred = rs->max_deferred; } /* Maximum number of fsblocks that we might find in a buffer to invalidate. */ static inline unsigned int xrep_binval_max_fsblocks( struct xfs_mount *mp) { /* Remote xattr values are the largest buffers that we support. */ return xfs_attr3_max_rmt_blocks(mp); } /* * Compute the maximum length of a buffer cache scan (in units of sectors), * given a quantity of fs blocks. */ xfs_daddr_t xrep_bufscan_max_sectors( struct xfs_mount *mp, xfs_extlen_t fsblocks) { return XFS_FSB_TO_BB(mp, min_t(xfs_extlen_t, fsblocks, xrep_binval_max_fsblocks(mp))); } /* * Return an incore buffer from a sector scan, or NULL if there are no buffers * left to return. */ struct xfs_buf * xrep_bufscan_advance( struct xfs_mount *mp, struct xrep_bufscan *scan) { scan->__sector_count += scan->daddr_step; while (scan->__sector_count <= scan->max_sectors) { struct xfs_buf *bp = NULL; int error; error = xfs_buf_incore(mp->m_ddev_targp, scan->daddr, scan->__sector_count, XBF_LIVESCAN, &bp); if (!error) return bp; scan->__sector_count += scan->daddr_step; } return NULL; } /* Try to invalidate the incore buffers for an extent that we're freeing. */ STATIC void xreap_agextent_binval( struct xreap_state *rs, xfs_agblock_t agbno, xfs_extlen_t *aglenp) { struct xfs_scrub *sc = rs->sc; struct xfs_perag *pag = sc->sa.pag; struct xfs_mount *mp = sc->mp; xfs_agblock_t agbno_next = agbno + *aglenp; xfs_agblock_t bno = agbno; /* * Avoid invalidating AG headers and post-EOFS blocks because we never * own those. */ if (!xfs_verify_agbno(pag, agbno) || !xfs_verify_agbno(pag, agbno_next - 1)) return; /* * If there are incore buffers for these blocks, invalidate them. We * assume that the lack of any other known owners means that the buffer * can be locked without risk of deadlocking. The buffer cache cannot * detect aliasing, so employ nested loops to scan for incore buffers * of any plausible size. */ while (bno < agbno_next) { struct xrep_bufscan scan = { .daddr = xfs_agbno_to_daddr(pag, bno), .max_sectors = xrep_bufscan_max_sectors(mp, agbno_next - bno), .daddr_step = XFS_FSB_TO_BB(mp, 1), }; struct xfs_buf *bp; while ((bp = xrep_bufscan_advance(mp, &scan)) != NULL) { xfs_trans_bjoin(sc->tp, bp); xfs_trans_binval(sc->tp, bp); /* * Stop invalidating if we've hit the limit; we should * still have enough reservation left to free however * far we've gotten. */ if (!xreap_inc_binval(rs)) { *aglenp -= agbno_next - bno; goto out; } } bno++; } out: trace_xreap_agextent_binval(pag_group(sc->sa.pag), agbno, *aglenp); } /* * Figure out the longest run of blocks that we can dispose of with a single * call. Cross-linked blocks should have their reverse mappings removed, but * single-owner extents can be freed. AGFL blocks can only be put back one at * a time. */ STATIC int xreap_agextent_select( struct xreap_state *rs, xfs_agblock_t agbno, xfs_agblock_t agbno_next, bool *crosslinked, xfs_extlen_t *aglenp) { struct xfs_scrub *sc = rs->sc; struct xfs_btree_cur *cur; xfs_agblock_t bno = agbno + 1; xfs_extlen_t len = 1; int error; /* * Determine if there are any other rmap records covering the first * block of this extent. If so, the block is crosslinked. */ cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, sc->sa.agf_bp, sc->sa.pag); error = xfs_rmap_has_other_keys(cur, agbno, 1, rs->oinfo, crosslinked); if (error) goto out_cur; /* AGFL blocks can only be deal with one at a time. */ if (rs->resv == XFS_AG_RESV_AGFL) goto out_found; /* * Figure out how many of the subsequent blocks have the same crosslink * status. */ while (bno < agbno_next) { bool also_crosslinked; error = xfs_rmap_has_other_keys(cur, bno, 1, rs->oinfo, &also_crosslinked); if (error) goto out_cur; if (*crosslinked != also_crosslinked) break; len++; bno++; } out_found: *aglenp = len; trace_xreap_agextent_select(pag_group(sc->sa.pag), agbno, len, *crosslinked); out_cur: xfs_btree_del_cursor(cur, error); return error; } /* * Dispose of as much of the beginning of this AG extent as possible. The * number of blocks disposed of will be returned in @aglenp. */ STATIC int xreap_agextent_iter( struct xreap_state *rs, xfs_agblock_t agbno, xfs_extlen_t *aglenp, bool crosslinked) { struct xfs_scrub *sc = rs->sc; xfs_fsblock_t fsbno; int error = 0; ASSERT(rs->resv != XFS_AG_RESV_METAFILE); fsbno = xfs_agbno_to_fsb(sc->sa.pag, agbno); /* * If there are other rmappings, this block is cross linked and must * not be freed. Remove the reverse mapping and move on. Otherwise, * we were the only owner of the block, so free the extent, which will * also remove the rmap. * * XXX: XFS doesn't support detecting the case where a single block * metadata structure is crosslinked with a multi-block structure * because the buffer cache doesn't detect aliasing problems, so we * can't fix 100% of crosslinking problems (yet). The verifiers will * blow on writeout, the filesystem will shut down, and the admin gets * to run xfs_repair. */ if (crosslinked) { trace_xreap_dispose_unmap_extent(pag_group(sc->sa.pag), agbno, *aglenp); if (rs->oinfo == &XFS_RMAP_OINFO_COW) { /* * t0: Unmapping CoW staging extents, remove the * records from the refcountbt, which will remove the * rmap record as well. */ xfs_refcount_free_cow_extent(sc->tp, false, fsbno, *aglenp); xreap_inc_defer(rs); return 0; } /* t1: unmap crosslinked metadata blocks */ xfs_rmap_free_extent(sc->tp, false, fsbno, *aglenp, rs->oinfo->oi_owner); xreap_inc_defer(rs); return 0; } trace_xreap_dispose_free_extent(pag_group(sc->sa.pag), agbno, *aglenp); /* * Invalidate as many buffers as we can, starting at agbno. If this * function sets *aglenp to zero, the transaction is full of logged * buffer invalidations, so we need to return early so that we can * roll and retry. */ xreap_agextent_binval(rs, agbno, aglenp); if (*aglenp == 0) { ASSERT(xreap_want_binval_roll(rs)); return 0; } /* * t2: To get rid of CoW staging extents, use deferred work items * to remove the refcountbt records (which removes the rmap records) * and free the extent. We're not worried about the system going down * here because log recovery walks the refcount btree to clean out the * CoW staging extents. */ if (rs->oinfo == &XFS_RMAP_OINFO_COW) { ASSERT(rs->resv == XFS_AG_RESV_NONE); xfs_refcount_free_cow_extent(sc->tp, false, fsbno, *aglenp); error = xfs_free_extent_later(sc->tp, fsbno, *aglenp, NULL, rs->resv, XFS_FREE_EXTENT_SKIP_DISCARD); if (error) return error; xreap_inc_defer(rs); return 0; } /* t3: Put blocks back on the AGFL one at a time. */ if (rs->resv == XFS_AG_RESV_AGFL) { ASSERT(*aglenp == 1); error = xreap_put_freelist(sc, agbno); if (error) return error; xreap_force_defer_finish(rs); return 0; } /* * t4: Use deferred frees to get rid of the old btree blocks to try to * minimize the window in which we could crash and lose the old blocks. * Add a defer ops barrier every other extent to avoid stressing the * system with large EFIs. */ error = xfs_free_extent_later(sc->tp, fsbno, *aglenp, rs->oinfo, rs->resv, XFS_FREE_EXTENT_SKIP_DISCARD); if (error) return error; xreap_inc_defer(rs); if (rs->nr_deferred % 2 == 0) xfs_defer_add_barrier(sc->tp); return 0; } /* Configure the deferral and invalidation limits */ static inline void xreap_configure_limits( struct xreap_state *rs, unsigned int fixed_overhead, unsigned int variable_overhead, unsigned int per_intent, unsigned int per_binval) { struct xfs_scrub *sc = rs->sc; unsigned int res = sc->tp->t_log_res - fixed_overhead; /* Don't underflow the reservation */ if (sc->tp->t_log_res < (fixed_overhead + variable_overhead)) { ASSERT(sc->tp->t_log_res >= (fixed_overhead + variable_overhead)); xfs_force_shutdown(sc->mp, SHUTDOWN_CORRUPT_INCORE); return; } rs->max_deferred = per_intent ? res / variable_overhead : 0; res -= rs->max_deferred * per_intent; rs->max_binval = per_binval ? res / per_binval : 0; } /* * Compute the maximum number of intent items that reaping can attach to the * scrub transaction given the worst case log overhead of the intent items * needed to reap a single per-AG space extent. This is not for freeing CoW * staging extents. */ STATIC void xreap_configure_agextent_limits( struct xreap_state *rs) { struct xfs_scrub *sc = rs->sc; struct xfs_mount *mp = sc->mp; /* * In the worst case, relogging an intent item causes both an intent * item and a done item to be attached to a transaction for each extent * that we'd like to process. */ const unsigned int efi = xfs_efi_log_space(1) + xfs_efd_log_space(1); const unsigned int rui = xfs_rui_log_space(1) + xfs_rud_log_space(); /* * Various things can happen when reaping non-CoW metadata blocks: * * t1: Unmapping crosslinked metadata blocks: deferred removal of rmap * record. * * t3: Freeing to AGFL: roll and finish deferred items for every block. * Limits here do not matter. * * t4: Freeing metadata blocks: deferred freeing of the space, which * also removes the rmap record. * * For simplicity, we'll use the worst-case intents size to determine * the maximum number of deferred extents before we have to finish the * whole chain. If we're trying to reap a btree larger than this size, * a crash midway through reaping can result in leaked blocks. */ const unsigned int t1 = rui; const unsigned int t4 = rui + efi; const unsigned int per_intent = max(t1, t4); /* * For each transaction in a reap chain, we must be able to take one * step in the defer item chain, which should only consist of EFI or * RUI items. */ const unsigned int f1 = xfs_calc_finish_efi_reservation(mp, 1); const unsigned int f2 = xfs_calc_finish_rui_reservation(mp, 