]> www.infradead.org Git - users/hch/xfsprogs.git/commitdiff
xfs_repair: rebuild the realtime rmap btree
authorDarrick J. Wong <djwong@kernel.org>
Fri, 15 Jul 2022 21:27:25 +0000 (14:27 -0700)
committerDarrick J. Wong <djwong@kernel.org>
Wed, 22 Nov 2023 23:03:39 +0000 (15:03 -0800)
Rebuild the realtime rmap btree file from the reverse mapping records we
gathered from walking the inodes.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
libxfs/libxfs_api_defs.h
repair/Makefile
repair/bulkload.c
repair/bulkload.h
repair/phase6.c
repair/rmap.c
repair/rmap.h
repair/rtrmap_repair.c [new file with mode: 0644]
repair/xfs_repair.c

index 161c3059dc3cf59b5c1e1cde949506dff03eacf2..2ea3eefeff6277bdb4aca5c861c48e4125db5f55 100644 (file)
 #define xfs_rmap_irec_offset_unpack    libxfs_rmap_irec_offset_unpack
 #define xfs_rmap_lookup_le             libxfs_rmap_lookup_le
 #define xfs_rmap_lookup_le_range       libxfs_rmap_lookup_le_range
+#define xfs_rmap_map_extent            libxfs_rmap_map_extent
 #define xfs_rmap_map_raw               libxfs_rmap_map_raw
 #define xfs_rmap_query_all             libxfs_rmap_query_all
 #define xfs_rmap_query_range           libxfs_rmap_query_range
 #define xfs_rtgroup_put                        libxfs_rtgroup_put
 #define xfs_rtgroup_update_secondary_sbs       libxfs_rtgroup_update_secondary_sbs
 #define xfs_rtgroup_update_super       libxfs_rtgroup_update_super
+#define xfs_rtrmapbt_calc_size         libxfs_rtrmapbt_calc_size
+#define xfs_rtrmapbt_commit_staged_btree       libxfs_rtrmapbt_commit_staged_btree
+#define xfs_rtrmapbt_create            libxfs_rtrmapbt_create
 #define xfs_rtrmapbt_create_path       libxfs_rtrmapbt_create_path
 #define xfs_rtrmapbt_droot_maxrecs     libxfs_rtrmapbt_droot_maxrecs
 #define xfs_rtrmapbt_maxlevels_ondisk  libxfs_rtrmapbt_maxlevels_ondisk
 #define xfs_rtrmapbt_maxrecs           libxfs_rtrmapbt_maxrecs
 #define xfs_rtrmapbt_mem_create                libxfs_rtrmapbt_mem_create
 #define xfs_rtrmapbt_mem_cursor                libxfs_rtrmapbt_mem_cursor
+#define xfs_rtrmapbt_stage_cursor      libxfs_rtrmapbt_stage_cursor
 
 #define xfs_sb_from_disk               libxfs_sb_from_disk
 #define xfs_sb_quota_from_disk         libxfs_sb_quota_from_disk
index 1f72c811056f0afb35bf162c539aa52056997330..5bec8154829d8c32c136ccbf8b0b90d0739c1b32 100644 (file)
@@ -75,6 +75,7 @@ CFILES = \
        rcbag.c \
        rmap.c \
        rt.c \
+       rtrmap_repair.c \
        sb.c \
        scan.c \
        slab.c \
index a3c0a2ae71e845eb6218f0e0057385ada7cab535..5eef29f6d16edd9c34d602fd2952a6a61c1dcd32 100644 (file)
@@ -364,3 +364,44 @@ bulkload_estimate_ag_slack(
        if (bload->node_slack < 0)
                bload->node_slack = 2;
 }
+
+/*
+ * 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) The FS has less than ~9% space free.
+ *
+ * Note that we actually use 3/32 for the comparison to avoid division.
+ */
+void
+bulkload_estimate_inode_slack(
+       struct xfs_mount        *mp,
+       struct xfs_btree_bload  *bload,
+       unsigned long long      free)
+{
+       /*
+        * The global values are set to -1 (i.e. take the bload defaults)
+        * unless someone has set them otherwise, so we just pull the values
+        * here.
+        */
+       bload->leaf_slack = bload_leaf_slack;
+       bload->node_slack = bload_node_slack;
+
+       /* No further changes if there's more than 3/32ths space left. */
+       if (free >= ((mp->m_sb.sb_dblocks * 3) >> 5))
+               return;
+
+       /*
+        * We're low on space; load the btrees as tightly as possible.  Leave
+        * a couple of open slots in each btree block so that we don't end up
+        * splitting the btrees like crazy right after mount.
+        */
+       if (bload->leaf_slack < 0)
+               bload->leaf_slack = 2;
+       if (bload->node_slack < 0)
+               bload->node_slack = 2;
+}
index a88aafaa678a3a629f9f5322b0669790ea3d2430..842121b15190e7eeff1ea4752f2f87f81c52af2b 100644 (file)
@@ -78,5 +78,7 @@ void bulkload_cancel(struct bulkload *bkl);
 int bulkload_commit(struct bulkload *bkl);
 void bulkload_estimate_ag_slack(struct repair_ctx *sc,
                struct xfs_btree_bload *bload, unsigned int free);
+void bulkload_estimate_inode_slack(struct xfs_mount *mp,
+               struct xfs_btree_bload *bload, unsigned long long free);
 
