Illumos #3104: eliminate empty bpobjs

[zfs.git] / module / zfs / bpobj.c

diff --git a/module/zfs/bpobj.c b/module/zfs/bpobj.c
index 022921c..d5f8d40 100644 (file)
--- a/module/zfs/bpobj.c
+++ b/module/zfs/bpobj.c
@@ -20,13 +20,61 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011 by Delphix. All rights reserved.
+ * Copyright (c) 2012 by Delphix. All rights reserved.
  */
 
 #include <sys/bpobj.h>
 #include <sys/zfs_context.h>
 #include <sys/refcount.h>
 #include <sys/dsl_pool.h>
+#include <sys/zfeature.h>
+#include <sys/zap.h>
+
+/*
+ * Return an empty bpobj, preferably the empty dummy one (dp_empty_bpobj).
+ */
+uint64_t
+bpobj_alloc_empty(objset_t *os, int blocksize, dmu_tx_t *tx)
+{
+       zfeature_info_t *empty_bpobj_feat =
+           &spa_feature_table[SPA_FEATURE_EMPTY_BPOBJ];
+       spa_t *spa = dmu_objset_spa(os);
+       dsl_pool_t *dp = dmu_objset_pool(os);
+
+       if (spa_feature_is_enabled(spa, empty_bpobj_feat)) {
+               if (!spa_feature_is_active(spa, empty_bpobj_feat)) {
+                       ASSERT3U(dp->dp_empty_bpobj, ==, 0);
+                       dp->dp_empty_bpobj =
+                           bpobj_alloc(os, SPA_MAXBLOCKSIZE, tx);
+                       VERIFY(zap_add(os,
+                           DMU_POOL_DIRECTORY_OBJECT,
+                           DMU_POOL_EMPTY_BPOBJ, sizeof (uint64_t), 1,
+                           &dp->dp_empty_bpobj, tx) == 0);
+               }
+               spa_feature_incr(spa, empty_bpobj_feat, tx);
+               ASSERT(dp->dp_empty_bpobj != 0);
+               return (dp->dp_empty_bpobj);
+       } else {
+               return (bpobj_alloc(os, blocksize, tx));
+       }
+}
+
+void
+bpobj_decr_empty(objset_t *os, dmu_tx_t *tx)
+{
+       zfeature_info_t *empty_bpobj_feat =
+           &spa_feature_table[SPA_FEATURE_EMPTY_BPOBJ];
+       dsl_pool_t *dp = dmu_objset_pool(os);
+
+       spa_feature_decr(dmu_objset_spa(os), empty_bpobj_feat, tx);
+       if (!spa_feature_is_active(dmu_objset_spa(os), empty_bpobj_feat)) {
+               VERIFY3U(0, ==, zap_remove(dp->dp_meta_objset,
+                   DMU_POOL_DIRECTORY_OBJECT,
+                   DMU_POOL_EMPTY_BPOBJ, tx));
+               VERIFY3U(0, ==, dmu_object_free(os, dp->dp_empty_bpobj, tx));
+               dp->dp_empty_bpobj = 0;
+       }
+}
 
 uint64_t
 bpobj_alloc(objset_t *os, int blocksize, dmu_tx_t *tx)
@@ -53,6 +101,7 @@ bpobj_free(objset_t *os, uint64_t obj, dmu_tx_t *tx)
        int epb;
        dmu_buf_t *dbuf = NULL;
 
+       ASSERT(obj != dmu_objset_pool(os)->dp_empty_bpobj);
        VERIFY3U(0, ==, bpobj_open(&bpo, os, obj));
 
        mutex_enter(&bpo.bpo_lock);
@@ -320,6 +369,12 @@ bpobj_enqueue_subobj(bpobj_t *bpo, uint64_t subobj, dmu_tx_t *tx)
 
        ASSERT(bpo->bpo_havesubobj);
        ASSERT(bpo->bpo_havecomp);
+       ASSERT(bpo->bpo_object != dmu_objset_pool(bpo->bpo_os)->dp_empty_bpobj);
+
+       if (subobj == dmu_objset_pool(bpo->bpo_os)->dp_empty_bpobj) {
+               bpobj_decr_empty(bpo->bpo_os, tx);
+               return;
+       }
 
        VERIFY3U(0, ==, bpobj_open(&subbpo, bpo->bpo_os, subobj));
        VERIFY3U(0, ==, bpobj_space(&subbpo, &used, &comp, &uncomp));
@@ -388,6 +443,7 @@ bpobj_enqueue(bpobj_t *bpo, const blkptr_t *bp, dmu_tx_t *tx)
        blkptr_t *bparray;
 
        ASSERT(!BP_IS_HOLE(bp));
+       ASSERT(bpo->bpo_object != dmu_objset_pool(bpo->bpo_os)->dp_empty_bpobj);
 
        /* We never need the fill count. */
        stored_bp.blk_fill = 0;