1); const unsigned int step_size = max(f1, f2); /* Largest buffer size (in fsblocks) that can be invalidated. */ const unsigned int max_binval = xrep_binval_max_fsblocks(mp); /* Maximum overhead of invalidating one buffer. */ const unsigned int per_binval = xfs_buf_inval_log_space(1, XFS_B_TO_FSBT(mp, max_binval)); /* * For each transaction in a reap chain, we can delete some number of * extents and invalidate some number of blocks. We assume that btree * blocks aren't usually contiguous; and that scrub likely pulled all * the buffers into memory. From these assumptions, set the maximum * number of deferrals we can queue before flushing the defer chain, * and the number of invalidations we can queue before rolling to a * clean transaction (and possibly relogging some of the deferrals) to * the same quantity. */ const unsigned int variable_overhead = per_intent + per_binval; xreap_configure_limits(rs, step_size, variable_overhead, per_intent, per_binval); trace_xreap_agextent_limits(sc->tp, per_binval, rs->max_binval, step_size, per_intent, rs->max_deferred); } /* * Compute the maximum number of intent items that reaping can attach to the * scrub transaction given the worst case log overhead of the intent items * needed to reap a single CoW staging extent. This is not for freeing * metadata blocks. */ STATIC void xreap_configure_agcow_limits( struct xreap_state *rs) { struct xfs_scrub *sc = rs->sc; struct xfs_mount *mp = sc->mp; /* * In the worst case, relogging an intent item causes both an intent * item and a done item to be attached to a transaction for each extent * that we'd like to process. */ const unsigned int efi = xfs_efi_log_space(1) + xfs_efd_log_space(1); const unsigned int rui = xfs_rui_log_space(1) + xfs_rud_log_space(); const unsigned int cui = xfs_cui_log_space(1) + xfs_cud_log_space(); /* * Various things can happen when reaping non-CoW metadata blocks: * * t0: Unmapping crosslinked CoW blocks: deferred removal of refcount * record, which defers removal of rmap record * * t2: Freeing CoW blocks: deferred removal of refcount record, which * defers removal of rmap record; and deferred removal of the space * * For simplicity, we'll use the worst-case intents size to determine * the maximum number of deferred extents before we have to finish the * whole chain. If we're trying to reap a btree larger than this size, * a crash midway through reaping can result in leaked blocks. */ const unsigned int t0 = cui + rui; const unsigned int t2 = cui + rui + efi; const unsigned int per_intent = max(t0, t2); /* * For each transaction in a reap chain, we must be able to take one * step in the defer item chain, which should only consist of CUI, EFI, * or RUI items. */ const unsigned int f1 = xfs_calc_finish_efi_reservation(mp, 1); const unsigned int f2 = xfs_calc_finish_rui_reservation(mp, 1); const unsigned int f3 = xfs_calc_finish_cui_reservation(mp, 1); const unsigned int step_size = max3(f1, f2, f3); /* Largest buffer size (in fsblocks) that can be invalidated. */ const unsigned int max_binval = xrep_binval_max_fsblocks(mp); /* Overhead of invalidating one buffer */ const unsigned int per_binval = xfs_buf_inval_log_space(1, XFS_B_TO_FSBT(mp, max_binval)); /* * For each transaction in a reap chain, we can delete some number of * extents and invalidate some number of blocks. We assume that CoW * staging extents are usually more than 1 fsblock, and that there * shouldn't be any buffers for those blocks. From the assumptions, * set the number of deferrals to use as much of the reservation as * it can, but leave space to invalidate 1/8th that number of buffers. */ const unsigned int variable_overhead = per_intent + (per_binval / 8); xreap_configure_limits(rs, step_size, variable_overhead, per_intent, per_binval); trace_xreap_agcow_limits(sc->tp, per_binval, rs->max_binval, step_size, per_intent, rs->max_deferred); } /* * Break an AG metadata extent into sub-extents by fate (crosslinked, not * crosslinked), and dispose of each sub-extent separately. */ STATIC int xreap_agmeta_extent( uint32_t agbno, uint32_t len, void *priv) { struct xreap_state *rs = priv; struct xfs_scrub *sc = rs->sc; xfs_agblock_t agbno_next = agbno + len; int error = 0; ASSERT(len <= XFS_MAX_BMBT_EXTLEN); ASSERT(sc->ip == NULL); while (agbno < agbno_next) { xfs_extlen_t aglen; bool crosslinked; error = xreap_agextent_select(rs, agbno, agbno_next, &crosslinked, &aglen); if (error) return error; error = xreap_agextent_iter(rs, agbno, &aglen, crosslinked); if (error) return error; if (xreap_want_defer_finish(rs)) { error = xrep_defer_finish(sc); if (error) return error; xreap_defer_finish_reset(rs); } else if (xreap_want_binval_roll(rs)) { error = xrep_roll_ag_trans(sc); if (error) return error; xreap_binval_reset(rs); } agbno += aglen; } return 0; } /* Dispose of every block of every AG metadata extent in the bitmap. */ int xrep_reap_agblocks( struct xfs_scrub *sc, struct xagb_bitmap *bitmap, const struct xfs_owner_info *oinfo, enum xfs_ag_resv_type type) { struct xreap_state rs = { .sc = sc, .oinfo = oinfo, .resv = type, }; int error; ASSERT(xfs_has_rmapbt(sc->mp)); ASSERT(sc->ip == NULL); xreap_configure_agextent_limits(&rs); error = xagb_bitmap_walk(bitmap, xreap_agmeta_extent, &rs); if (error) return error; if (xreap_is_dirty(&rs)) return xrep_defer_finish(sc); return 0; } /* * Break a file metadata extent into sub-extents by fate (crosslinked, not * crosslinked), and dispose of each sub-extent separately. The extent must * not cross an AG boundary. */ STATIC int xreap_fsmeta_extent( uint64_t fsbno, uint64_t len, void *priv) { struct xreap_state *rs = priv; struct xfs_scrub *sc = rs->sc; xfs_agnumber_t agno = XFS_FSB_TO_AGNO(sc->mp, fsbno); xfs_agblock_t agbno = XFS_FSB_TO_AGBNO(sc->mp, fsbno); xfs_agblock_t agbno_next = agbno + len; int error = 0; ASSERT(len <= XFS_MAX_BMBT_EXTLEN); ASSERT(sc->ip != NULL); ASSERT(!sc->sa.pag); /* * We're reaping blocks after repairing file metadata, which means that * we have to init the xchk_ag structure ourselves. */ sc->sa.pag = xfs_perag_get(sc->mp, agno); if (!sc->sa.pag) return -EFSCORRUPTED; error = xfs_alloc_read_agf(sc->sa.pag, sc->tp, 0, &sc->sa.agf_bp); if (error) goto out_pag; while (agbno < agbno_next) { xfs_extlen_t aglen; bool crosslinked; error = xreap_agextent_select(rs, agbno, agbno_next, &crosslinked, &aglen); if (error) goto out_agf; error = xreap_agextent_iter(rs, agbno, &aglen, crosslinked); if (error) goto out_agf; if (xreap_want_defer_finish(rs)) { /* * Holds the AGF buffer across the deferred chain * processing. */ error = xrep_defer_finish(sc); if (error) goto out_agf; xreap_defer_finish_reset(rs); } else if (xreap_want_binval_roll(rs)) { /* * Hold the AGF buffer across the transaction roll so * that we don't have to reattach it to the scrub * context. */ xfs_trans_bhold(sc->tp, sc->sa.agf_bp); error = xfs_trans_roll_inode(&sc->tp, sc->ip); xfs_trans_bjoin(sc->tp, sc->sa.agf_bp); if (error) goto out_agf; xreap_binval_reset(rs); } agbno += aglen; } out_agf: xfs_trans_brelse(sc->tp, sc->sa.agf_bp); sc->sa.agf_bp = NULL; out_pag: xfs_perag_put(sc->sa.pag); sc->sa.pag = NULL; return error; } /* * Dispose of every block of every fs metadata extent in the bitmap. * Do not use this to dispose of the mappings in an ondisk inode fork. */ int xrep_reap_fsblocks( struct xfs_scrub *sc, struct xfsb_bitmap *bitmap, const struct xfs_owner_info *oinfo) { struct xreap_state rs = { .sc = sc, .oinfo = oinfo, .resv = XFS_AG_RESV_NONE, }; int error; ASSERT(xfs_has_rmapbt(sc->mp)); ASSERT(sc->ip != NULL); if (oinfo == &XFS_RMAP_OINFO_COW) xreap_configure_agcow_limits(&rs); else xreap_configure_agextent_limits(&rs); error = xfsb_bitmap_walk(bitmap, xreap_fsmeta_extent, &rs); if (error) return error; if (xreap_is_dirty(&rs)) return xrep_defer_finish(sc); return 0; } #ifdef CONFIG_XFS_RT /* * Figure out the longest run of blocks that we can dispose of with a single * call. Cross-linked blocks should have their reverse mappings removed, but * single-owner extents can be freed. Units are rt blocks, not rt extents. */ STATIC int xreap_rgextent_select( struct xreap_state *rs, xfs_rgblock_t rgbno, xfs_rgblock_t rgbno_next, bool *crosslinked, xfs_extlen_t *rglenp) { struct xfs_scrub *sc = rs->sc; struct xfs_btree_cur *cur; xfs_rgblock_t bno = rgbno + 1; xfs_extlen_t len = 1; int error; /* * Determine if there are any other rmap records covering the first * block of this extent. If so, the block is crosslinked. */ cur = xfs_rtrmapbt_init_cursor(sc->tp, sc->sr.rtg); error = xfs_rmap_has_other_keys(cur, rgbno, 1, rs->oinfo, crosslinked); if (error) goto out_cur; /* * Figure out how many of the subsequent blocks have the same crosslink * status. */ while (bno < rgbno_next) { bool also_crosslinked; error = xfs_rmap_has_other_keys(cur, bno, 1, rs->oinfo, &also_crosslinked); if (error) goto out_cur; if (*crosslinked != also_crosslinked) break; len++; bno++; } *rglenp = len; trace_xreap_agextent_select(rtg_group(sc->sr.rtg), rgbno, len, *crosslinked); out_cur: xfs_btree_del_cursor(cur, error); return error; } /* * Dispose of as much of the beginning of this rtgroup extent as possible. * The number of blocks disposed of will be returned in @rglenp. */ STATIC int xreap_rgextent_iter( struct xreap_state *rs, xfs_rgblock_t rgbno, xfs_extlen_t *rglenp, bool crosslinked) { struct xfs_scrub *sc = rs->sc; xfs_rtblock_t rtbno; int error; /* * The only caller so far is CoW fork repair, so we only know how to * unlink or free CoW staging extents. Here we don't have to worry * about