diff options
Diffstat (limited to 'module')
| -rw-r--r-- | module/zfs/dmu_object.c | 8 | ||||
| -rw-r--r-- | module/zfs/dmu_traverse.c | 49 |
2 files changed, 43 insertions, 14 deletions
diff --git a/module/zfs/dmu_object.c b/module/zfs/dmu_object.c index 127a6757f..5faecafc7 100644 --- a/module/zfs/dmu_object.c +++ b/module/zfs/dmu_object.c @@ -20,7 +20,7 @@ */ /* * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. - * Copyright (c) 2013, 2014 by Delphix. All rights reserved. + * Copyright (c) 2013, 2015 by Delphix. All rights reserved. * Copyright 2014 HybridCluster. All rights reserved. */ @@ -50,6 +50,12 @@ dmu_object_alloc(objset_t *os, dmu_object_type_t ot, int blocksize, * reasonably sparse (at most 1/4 full). Look from the * beginning once, but after that keep looking from here. * If we can't find one, just keep going from here. + * + * Note that dmu_traverse depends on the behavior that we use + * multiple blocks of the dnode object before going back to + * reuse objects. Any change to this algorithm should preserve + * that property or find another solution to the issues + * described in traverse_visitbp. */ if (P2PHASE(object, L2_dnode_count) == 0) { uint64_t offset = restarted ? object << DNODE_SHIFT : 0; diff --git a/module/zfs/dmu_traverse.c b/module/zfs/dmu_traverse.c index 07164161b..bba9efe14 100644 --- a/module/zfs/dmu_traverse.c +++ b/module/zfs/dmu_traverse.c @@ -20,7 +20,7 @@ */ /* * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. - * Copyright (c) 2012, 2014 by Delphix. All rights reserved. + * Copyright (c) 2012, 2016 by Delphix. All rights reserved. */ #include <sys/zfs_context.h> @@ -61,6 +61,7 @@ typedef struct traverse_data { uint64_t td_hole_birth_enabled_txg; blkptr_cb_t *td_func; void *td_arg; + boolean_t td_realloc_possible; } traverse_data_t; static int traverse_dnode(traverse_data_t *td, const dnode_phys_t *dnp, @@ -228,18 +229,30 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp, if (bp->blk_birth == 0) { /* - * Since this block has a birth time of 0 it must be a - * hole created before the SPA_FEATURE_HOLE_BIRTH - * feature was enabled. If SPA_FEATURE_HOLE_BIRTH - * was enabled before the min_txg for this traveral we - * know the hole must have been created before the - * min_txg for this traveral, so we can skip it. If - * SPA_FEATURE_HOLE_BIRTH was enabled after the min_txg - * for this traveral we cannot tell if the hole was - * created before or after the min_txg for this - * traversal, so we cannot skip it. + * Since this block has a birth time of 0 it must be one of + * two things: a hole created before the + * SPA_FEATURE_HOLE_BIRTH feature was enabled, or a hole + * which has always been a hole in an object. + * + * If a file is written sparsely, then the unwritten parts of + * the file were "always holes" -- that is, they have been + * holes since this object was allocated. However, we (and + * our callers) can not necessarily tell when an object was + * allocated. Therefore, if it's possible that this object + * was freed and then its object number reused, we need to + * visit all the holes with birth==0. + * + * If it isn't possible that the object number was reused, + * then if SPA_FEATURE_HOLE_BIRTH was enabled before we wrote + * all the blocks we will visit as part of this traversal, + * then this hole must have always existed, so we can skip + * it. We visit blocks born after (exclusive) td_min_txg. + * + * Note that the meta-dnode cannot be reallocated. */ - if (td->td_hole_birth_enabled_txg < td->td_min_txg) + if ((!td->td_realloc_possible || + zb->zb_object == DMU_META_DNODE_OBJECT) && + td->td_hole_birth_enabled_txg <= td->td_min_txg) return (0); } else if (bp->blk_birth <= td->td_min_txg) { return (0); @@ -347,6 +360,15 @@ traverse_visitbp(traverse_data_t *td, const dnode_phys_t *dnp, prefetch_dnode_metadata(td, mdnp, zb->zb_objset, DMU_META_DNODE_OBJECT); + /* + * See the block comment above for the goal of this variable. + * If the maxblkid of the meta-dnode is 0, then we know that + * we've never had more than DNODES_PER_BLOCK objects in the + * dataset, which means we can't have reused any object ids. + */ + if (osp->os_meta_dnode.dn_maxblkid == 0) + td->td_realloc_possible = B_FALSE; + if (arc_buf_size(buf) >= sizeof (objset_phys_t)) { prefetch_dnode_metadata(td, gdnp, zb->zb_objset, DMU_GROUPUSED_OBJECT); @@ -554,12 +576,13 @@ traverse_impl(spa_t *spa, dsl_dataset_t *ds, uint64_t objset, blkptr_t *rootbp, td->td_pfd = pd; td->td_flags = flags; td->td_paused = B_FALSE; + td->td_realloc_possible = (txg_start == 0 ? B_FALSE : B_TRUE); if (spa_feature_is_active(spa, SPA_FEATURE_HOLE_BIRTH)) { VERIFY(spa_feature_enabled_txg(spa, SPA_FEATURE_HOLE_BIRTH, &td->td_hole_birth_enabled_txg)); } else { - td->td_hole_birth_enabled_txg = 0; + td->td_hole_birth_enabled_txg = UINT64_MAX; } pd->pd_flags = flags; |