diff options
| -rw-r--r-- | module/zfs/dsl_scan.c | 54 |
1 files changed, 50 insertions, 4 deletions
diff --git a/module/zfs/dsl_scan.c b/module/zfs/dsl_scan.c index 2b95561a9..166d0c1eb 100644 --- a/module/zfs/dsl_scan.c +++ b/module/zfs/dsl_scan.c @@ -872,7 +872,16 @@ dsl_scan_ds_destroyed(dsl_dataset_t *ds, dmu_tx_t *tx) if (scn->scn_phys.scn_bookmark.zb_objset == ds->ds_object) { if (ds->ds_is_snapshot) { - /* Note, scn_cur_{min,max}_txg stays the same. */ + /* + * Note: + * - scn_cur_{min,max}_txg stays the same. + * - Setting the flag is not really necessary if + * scn_cur_max_txg == scn_max_txg, because there + * is nothing after this snapshot that we care + * about. However, we set it anyway and then + * ignore it when we retraverse it in + * dsl_scan_visitds(). + */ scn->scn_phys.scn_bookmark.zb_objset = dsl_dataset_phys(ds)->ds_next_snap_obj; zfs_dbgmsg("destroying ds %llu; currently traversing; " @@ -912,9 +921,6 @@ dsl_scan_ds_destroyed(dsl_dataset_t *ds, dmu_tx_t *tx) zfs_dbgmsg("destroying ds %llu; in queue; removing", (u_longlong_t)ds->ds_object); } - } else { - zfs_dbgmsg("destroying ds %llu; ignoring", - (u_longlong_t)ds->ds_object); } /* @@ -1068,6 +1074,46 @@ dsl_scan_visitds(dsl_scan_t *scn, uint64_t dsobj, dmu_tx_t *tx) VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds)); + if (scn->scn_phys.scn_cur_min_txg >= + scn->scn_phys.scn_max_txg) { + /* + * This can happen if this snapshot was created after the + * scan started, and we already completed a previous snapshot + * that was created after the scan started. This snapshot + * only references blocks with: + * + * birth < our ds_creation_txg + * cur_min_txg is no less than ds_creation_txg. + * We have already visited these blocks. + * or + * birth > scn_max_txg + * The scan requested not to visit these blocks. + * + * Subsequent snapshots (and clones) can reference our + * blocks, or blocks with even higher birth times. + * Therefore we do not need to visit them either, + * so we do not add them to the work queue. + * + * Note that checking for cur_min_txg >= cur_max_txg + * is not sufficient, because in that case we may need to + * visit subsequent snapshots. This happens when min_txg > 0, + * which raises cur_min_txg. In this case we will visit + * this dataset but skip all of its blocks, because the + * rootbp's birth time is < cur_min_txg. Then we will + * add the next snapshots/clones to the work queue. + */ + char *dsname = kmem_alloc(MAXNAMELEN, KM_SLEEP); + dsl_dataset_name(ds, dsname); + zfs_dbgmsg("scanning dataset %llu (%s) is unnecessary because " + "cur_min_txg (%llu) >= max_txg (%llu)", + dsobj, dsname, + scn->scn_phys.scn_cur_min_txg, + scn->scn_phys.scn_max_txg); + kmem_free(dsname, MAXNAMELEN); + + goto out; + } + if (dmu_objset_from_ds(ds, &os)) goto out; |