invalidating buffers! */ if (rs->oinfo != &XFS_RMAP_OINFO_COW) { ASSERT(rs->oinfo == &XFS_RMAP_OINFO_COW); return -EFSCORRUPTED; } ASSERT(rs->resv == XFS_AG_RESV_NONE); rtbno = xfs_rgbno_to_rtb(sc->sr.rtg, rgbno); /* * t1: There are other rmappings; this block is cross linked and must * not be freed. Remove the forward and reverse mapping and move on. */ if (crosslinked) { trace_xreap_dispose_unmap_extent(rtg_group(sc->sr.rtg), rgbno, *rglenp); xfs_refcount_free_cow_extent(sc->tp, true, rtbno, *rglenp); xreap_inc_defer(rs); return 0; } trace_xreap_dispose_free_extent(rtg_group(sc->sr.rtg), rgbno, *rglenp); /* * t2: The CoW staging extent is not crosslinked. Use deferred work * to remove the refcountbt records (which removes the rmap records) * and free the extent. We're not worried about the system going down * here because log recovery walks the refcount btree to clean out the * CoW staging extents. */ xfs_refcount_free_cow_extent(sc->tp, true, rtbno, *rglenp); error = xfs_free_extent_later(sc->tp, rtbno, *rglenp, NULL, rs->resv, XFS_FREE_EXTENT_REALTIME | XFS_FREE_EXTENT_SKIP_DISCARD); if (error) return error; xreap_inc_defer(rs); return 0; } /* * Compute the maximum number of intent items that reaping can attach to the * scrub transaction given the worst case log overhead of the intent items * needed to reap a single CoW staging extent. This is not for freeing * metadata blocks. */ STATIC void xreap_configure_rgcow_limits( struct xreap_state *rs) { struct xfs_scrub *sc = rs->sc; struct xfs_mount *mp = sc->mp; /* * In the worst case, relogging an intent item causes both an intent * item and a done item to be attached to a transaction for each extent * that we'd like to process. */ const unsigned int efi = xfs_efi_log_space(1) + xfs_efd_log_space(1); const unsigned int rui = xfs_rui_log_space(1) + xfs_rud_log_space(); const unsigned int cui = xfs_cui_log_space(1) + xfs_cud_log_space(); /* * Various things can happen when reaping non-CoW metadata blocks: * * t1: Unmapping crosslinked CoW blocks: deferred removal of refcount * record, which defers removal of rmap record * * t2: Freeing CoW blocks: deferred removal of refcount record, which * defers removal of rmap record; and deferred removal of the space * * For simplicity, we'll use the worst-case intents size to determine * the maximum number of deferred extents before we have to finish the * whole chain. If we're trying to reap a btree larger than this size, * a crash midway through reaping can result in leaked blocks. */ const unsigned int t1 = cui + rui; const unsigned int t2 = cui + rui + efi; const unsigned int per_intent = max(t1, t2); /* * For each transaction in a reap chain, we must be able to take one * step in the defer item chain, which should only consist of CUI, EFI, * or RUI items. */ const unsigned int f1 = xfs_calc_finish_rt_efi_reservation(mp, 1); const unsigned int f2 = xfs_calc_finish_rt_rui_reservation(mp, 1); const unsigned int f3 = xfs_calc_finish_rt_cui_reservation(mp, 1); const unsigned int step_size = max3(f1, f2, f3); /* * The only buffer for the rt device is the rtgroup super, so we don't * need to save space for buffer invalidations. */ xreap_configure_limits(rs, step_size, per_intent, per_intent, 0); trace_xreap_rgcow_limits(sc->tp, 0, 0, step_size, per_intent, rs->max_deferred); } #define XREAP_RTGLOCK_ALL (XFS_RTGLOCK_BITMAP | \ XFS_RTGLOCK_RMAP | \ XFS_RTGLOCK_REFCOUNT) /* * Break a rt file metadata extent into sub-extents by fate (crosslinked, not * crosslinked), and dispose of each sub-extent separately. The extent must * be aligned to a realtime extent. */ STATIC int xreap_rtmeta_extent( uint64_t rtbno, uint64_t len, void *priv) { struct xreap_state *rs = priv; struct xfs_scrub *sc = rs->sc; xfs_rgblock_t rgbno = xfs_rtb_to_rgbno(sc->mp, rtbno); xfs_rgblock_t rgbno_next = rgbno + len; int error = 0; ASSERT(sc->ip != NULL); ASSERT(!sc->sr.rtg); /* * We're reaping blocks after repairing file metadata, which means that * we have to init the xchk_ag structure ourselves. */ sc->sr.rtg = xfs_rtgroup_get(sc->mp, xfs_rtb_to_rgno(sc->mp, rtbno)); if (!sc->sr.rtg) return -EFSCORRUPTED; xfs_rtgroup_lock(sc->sr.rtg, XREAP_RTGLOCK_ALL); while (rgbno < rgbno_next) { xfs_extlen_t rglen; bool crosslinked; error = xreap_rgextent_select(rs, rgbno, rgbno_next, &crosslinked, &rglen); if (error) goto out_unlock; error = xreap_rgextent_iter(rs, rgbno, &rglen, crosslinked); if (error) goto out_unlock; if (xreap_want_defer_finish(rs)) { error = xfs_defer_finish(&sc->tp); if (error) goto out_unlock; xreap_defer_finish_reset(rs); } else if (xreap_want_binval_roll(rs)) { error = xfs_trans_roll_inode(&sc->tp, sc->ip); if (error) goto out_unlock; xreap_binval_reset(rs); } rgbno += rglen; } out_unlock: xfs_rtgroup_unlock(sc->sr.rtg, XREAP_RTGLOCK_ALL); xfs_rtgroup_put(sc->sr.rtg); sc->sr.rtg = NULL; return error; } /* * Dispose of every block of every rt metadata extent in the bitmap. * Do not use this to dispose of the mappings in an ondisk inode fork. */ int xrep_reap_rtblocks( struct xfs_scrub *sc, struct xrtb_bitmap *bitmap, const struct xfs_owner_info *oinfo) { struct xreap_state rs = { .sc = sc, .oinfo = oinfo, .resv = XFS_AG_RESV_NONE, }; int error; ASSERT(xfs_has_rmapbt(sc->mp)); ASSERT(sc->ip != NULL); ASSERT(oinfo == &XFS_RMAP_OINFO_COW); xreap_configure_rgcow_limits(&rs); error = xrtb_bitmap_walk(bitmap, xreap_rtmeta_extent, &rs); if (error) return error; if (xreap_is_dirty(&rs)) return xrep_defer_finish(sc); return 0; } #endif /* CONFIG_XFS_RT */ /* * Dispose of every block of an old metadata btree that used to be rooted in a * metadata directory file. */ int xrep_reap_metadir_fsblocks( struct xfs_scrub *sc, struct xfsb_bitmap *bitmap) { /* * Reap old metadir btree blocks with XFS_AG_RESV_NONE because the old * blocks are no longer mapped by the inode, and inode metadata space * reservations can only account freed space to the i_nblocks. */ struct xfs_owner_info oinfo; struct xreap_state rs = { .sc = sc, .oinfo = &oinfo, .resv = XFS_AG_RESV_NONE, }; int error; ASSERT(xfs_has_rmapbt(sc->mp)); ASSERT(sc->ip != NULL); ASSERT(xfs_is_metadir_inode(sc->ip)); xreap_configure_agextent_limits(&rs); xfs_rmap_ino_bmbt_owner(&oinfo, sc->ip->i_ino, XFS_DATA_FORK); error = xfsb_bitmap_walk(bitmap, xreap_fsmeta_extent, &rs); if (error) return error; if (xreap_is_dirty(&rs)) { error = xrep_defer_finish(sc); if (error) return error; } return xrep_reset_metafile_resv(sc); } /* * Metadata files are not supposed to share blocks with anything else. * If blocks are shared, we remove the reverse mapping (thus reducing the * crosslink factor); if blocks are not shared, we also need to free them. * * This first step determines the longest subset of the passed-in imap * (starting at its beginning) that is either crosslinked or not crosslinked. * The blockcount will be adjust down as needed. */ STATIC int xreap_bmapi_select( struct xreap_state *rs, struct xfs_bmbt_irec *imap, bool *crosslinked) { struct xfs_owner_info oinfo; struct xfs_scrub *sc = rs->sc; struct xfs_btree_cur *cur; xfs_filblks_t len = 1; xfs_agblock_t bno; xfs_agblock_t agbno; xfs_agblock_t agbno_next; int error; agbno = XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock); agbno_next = agbno + imap->br_blockcount; cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, sc->sa.agf_bp, sc->sa.pag); xfs_rmap_ino_owner(&oinfo, rs->ip->i_ino, rs->whichfork, imap->br_startoff); error = xfs_rmap_has_other_keys(cur, agbno, 1, &oinfo, crosslinked); if (error) goto out_cur; bno = agbno + 1; while (bno < agbno_next) { bool also_crosslinked; oinfo.oi_offset++; error = xfs_rmap_has_other_keys(cur, bno, 1, &oinfo, &also_crosslinked); if (error) goto out_cur; if (also_crosslinked != *crosslinked) break; len++; bno++; } imap->br_blockcount = len; trace_xreap_bmapi_select(pag_group(sc->sa.pag), agbno, len, *crosslinked); out_cur: xfs_btree_del_cursor(cur, error); return error; } /* * Decide if this buffer can be joined to a transaction. This is true for most * buffers, but there are two cases that we want to catch: large remote xattr * value buffers are not logged and can overflow the buffer log item dirty * bitmap size; and oversized cached buffers if things have really gone * haywire. */ static inline bool xreap_buf_loggable( const struct xfs_buf *bp) { int i; for (i = 0; i < bp->b_map_count; i++) { int chunks; int map_size; chunks = DIV_ROUND_UP(BBTOB(bp->b_maps[i].bm_len), XFS_BLF_CHUNK); map_size = DIV_ROUND_UP(chunks, NBWORD); if (map_size > XFS_BLF_DATAMAP_SIZE) return false; } return true; } /* * Invalidate any buffers for this file mapping. The @imap blockcount may be * adjusted downward if we need to roll the transaction. */ STATIC int xreap_bmapi_binval( struct xreap_state *rs, struct xfs_bmbt_irec *imap) { struct xfs_scrub *sc = rs->sc; struct xfs_mount *mp = sc->mp; struct xfs_perag *pag = sc->sa.pag; int bmap_flags = xfs_bmapi_aflag(rs->whichfork); xfs_fileoff_t off; xfs_fileoff_t max_off; xfs_extlen_t scan_blocks; xfs_agblock_t bno; xfs_agblock_t agbno; xfs_agblock_t agbno_next; int error; /* * Avoid invalidating AG headers and post-EOFS blocks because we never * own those. */ agbno = bno = XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock); agbno_next = agbno + imap->br_blockcount; if (!xfs_verify_agbno(pag, agbno) || !xfs_verify_agbno(pag, agbno_next - 1)) return 0; /* * Buffers for file blocks can span multiple contiguous mappings. This * means that for each block in the mapping, there could exist an * xfs_buf indexed by that block with