From 12c6510e2ff17cf94cae08ba7b6d2355760dfd1d Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 29 May 2018 22:18:10 -0700 Subject: xfs: add helpers to dispose of old btree blocks after a repair Now that we've plumbed in the ability to construct a list of dead btree blocks following a repair, add more helpers to dispose of them. This is done by examining the rmapbt -- if the btree was the only owner we can free the block, otherwise it's crosslinked and we can only remove the rmapbt record. Signed-off-by: Darrick J. Wong Reviewed-by: Dave Chinner --- fs/xfs/scrub/repair.c | 251 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 251 insertions(+) (limited to 'fs/xfs/scrub/repair.c') diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c index fca8e3c7887d..7daf0120d1bf 100644 --- a/fs/xfs/scrub/repair.c +++ b/fs/xfs/scrub/repair.c @@ -585,3 +585,254 @@ out: } #undef LEFT_ALIGNED #undef RIGHT_ALIGNED + +/* + * Disposal of Blocks from Old per-AG Btrees + * + * 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 (exlist) 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 exlist. In theory the extents + * remaining in exlist 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 @exlist, + * 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 for the entire rebuild + * operation so that nothing else can sneak in and change the AG state while + * we're not looking. We also assume that the caller already invalidated any + * buffers associated with @exlist. + */ + +/* + * Invalidate buffers for per-AG btree blocks we're dumping. This function + * is not intended for use with file data repairs; we have bunmapi for that. + */ +int +xfs_repair_invalidate_blocks( + struct xfs_scrub_context *sc, + struct xfs_repair_extent_list *exlist) +{ + struct xfs_repair_extent *rex; + struct xfs_repair_extent *n; + struct xfs_buf *bp; + xfs_fsblock_t fsbno; + xfs_agblock_t i; + + /* + * For each block in each extent, see if there's an incore buffer for + * exactly that block; if so, invalidate it. The buffer cache only + * lets us look for one buffer at a time, so we have to look one block + * at a time. Avoid invalidating AG headers and post-EOFS blocks + * because we never own those; and if we can't TRYLOCK the buffer we + * assume it's owned by someone else. + */ + for_each_xfs_repair_extent_safe(rex, n, exlist) { + for (fsbno = rex->fsbno, i = rex->len; i > 0; fsbno++, i--) { + /* Skip AG headers and post-EOFS blocks */ + if (!xfs_verify_fsbno(sc->mp, fsbno)) + continue; + bp = xfs_buf_incore(sc->mp->m_ddev_targp, + XFS_FSB_TO_DADDR(sc->mp, fsbno), + XFS_FSB_TO_BB(sc->mp, 1), XBF_TRYLOCK); + if (bp) { + xfs_trans_bjoin(sc->tp, bp); + xfs_trans_binval(sc->tp, bp); + } + } + } + + return 0; +} + +/* Ensure the freelist is the correct size. */ +int +xfs_repair_fix_freelist( + struct xfs_scrub_context *sc, + bool can_shrink) +{ + struct xfs_alloc_arg args = {0}; + + args.mp = sc->mp; + args.tp = sc->tp; + args.agno = sc->sa.agno; + args.alignment = 1; + args.pag = sc->sa.pag; + + return xfs_alloc_fix_freelist(&args, + can_shrink ? 