OpenZFS 7003 - zap_lockdir() should tag hold

zap_lockdir() / zap_unlockdir() should take a "void *tag" argument which
tags the hold on the zap. This will help diagnose programming errors
which misuse the hold on the ZAP.

Sponsored by: Intel Corp.

Signed-off-by: Matthew Ahrens <[email protected]>
Signed-off-by: Pavel Zakharov <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>

OpenZFS-issue: https://www.illumos.org/issues/7003
OpenZFS-commit: https://github.com/openzfs/openzfs/pull/108
Closes #4972

1 files changed, 120 insertions, 86 deletions

diff --git a/module/zfs/zap_micro.c b/module/zfs/zap_micro.c
index f3153cc18..de646287e 100644
--- a/module/zfs/zap_micro.c
+++ b/module/zfs/zap_micro.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  */
 
@@ -42,7 +42,8 @@
 
 extern inline mzap_phys_t *zap_m_phys(zap_t *zap);
 
-static int mzap_upgrade(zap_t **zapp, dmu_tx_t *tx, zap_flags_t flags);
+static int mzap_upgrade(zap_t **zapp,
+    void *tag, dmu_tx_t *tx, zap_flags_t flags);
 
 uint64_t
 zap_getflags(zap_t *zap)
@@ -456,21 +457,19 @@ handle_winner:
 	return (winner);
 }
 
-int
-zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
+static int
+zap_lockdir_impl(dmu_buf_t *db, void *tag, dmu_tx_t *tx,
     krw_t lti, boolean_t fatreader, boolean_t adding, zap_t **zapp)
 {
 	dmu_object_info_t doi;
 	zap_t *zap;
-	dmu_buf_t *db;
 	krw_t lt;
-	int err;
 
-	*zapp = NULL;
+	objset_t *os = dmu_buf_get_objset(db);
+	uint64_t obj = db->db_object;
 
-	err = dmu_buf_hold(os, obj, 0, NULL, &db, DMU_READ_NO_PREFETCH);
-	if (err)
-		return (err);
+	ASSERT0(db->db_offset);
+	*zapp = NULL;
 
 	dmu_object_info_from_db(db, &doi);
 	if (DMU_OT_BYTESWAP(doi.doi_type) != DMU_BSWAP_ZAP)
@@ -484,7 +483,6 @@ zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
 			 * mzap_open() didn't like what it saw on-disk.
 			 * Check for corruption!
 			 */
-			dmu_buf_rele(db, NULL);
 			return (SET_ERROR(EIO));
 		}
 	}
@@ -520,13 +518,16 @@ zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
 	    zap->zap_m.zap_num_entries == zap->zap_m.zap_num_chunks) {
 		uint64_t newsz = db->db_size + SPA_MINBLOCKSIZE;
 		if (newsz > MZAP_MAX_BLKSZ) {
+			int err;
 			dprintf("upgrading obj %llu: num_entries=%u\n",
 			    obj, zap->zap_m.zap_num_entries);
 			*zapp = zap;
-			return (mzap_upgrade(zapp, tx, 0));
+			err = mzap_upgrade(zapp, tag, tx, 0);
+			if (err != 0)
+				rw_exit(&zap->zap_rwlock);
+			return (err);
 		}
-		err = dmu_object_set_blocksize(os, obj, newsz, 0, tx);
-		ASSERT0(err);
+		VERIFY0(dmu_object_set_blocksize(os, obj, newsz, 0, tx));
 		zap->zap_m.zap_num_chunks =
 		    db->db_size / MZAP_ENT_LEN - 1;
 	}
@@ -535,15 +536,31 @@ zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
 	return (0);
 }
 