any length up to the maximum * buffer size (remote xattr values) or to the next hole in the fork. * To set up our binval scan, first we need to figure out the location * of the next hole. */ off = imap->br_startoff + imap->br_blockcount; max_off = off + xfs_attr3_max_rmt_blocks(mp); while (off < max_off) { struct xfs_bmbt_irec hmap; int nhmaps = 1; error = xfs_bmapi_read(rs->ip, off, max_off - off, &hmap, &nhmaps, bmap_flags); if (error) return error; if (nhmaps != 1 || hmap.br_startblock == DELAYSTARTBLOCK) { ASSERT(0); return -EFSCORRUPTED; } if (!xfs_bmap_is_real_extent(&hmap)) break; off = hmap.br_startoff + hmap.br_blockcount; } scan_blocks = off - imap->br_startoff; trace_xreap_bmapi_binval_scan(sc, imap, scan_blocks); /* * If there are incore buffers for these blocks, invalidate them. If * we can't (try)lock the buffer we assume it's owned by someone else * and leave it alone. The buffer cache cannot detect aliasing, so * employ nested loops to detect incore buffers of any plausible size. */ while (bno < agbno_next) { struct xrep_bufscan scan = { .daddr = xfs_agbno_to_daddr(pag, bno), .max_sectors = xrep_bufscan_max_sectors(mp, scan_blocks), .daddr_step = XFS_FSB_TO_BB(mp, 1), }; struct xfs_buf *bp; while ((bp = xrep_bufscan_advance(mp, &scan)) != NULL) { if (xreap_buf_loggable(bp)) { xfs_trans_bjoin(sc->tp, bp); xfs_trans_binval(sc->tp, bp); } else { xfs_buf_stale(bp); xfs_buf_relse(bp); } /* * Stop invalidating if we've hit the limit; we should * still have enough reservation left to free however * far we've gotten. */ if (!xreap_inc_binval(rs)) { imap->br_blockcount = agbno_next - bno; goto out; } } bno++; scan_blocks--; } out: trace_xreap_bmapi_binval(pag_group(sc->sa.pag), agbno, imap->br_blockcount); return 0; } /* * Dispose of as much of the beginning of this file fork mapping as possible. * The number of blocks disposed of is returned in @imap->br_blockcount. */ STATIC int xrep_reap_bmapi_iter( struct xreap_state *rs, struct xfs_bmbt_irec *imap, bool crosslinked) { struct xfs_scrub *sc = rs->sc; int error; if (crosslinked) { /* * If there are other rmappings, this block is cross linked and * must not be freed. Remove the reverse mapping, leave the * buffer cache in its possibly confused state, and move on. * We don't want to risk discarding valid data buffers from * anybody else who thinks they own the block, even though that * runs the risk of stale buffer warnings in the future. */ trace_xreap_dispose_unmap_extent(pag_group(sc->sa.pag), XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock), imap->br_blockcount); /* * t0: Schedule removal of the mapping from the fork. We use * deferred log intents in this function to control the exact * sequence of metadata updates. */ xfs_bmap_unmap_extent(sc->tp, rs->ip, rs->whichfork, imap); xfs_trans_mod_dquot_byino(sc->tp, rs->ip, XFS_TRANS_DQ_BCOUNT, -(int64_t)imap->br_blockcount); xfs_rmap_unmap_extent(sc->tp, rs->ip, rs->whichfork, imap); return 0; } /* * If the block is not crosslinked, we can invalidate all the incore * buffers for the extent, and then free the extent. This is a bit of * a mess since we don't detect discontiguous buffers that are indexed * by a block starting before the first block of the extent but overlap * anyway. */ trace_xreap_dispose_free_extent(pag_group(sc->sa.pag), XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock), imap->br_blockcount); /* * Invalidate as many buffers as we can, starting at the beginning of * this mapping. If this function sets blockcount to zero, the * transaction is full of logged buffer invalidations, so we need to * return early so that we can roll and retry. */ error = xreap_bmapi_binval(rs, imap); if (error || imap->br_blockcount == 0) return error; /* * t1: Schedule removal of the mapping from the fork. We use deferred * work in this function to control the exact sequence of metadata * updates. */ xfs_bmap_unmap_extent(sc->tp, rs->ip, rs->whichfork, imap); xfs_trans_mod_dquot_byino(sc->tp, rs->ip, XFS_TRANS_DQ_BCOUNT, -(int64_t)imap->br_blockcount); return xfs_free_extent_later(sc->tp, imap->br_startblock, imap->br_blockcount, NULL, XFS_AG_RESV_NONE, XFS_FREE_EXTENT_SKIP_DISCARD); } /* Compute the maximum mapcount of a file buffer. */ static unsigned int xreap_bmapi_binval_mapcount( struct xfs_scrub *sc) { /* directory blocks can span multiple fsblocks and be discontiguous */ if (sc->sm->sm_type == XFS_SCRUB_TYPE_DIR) return sc->mp->m_dir_geo->fsbcount; /* all other file xattr/symlink blocks must be contiguous */ return 1; } /* Compute the maximum block size of a file buffer. */ static unsigned int xreap_bmapi_binval_blocksize( struct xfs_scrub *sc) { switch (sc->sm->sm_type) { case XFS_SCRUB_TYPE_DIR: return sc->mp->m_dir_geo->blksize; case XFS_SCRUB_TYPE_XATTR: case XFS_SCRUB_TYPE_PARENT: /* * The xattr structure itself consists of single fsblocks, but * there could be remote xattr blocks to invalidate. */ return XFS_XATTR_SIZE_MAX; } /* everything else is a single block */ return sc->mp->m_sb.sb_blocksize; } /* * Compute the maximum number of buffer invalidations that we can do while * reaping a single extent from a file fork. */ STATIC void xreap_configure_bmapi_limits( struct xreap_state *rs) { struct xfs_scrub *sc = rs->sc; struct xfs_mount *mp = sc->mp; /* overhead of invalidating a buffer */ const unsigned int per_binval = xfs_buf_inval_log_space(xreap_bmapi_binval_mapcount(sc), xreap_bmapi_binval_blocksize(sc)); /* * In the worst case, relogging an intent item causes both an intent * item and a done item to be attached to a transaction for each extent * that we'd like to process. */ const unsigned int efi = xfs_efi_log_space(1) + xfs_efd_log_space(1); const unsigned int rui = xfs_rui_log_space(1) + xfs_rud_log_space(); const unsigned int bui = xfs_bui_log_space(1) + xfs_bud_log_space(); /* * t1: Unmapping crosslinked file data blocks: one bmap deletion, * possibly an EFI for underfilled bmbt blocks, and an rmap deletion. * * t2: Freeing freeing file data blocks: one bmap deletion, possibly an * EFI for underfilled bmbt blocks, and another EFI for the space * itself. */ const unsigned int t1 = (bui + efi) + rui; const unsigned int t2 = (bui + efi) + efi; const unsigned int per_intent = max(t1, t2); /* * For each transaction in a reap chain, we must be able to take one * step in the defer item chain, which should only consist of CUI, EFI, * or RUI items. */ const unsigned int f1 = xfs_calc_finish_efi_reservation(mp, 1); const unsigned int f2 = xfs_calc_finish_rui_reservation(mp, 1); const unsigned int f3 = xfs_calc_finish_bui_reservation(mp, 1); const unsigned int step_size = max3(f1, f2, f3); /* * Each call to xreap_ifork_extent starts with a clean transaction and * operates on a single mapping by creating a chain of log intent items * for that mapping. We need to leave enough reservation in the * transaction to log btree buffer and inode updates for each step in * the chain, and to relog the log intents. */ const unsigned int per_extent_res = per_intent + step_size; xreap_configure_limits(rs, per_extent_res, per_binval, 0, per_binval); trace_xreap_bmapi_limits(sc->tp, per_binval, rs->max_binval, step_size, per_intent, 1); } /* * Dispose of as much of this file extent as we can. Upon successful return, * the imap will reflect the mapping that was removed from the fork. */ STATIC int xreap_ifork_extent( struct xreap_state *rs, struct xfs_bmbt_irec *imap) { struct xfs_scrub *sc = rs->sc; xfs_agnumber_t agno; bool crosslinked; int error; ASSERT(sc->sa.pag == NULL); trace_xreap_ifork_extent(sc, rs->ip, rs->whichfork, imap); agno = XFS_FSB_TO_AGNO(sc->mp, imap->br_startblock); sc->sa.pag = xfs_perag_get(sc->mp, agno); if (!sc->sa.pag) return -EFSCORRUPTED; error = xfs_alloc_read_agf(sc->sa.pag, sc->tp, 0, &sc->sa.agf_bp); if (error) goto out_pag; /* * Decide the fate of the blocks at the beginning of the mapping, then * update the mapping to use it with the unmap calls. */ error = xreap_bmapi_select(rs, imap, &crosslinked); if (error) goto out_agf; error = xrep_reap_bmapi_iter(rs, imap, crosslinked); if (error) goto out_agf; out_agf: xfs_trans_brelse(sc->tp, sc->sa.agf_bp); sc->sa.agf_bp = NULL; out_pag: xfs_perag_put(sc->sa.pag); sc->sa.pag = NULL; return error; } /* * Dispose of each block mapped to the given fork of the given file. Callers * must hold ILOCK_EXCL, and ip can only be sc->ip or sc->tempip. The fork * must not have any delalloc reservations. */ int xrep_reap_ifork( struct xfs_scrub *sc, struct xfs_inode *ip, int whichfork) { struct xreap_state rs = { .sc = sc, .ip = ip, .whichfork = whichfork, }; xfs_fileoff_t off = 0; int bmap_flags = xfs_bmapi_aflag(whichfork); int error; ASSERT(xfs_has_rmapbt(sc->mp)); ASSERT(ip == sc->ip || ip == sc->tempip); ASSERT(whichfork == XFS_ATTR_FORK || !XFS_IS_REALTIME_INODE(ip)); xreap_configure_bmapi_limits(&rs); while (off < XFS_MAX_FILEOFF) { struct xfs_bmbt_irec imap; int nimaps = 1; /* Read the next extent, skip past holes and delalloc. */ error = xfs_bmapi_read(ip, off, XFS_MAX_FILEOFF - off, &imap, &nimaps, bmap_flags); if (error) return error; if (nimaps != 1 || imap.br_startblock == DELAYSTARTBLOCK) { ASSERT(0); return -EFSCORRUPTED; } /* * If this is a real space mapping, reap as much of it as we * can in a single transaction. */ if (xfs_bmap_is_real_extent(&imap)) { error = xreap_ifork_extent(&rs, &imap); if (error) return error; error = xfs_defer_finish(&sc->tp); if (error) return error; xreap_defer_finish_reset(&rs); } off = imap.br_startoff + imap.br_blockcount; } return 0; }