 #endif /* __XFS_REPAIR_BULKLOAD_H__ */
index 63a2768d9c62ccbf2a7da84cda26dc81342f61fe..4c387557c3134fdb366ee6437298c14dd803b18d 100644 (file)
@@ -19,6 +19,8 @@
 #include "progress.h"
 #include "versions.h"
 #include "repair/pptr.h"
+#include "slab.h"
+#include "rmap.h"
 
 static xfs_ino_t               orphanage_ino;
 
@@ -1072,6 +1074,136 @@ mk_rsumino(
        libxfs_irele(ip);
 }
 
+static void
+ensure_rtgroup_rmapbt(
+       struct xfs_rtgroup      *rtg,
+       xfs_filblks_t           est_fdblocks)
+{
+       struct xfs_imeta_update upd;
+       struct xfs_mount        *mp = rtg->rtg_mount;
+       struct xfs_imeta_path   *path;
+       struct xfs_inode        *ip;
+       xfs_ino_t               ino;
+       int                     error;
+
+       if (!xfs_has_rtrmapbt(mp))
+               return;
+
+       ino = rtgroup_rmap_ino(rtg);
+       if (no_modify) {
+               if (ino == NULLFSINO)
+                       do_warn(_("would reset rtgroup %u rmap btree\n"),
+                                       rtg->rtg_rgno);
+               return;
+       }
+
+       if (ino == NULLFSINO)
+               do_warn(_("resetting rtgroup %u rmap btree\n"),
+                               rtg->rtg_rgno);
+
+       error = -libxfs_rtrmapbt_create_path(mp, rtg->rtg_rgno, &path);
+       if (error)
+               do_error(
+ _("Couldn't create rtgroup %u rmap file path, err %d\n"),
+                               rtg->rtg_rgno, error);
+
+       error = ensure_imeta_dirpath(mp, path);
+       if (error)
+               do_error(
+ _("Couldn't create rtgroup %u metadata directory, error %d\n"),
+                               rtg->rtg_rgno, error);
+
+       if (ino != NULLFSINO) {
+               struct xfs_trans        *tp;
+
+               /*
+                * We're still hanging on to our old inode pointer, so grab it
+                * and reconnect it to the metadata directory tree.  If it
+                * can't be grabbed, create a new rtrmap file.
+                */
+               error = -libxfs_trans_alloc_empty(mp, &tp);
+               if (error)
+                       do_error(
+ _("Couldn't allocate transaction to iget rtgroup %u rmap inode 0x%llx, error %d\n"),
+                                       rtg->rtg_rgno, (unsigned long long)ino,
+                                       error);
+               error = -libxfs_imeta_iget(tp, ino, XFS_DIR3_FT_REG_FILE, &ip);
+               libxfs_trans_cancel(tp);
+               if (error) {
+                       do_warn(
+ _("Couldn't iget rtgroup %u rmap inode 0x%llx, error %d\n"),
+                                       rtg->rtg_rgno, (unsigned long long)ino,
+                                       error);
+                       goto zap;
+               }
+
+               /*
+                * Since we're reattaching this file to the metadata directory
+                * tree, try to remove all the parent pointers that might be
+                * attached.
+                */
+               try_erase_parent_ptrs(ip);
+
+               error = -libxfs_imeta_start_link(mp, path, ip, &upd);
+               if (error)
+                       do_error(
+ _("Couldn't grab resources to reconnect rtgroup %u rmapbt, error %d\n"),