+int
+zap_lockdir(objset_t *os, uint64_t obj, dmu_tx_t *tx,
+    krw_t lti, boolean_t fatreader, boolean_t adding, void *tag, zap_t **zapp)
+{
+	dmu_buf_t *db;
+	int err;
+
+	err = dmu_buf_hold(os, obj, 0, tag, &db, DMU_READ_NO_PREFETCH);
+	if (err != 0)
+		return (err);
+	err = zap_lockdir_impl(db, tag, tx, lti, fatreader, adding, zapp);
+	if (err != 0)
+		dmu_buf_rele(db, tag);
+	return (err);
+}
+
 void
-zap_unlockdir(zap_t *zap)
+zap_unlockdir(zap_t *zap, void *tag)
 {
 	rw_exit(&zap->zap_rwlock);
-	dmu_buf_rele(zap->zap_dbuf, NULL);
+	dmu_buf_rele(zap->zap_dbuf, tag);
 }
 
 static int
-mzap_upgrade(zap_t **zapp, dmu_tx_t *tx, zap_flags_t flags)
+mzap_upgrade(zap_t **zapp, void *tag, dmu_tx_t *tx, zap_flags_t flags)
 {
 	mzap_phys_t *mzp;
 	int i, sz, nchunks;
@@ -581,7 +598,8 @@ mzap_upgrade(zap_t **zapp, dmu_tx_t *tx, zap_flags_t flags)
 		dprintf("adding %s=%llu\n",
 		    mze->mze_name, mze->mze_value);
 		zn = zap_name_alloc(zap, mze->mze_name, MT_EXACT);
-		err = fzap_add_cd(zn, 8, 1, &mze->mze_value, mze->mze_cd, tx);
+		err = fzap_add_cd(zn, 8, 1, &mze->mze_value, mze->mze_cd,
+		    tag, tx);
 		zap = zn->zn_zap;	/* fzap_add_cd() may change zap */
 		zap_name_free(zn);
 		if (err)
@@ -620,9 +638,9 @@ mzap_create_impl(objset_t *os, uint64_t obj, int normflags, zap_flags_t flags,
 		zap_t *zap;
 		/* Only fat zap supports flags; upgrade immediately. */
 		VERIFY(0 == zap_lockdir(os, obj, tx, RW_WRITER,
-		    B_FALSE, B_FALSE, &zap));
-		VERIFY3U(0, ==, mzap_upgrade(&zap, tx, flags));
-		zap_unlockdir(zap);
+		    B_FALSE, B_FALSE, FTAG, &zap));
+		VERIFY3U(0, ==, mzap_upgrade(&zap, FTAG, tx, flags));
+		zap_unlockdir(zap, FTAG);
 	}
 }
 
@@ -762,7 +780,7 @@ zap_count(objset_t *os, uint64_t zapobj, uint64_t *count)
 	zap_t *zap;
 	int err;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	if (!zap->zap_ismicro) {
@@ -770,7 +788,7 @@ zap_count(objset_t *os, uint64_t zapobj, uint64_t *count)
 	} else {
 		*count = zap->zap_m.zap_num_entries;
 	}
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -827,25 +845,19 @@ zap_lookup(objset_t *os, uint64_t zapobj, const char *name,
 	    num_integers, buf, MT_EXACT, NULL, 0, NULL));
 }
 
-int
-zap_lookup_norm(objset_t *os, uint64_t zapobj, const char *name,
+static int
+zap_lookup_impl(zap_t *zap, const char *name,
     uint64_t integer_size, uint64_t num_integers, void *buf,
     matchtype_t mt, char *realname, int rn_len,
     boolean_t *ncp)
 {
-	zap_t *zap;
-	int err;
+	int err = 0;
 	mzap_ent_t *mze;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
-	if (err)
-		return (err);
 	zn = zap_name_alloc(zap, name, mt);
-	if (zn == NULL) {
-		zap_unlockdir(zap);
+	if (zn == NULL)
 		return (SET_ERROR(ENOTSUP));
-	}
 