0 : XFS_ALLOC_FLAG_NOSHRINK); +} + +/* + * Put a block back on the AGFL. + */ +STATIC int +xfs_repair_put_freelist( + struct xfs_scrub_context *sc, + xfs_agblock_t agbno) +{ + struct xfs_owner_info oinfo; + int error; + + /* Make sure there's space on the freelist. */ + error = xfs_repair_fix_freelist(sc, true); + 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. + */ + xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_AG); + error = xfs_rmap_alloc(sc->tp, sc->sa.agf_bp, sc->sa.agno, agbno, 1, + &oinfo); + if (error) + return error; + + /* Put the block on the AGFL. */ + error = xfs_alloc_put_freelist(sc->tp, sc->sa.agf_bp, sc->sa.agfl_bp, + agbno, 0); + if (error) + return error; + xfs_extent_busy_insert(sc->tp, sc->sa.agno, agbno, 1, + XFS_EXTENT_BUSY_SKIP_DISCARD); + + return 0; +} + +/* Dispose of a single metadata block. */ +STATIC int +xfs_repair_dispose_btree_block( + struct xfs_scrub_context *sc, + xfs_fsblock_t fsbno, + struct xfs_owner_info *oinfo, + enum xfs_ag_resv_type resv) +{ + struct xfs_btree_cur *cur; + struct xfs_buf *agf_bp = NULL; + xfs_agnumber_t agno; + xfs_agblock_t agbno; + bool has_other_rmap; + int error; + + agno = XFS_FSB_TO_AGNO(sc->mp, fsbno); + agbno = XFS_FSB_TO_AGBNO(sc->mp, fsbno); + + /* + * If we are repairing per-inode metadata, we need to read in the AGF + * buffer. Otherwise, we're repairing a per-AG structure, so reuse + * the AGF buffer that the setup functions already grabbed. + */ + if (sc->ip) { + error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf_bp); + if (error) + return error; + if (!agf_bp) + return -ENOMEM; + } else { + agf_bp = sc->sa.agf_bp; + } + cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, agf_bp, agno); + + /* Can we find any other rmappings? */ + error = xfs_rmap_has_other_keys(cur, agbno, 1, oinfo, &has_other_rmap); + if (error) + goto out_cur; + xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR); + + /* + * 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 (has_other_rmap) + error = xfs_rmap_free(sc->tp, agf_bp, agno, agbno, 1, oinfo); + else if (resv == XFS_AG_RESV_AGFL) + error = xfs_repair_put_freelist(sc, agbno); + else + error = xfs_free_extent(sc->tp, fsbno, 1, oinfo, resv); + if (agf_bp != sc->sa.agf_bp) + xfs_trans_brelse(sc->tp, agf_bp); + if (error) + return error; + + if (sc->ip) + return xfs_trans_roll_inode(&sc->tp, sc->ip); + return xfs_repair_roll_ag_trans(sc); + +out_cur: + xfs_btree_del_cursor(cur, XFS_BTREE_ERROR); + if (agf_bp != sc->sa.agf_bp) + xfs_trans_brelse(sc->tp, agf_bp); + return error; +} + +/* Dispose of btree blocks from an old per-AG btree. */ +int +xfs_repair_reap_btree_extents( + struct xfs_scrub_context *sc, + struct xfs_repair_extent_list *exlist, + struct xfs_owner_info *oinfo, + enum xfs_ag_resv_type type) +{ + struct xfs_repair_extent *rex; + struct xfs_repair_extent *n; + int error = 0; + + ASSERT(xfs_sb_version_hasrmapbt(&sc->mp->m_sb)); + + /* Dispose of every block from the old btree. */ + for_each_xfs_repair_extent_safe(rex, n, exlist) { + ASSERT(sc->ip != NULL || + XFS_FSB_TO_AGNO(sc->mp, rex->fsbno) == sc->sa.agno); + + trace_xfs_repair_dispose_btree_extent(sc->mp, + XFS_FSB_TO_AGNO(sc->mp, rex->fsbno), + XFS_FSB_TO_AGBNO(sc->mp, rex->fsbno), rex->len); + + for (; rex->len > 0; rex->len--, rex->fsbno++) { + error = xfs_repair_dispose_btree_block(sc, rex->fsbno, + oinfo, type); + if (error) + goto out; + } + list_del(&rex->list); + kmem_free(rex); + } + +out: + xfs_repair_cancel_btree_extents(sc, exlist); + return error; +} -- cgit v1.2.3