+                                       rtg->rtg_rgno, error);
+
+               error = -libxfs_imeta_link(&upd);
+               if (error)
+                       do_error(
+ _("Failed to link rtgroup %u rmapbt inode 0x%llx, error %d\n"),
+                                       rtg->rtg_rgno,
+                                       (unsigned long long)ip->i_ino,
+                                       error);
+
+               /* Reset the link count to something sane. */
+               set_nlink(VFS_I(ip), 1);
+               ip->i_df.if_format = XFS_DINODE_FMT_RMAP;
+               libxfs_trans_log_inode(upd.tp, ip, XFS_ILOG_CORE);
+       } else {
+zap:
+               /*
+                * The rtrmap inode was bad or gone, so just make a new one
+                * and give our reference to the rtgroup structure.
+                */
+               error = -libxfs_imeta_start_create(mp, path, &upd);
+               if (error)
+                       do_error(
+ _("Couldn't grab resources to recreate rtgroup %u rmapbt, error %d\n"),
+                                       rtg->rtg_rgno, error);
+
+               error = -libxfs_rtrmapbt_create(&upd, &ip);
+               if (error)
+                       do_error(
+ _("Couldn't create rtgroup %u rmap inode, error %d\n"),
+                                       rtg->rtg_rgno, error);
+       }
+
+       /* Mark the inode in use. */
+       mark_ino_inuse(mp, ip->i_ino, S_IFREG, upd.dp->i_ino);
+       mark_ino_metadata(mp, ip->i_ino);
+
+       error = -libxfs_imeta_commit_update(&upd);
+       if (error)
+               do_error(
+ _("Couldn't commit new rtgroup %u rmap inode %llu, error %d\n"),
+                               rtg->rtg_rgno,
+                               (unsigned long long)ip->i_ino,
+                               error);
+
+       /* Copy our incore rmap data to the ondisk rmap inode. */
+       error = populate_rtgroup_rmapbt(rtg, ip, est_fdblocks);
+       if (error)
+               do_error(
+ _("rtgroup %u rmap btree could not be rebuilt, error %d\n"),
+                               rtg->rtg_rgno, error);
+
+       libxfs_imeta_free_path(path);
+       libxfs_imeta_irele(ip);
+}
+
 /* Initialize a root directory. */
 static int
 init_fs_root_dir(
@@ -3838,6 +3970,27 @@ traverse_ags(
        do_inode_prefetch(mp, ag_stride, traverse_function, false, true);
 }
 
+static void
+reset_rt_metadata_inodes(
+       struct xfs_mount        *mp)
+{
+       struct xfs_rtgroup      *rtg;
+       xfs_filblks_t           metadata_blocks = 0;
+       xfs_filblks_t           est_fdblocks = 0;
+       xfs_rgnumber_t          rgno;
+
+       /* Estimate how much free space will be left after building btrees */
+       for_each_rtgroup(mp, rgno, rtg) {
+               metadata_blocks += estimate_rtrmapbt_blocks(rtg);
+       }
+       if (mp->m_sb.sb_fdblocks > metadata_blocks)
+               est_fdblocks = mp->m_sb.sb_fdblocks - metadata_blocks;
+
+       for_each_rtgroup(mp, rgno, rtg) {
+               ensure_rtgroup_rmapbt(rtg, est_fdblocks);
+       }
+}
+
 void
 phase6(xfs_mount_t *mp)
 {
@@ -3903,6 +4056,8 @@ phase6(xfs_mount_t *mp)
                }
        }
 
+       reset_rt_metadata_inodes(mp);
+
        if (!no_modify)  {
                do_log(
 _("        - resetting contents of realtime bitmap and summary inodes\n"));
index 5ac7188f12e672761f788d71922cde4fc95a0008..1312a0dde3448b409790990d1cdba864d360a4f7 100644 (file)
@@ -2106,3 +2106,29 @@ rtgroup_rmap_ino(
 
        return ar->rg_rmap_ino;
 }
+
+/* Estimate the size of the ondisk rtrmapbt from the incore tree. */
+xfs_filblks_t
+estimate_rtrmapbt_blocks(
+       struct xfs_rtgroup      *rtg)
+{
+       struct xfs_mount        *mp = rtg->rtg_mount;
+       struct xfs_ag_rmap      *x;
+       unsigned long long      nr_recs;
+
+       if (!rmap_needs_work(mp) || !xfs_has_rtrmapbt(mp))
+               return 0;
+
+       x = &rg_rmaps[rtg->rtg_rgno];
+       if (!x->ar_xfbtree)
+               return 0;
+
+       /*
+        * Overestimate the amount of space needed by pretending that every
+        * byte in the incore tree is used to store rtrmapbt records.  This
+        * means we can use SEEK_DATA/HOLE on the xfile, which is faster than
+        * walking the entire btree.
+        */
+       nr_recs = xfbtree_bytes(x->ar_xfbtree) / sizeof(struct xfs_rmap_rec);
+       return libxfs_rtrmapbt_calc_size(mp, nr_recs);
+}
index dcd834ef242aa198edac3bd7e17d1fe1826dec3f..1f99606a4553a4a57f511cd384c9e01cbf391723 100644 (file)
@@ -67,5 +67,8 @@ int rmap_get_mem_rec(struct rmap_mem_cur *rmcur, struct xfs_rmap_irec *irec);
 
 bool is_rtrmap_inode(xfs_ino_t ino);
 xfs_ino_t rtgroup_rmap_ino(struct xfs_rtgroup *rtg);
+int populate_rtgroup_rmapbt(struct xfs_rtgroup *rtg, struct xfs_inode *ip,
+               xfs_filblks_t fdblocks);
+xfs_filblks_t estimate_rtrmapbt_blocks(struct xfs_rtgroup *rtg);
 
 #endif /* RMAP_H_ */
diff --git a/repair/rtrmap_repair.c b/repair/rtrmap_repair.c
new file mode 100644 (file)
index 0000000..d3e96a5
--- /dev/null
@@ -0,0 +1,261 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2019-2023 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#include <libxfs.h>
+#include "btree.h"
+#include "err_protos.h"
+#include "libxlog.h"
+#include "incore.h"
+#include "globals.h"
+#include "dinode.h"
+#include "slab.h"
+#include "rmap.h"
+#include "bulkload.h"
+
+/* Ported routines from fs/xfs/scrub/rtrmap_repair.c */
+
+/*
+ * Realtime Reverse Mapping (RTRMAPBT) Repair
+ * ==========================================
+ *
+ * Gather all the rmap records for the inode and fork we're fixing, reset the
+ * incore fork, then recreate the btree.
+ */
+struct xrep_rtrmap {
+       struct rmap_mem_cur     btree_cursor;
+
+       /* New fork. */
+       struct bulkload         new_fork_info;
+       struct xfs_btree_bload  rtrmap_bload;
+
+       struct repair_ctx       *sc;
+       struct xfs_rtgroup      *rtg;
+
+       /* Estimated free space after building all rt btrees */
+       xfs_filblks_t           est_fdblocks;
+};
+
+/* Retrieve rtrmapbt data for bulk load. */
+STATIC int
+xrep_rtrmap_get_records(
+       struct xfs_btree_cur    *cur,
+       unsigned int            idx,
+       struct xfs_btree_block  *block,
+       unsigned int            nr_wanted,
+       void                    *priv)
+{
+       struct xrep_rtrmap      *rr = priv;
+       union xfs_btree_rec     *block_rec;
+       unsigned int            loaded;
+       int                     ret;
+
+       for (loaded = 0; loaded < nr_wanted; loaded++, idx++) {
+               ret = rmap_get_mem_rec(&rr->btree_cursor, &cur->bc_rec.r);
+               if (ret < 0)
+                       return ret;
+               if (ret == 0)
+                       do_error(
+ _("ran out of records while rebuilding rt rmap btree\n"));
+
+               block_rec = libxfs_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_rtrmap_claim_block(
+       struct xfs_btree_cur    *cur,
+       union xfs_btree_ptr     *ptr,
+       void                    *priv)
+{
+       struct xrep_rtrmap      *rr = priv;
+
+       return bulkload_claim_block(cur, &rr->new_fork_info, ptr);
+}
+
+/* Figure out how much space we need to create the incore btree root block. */
+STATIC size_t
+xrep_rtrmap_iroot_size(
+       struct xfs_btree_cur    *cur,
+       unsigned int            level,
+       unsigned int            nr_this_level,
+       void                    *priv)
+{
+       return xfs_rtrmap_broot_space_calc(cur->bc_mp, level, nr_this_level);
+}
+
+/* Reserve new btree blocks and bulk load all the rtrmap records. */
+STATIC int
+xrep_rtrmap_btree_load(
+       struct xrep_rtrmap      *rr,
+       struct xfs_btree_cur    *rtrmap_cur)
+{
+       struct repair_ctx       *sc = rr->sc;
+       int                     error;
+
+       rr->rtrmap_bload.get_records = xrep_rtrmap_get_records;
+       rr->rtrmap_bload.claim_block = xrep_rtrmap_claim_block;
+       rr->rtrmap_bload.iroot_size = xrep_rtrmap_iroot_size;
+       bulkload_estimate_inode_slack(sc->mp, &rr->rtrmap_bload,
+                       rr->est_fdblocks);
+
+       /* Compute how many blocks we'll need. */
+       error = -libxfs_btree_bload_compute_geometry(rtrmap_cur,
+                       &rr->rtrmap_bload,
+                       rmap_record_count(sc->mp, true, rr->rtg->rtg_rgno));
+       if (error)
+               return error;
+
+       /*
+        * Guess how many blocks we're going to need to rebuild an entire rtrmap
+        * from the number of extents we found, and pump up our transaction to
+        * have sufficient block reservation.
+        */
+       error = -libxfs_trans_reserve_more(sc->tp, rr->rtrmap_bload.nr_blocks,
+                       0);
+       if (error)
+               return error;
+
+       /*
+        * Reserve the space we'll need for the new btree.  Drop the cursor
+        * while we do this because that can roll the transaction and cursors
+        * can't handle that.
+        */
+       error = bulkload_alloc_file_blocks(&rr->new_fork_info,
+                       rr->rtrmap_bload.nr_blocks);
+       if (error)
+               return error;
+
+       /* Add all observed rtrmap records. */
+       error = rmap_init_mem_cursor(rr->sc->mp, sc->tp, true,
+                       rr->rtg->rtg_rgno, &rr->btree_cursor);
+       if (error)
+               return error;
+       error = -libxfs_btree_bload(rtrmap_cur, &rr->rtrmap_bload, rr);
+       rmap_free_mem_cursor(sc->tp, &rr->btree_cursor, error);
+       return error;
+}
+
+/* Update the inode counters. */
+STATIC int
+xrep_rtrmap_reset_counters(
+       struct xrep_rtrmap      *rr)
+{
+       struct repair_ctx       *sc = rr->sc;
+
+       /*
+        * Update the inode block counts to reflect the btree we just
+        * generated.
+        */
+       sc->ip->i_nblocks = rr->new_fork_info.ifake.if_blocks;
+       libxfs_trans_log_inode(sc->tp, sc->ip, XFS_ILOG_CORE);
+
+       /* Quotas don't exist so we're done. */
+       return 0;
+}
+
+/*
+ * Use the collected rmap information to stage a new rt rmap 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_rtrmap_build_new_tree(
+       struct xrep_rtrmap      *rr)
+{
+       struct xfs_owner_info   oinfo;
+       struct xfs_btree_cur    *cur;
+       struct repair_ctx       *sc = rr->sc;
+       struct xbtree_ifakeroot *ifake = &rr->new_fork_info.ifake;
+       int                     error;
+
+       /*
+        * Prepare to construct the new fork by initializing the new btree
+        * structure and creating a fake ifork in the ifakeroot structure.
+        */
+       libxfs_rmap_ino_bmbt_owner(&oinfo, sc->ip->i_ino, XFS_DATA_FORK);
+       bulkload_init_inode(&rr->new_fork_info, sc, XFS_DATA_FORK, &oinfo);
+       cur = libxfs_rtrmapbt_stage_cursor(sc->mp, rr->rtg, sc->ip, ifake);
+
+       /*
+        * Figure out the size and format of the new fork, then fill it with
+        * all the rtrmap records we've found.  Join the inode to the
+        * transaction so that we can roll the transaction while holding the
+        * inode locked.
+        */
+       libxfs_trans_ijoin(sc->tp, sc->ip, 0);
+       ifake->if_fork->if_format = XFS_DINODE_FMT_RMAP;
+       error = xrep_rtrmap_btree_load(rr, cur);
+       if (error)
+               goto err_cur;
+
+       /*
+        * Install the new fork in the inode.  After this point the old mapping
+        * data are no longer accessible and the new tree is live.  We delete
+        * the cursor immediately after committing the staged root because the
+        * staged fork might be in extents format.
+        */
+       libxfs_rtrmapbt_commit_staged_btree(cur, sc->tp);
+       libxfs_btree_del_cursor(cur, 0);
+
+       /* Reset the inode counters now that we've changed the fork. */
+       error = xrep_rtrmap_reset_counters(rr);
+       if (error)
+               goto err_newbt;
+
+       /* Dispose of any unused blocks and the accounting infomation. */
+       error = bulkload_commit(&rr->new_fork_info);
+       if (error)
+               return error;
+
+       return -libxfs_trans_roll_inode(&sc->tp, sc->ip);
+err_cur:
+       if (cur)
+               libxfs_btree_del_cursor(cur, error);
+err_newbt:
+       bulkload_cancel(&rr->new_fork_info);
+       return error;
+}
+
+/* Store the realtime reverse-mappings in the rtrmapbt. */
+int
+populate_rtgroup_rmapbt(
+       struct xfs_rtgroup      *rtg,
+       struct xfs_inode        *ip,
+       xfs_filblks_t           est_fdblocks)
+{
+       struct repair_ctx       sc = {
+               .mp             = rtg->rtg_mount,
+               .ip             = ip,
+       };
+       struct xrep_rtrmap      rr = {
+               .sc             = &sc,
+               .rtg            = rtg,
+               .est_fdblocks   = est_fdblocks,
+       };
+       struct xfs_mount        *mp = rtg->rtg_mount;
+       int                     error;
+
+       if (!xfs_has_rtrmapbt(mp))
+               return 0;
+
+       error = -libxfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0,
+                       &sc.tp);
+       if (error)
+               return error;
+
+       error = xrep_rtrmap_build_new_tree(&rr);
+       if (error)
+               goto out_cancel;
+
+       return -libxfs_trans_commit(sc.tp);
+
+out_cancel:
+       libxfs_trans_cancel(sc.tp);
+       return error;
+}
index efe0babe568daee484150abf7309f3c9baccfa1b..587dbc3471d0d336d404b8ea222565b5ef3db2fa 100644 (file)
@@ -1428,13 +1428,17 @@ main(int argc, char **argv)
        rcbagbt_destroy_cur_cache();
 
        /*
-        * Done with the block usage maps, toss them...
+        * Done with the block usage maps, toss them.  Realtime metadata aren't
+        * rebuilt until phase 6, so we have to keep them around.
         */
-       rmaps_free(mp);
+       if (mp->m_sb.sb_rblocks == 0)
+               rmaps_free(mp);
        free_bmaps(mp);
 
        if (!bad_ino_btree)  {
                phase6(mp);
+               if (mp->m_sb.sb_rblocks != 0)
+                       rmaps_free(mp);
                phase_end(mp, 6);
 
                phase7(mp, phase2_threads);