 	if (!zap->zap_ismicro) {
 		err = fzap_lookup(zn, integer_size, num_integers, buf,
@@ -872,7 +884,24 @@ zap_lookup_norm(objset_t *os, uint64_t zapobj, const char *name,
 		}
 	}
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	return (err);
+}
+
+int
+zap_lookup_norm(objset_t *os, uint64_t zapobj, const char *name,
+    uint64_t integer_size, uint64_t num_integers, void *buf,
+    matchtype_t mt, char *realname, int rn_len,
+    boolean_t *ncp)
+{
+	zap_t *zap;
+	int err;
+
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
+	if (err != 0)
+		return (err);
+	err = zap_lookup_impl(zap, name, integer_size,
+	    num_integers, buf, mt, realname, rn_len, ncp);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -883,18 +912,18 @@ zap_prefetch(objset_t *os, uint64_t zapobj, const char *name)
 	int err;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc(zap, name, MT_EXACT);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 
 	fzap_prefetch(zn);
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -906,18 +935,18 @@ zap_prefetch_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 	int err;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 
 	fzap_prefetch(zn);
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -929,19 +958,19 @@ zap_lookup_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 	int err;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 
 	err = fzap_lookup(zn, integer_size, num_integers, buf,
 	    NULL, 0, NULL);
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -964,12 +993,12 @@ zap_length(objset_t *os, uint64_t zapobj, const char *name,
 	mzap_ent_t *mze;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc(zap, name, MT_EXACT);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 	if (!zap->zap_ismicro) {
@@ -986,7 +1015,7 @@ zap_length(objset_t *os, uint64_t zapobj, const char *name,
 		}
 	}
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -998,17 +1027,17 @@ zap_length_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 	int err;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 	err = fzap_length(zn, integer_size, num_integers);
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -1068,22 +1097,24 @@ zap_add(objset_t *os, uint64_t zapobj, const char *key,
 	const uint64_t *intval = val;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, &zap);
+	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc(zap, key, MT_EXACT);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 	if (!zap->zap_ismicro) {
-		err = fzap_add(zn, integer_size, num_integers, val, tx);
+		err = fzap_add(zn, integer_size, num_integers, val, FTAG, tx);
 		zap = zn->zn_zap;	/* fzap_add() may change zap */
 	} else if (integer_size != 8 || num_integers != 1 ||
 	    strlen(key) >= MZAP_NAME_LEN) {
-		err = mzap_upgrade(&zn->zn_zap, tx, 0);
-		if (err == 0)
-			err = fzap_add(zn, integer_size, num_integers, val, tx);
+		err = mzap_upgrade(&zn->zn_zap, FTAG, tx, 0);
+		if (err == 0) {
+			err = fzap_add(zn, integer_size, num_integers, val,
+			    FTAG, tx);
+		}
 		zap = zn->zn_zap;	/* fzap_add() may change zap */
 	} else {
 		mze = mze_find(zn);
@@ -1096,7 +1127,7 @@ zap_add(objset_t *os, uint64_t zapobj, const char *key,
 	ASSERT(zap == zn->zn_zap);
 	zap_name_free(zn);
 	if (zap != NULL)	/* may be NULL if fzap_add() failed */
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -1109,19 +1140,19 @@ zap_add_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 	int err;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, &zap);
+	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
-	err = fzap_add(zn, integer_size, num_integers, val, tx);
+	err = fzap_add(zn, integer_size, num_integers, val, FTAG, tx);
 	zap = zn->zn_zap;	/* fzap_add() may change zap */
 	zap_name_free(zn);
 	if (zap != NULL)	/* may be NULL if fzap_add() failed */
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -1146,25 +1177,27 @@ zap_update(objset_t *os, uint64_t zapobj, const char *name,
 		(void) zap_lookup(os, zapobj, name, 8, 1, &oldval);
 #endif
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, &zap);
+	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc(zap, name, MT_EXACT);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 	if (!zap->zap_ismicro) {
-		err = fzap_update(zn, integer_size, num_integers, val, tx);
+		err = fzap_update(zn, integer_size, num_integers, val,
+		    FTAG, tx);
 		zap = zn->zn_zap;	/* fzap_update() may change zap */
 	} else if (integer_size != 8 || num_integers != 1 ||
 	    strlen(name) >= MZAP_NAME_LEN) {
 		dprintf("upgrading obj %llu: intsz=%u numint=%llu name=%s\n",
 		    zapobj, integer_size, num_integers, name);
-		err = mzap_upgrade(&zn->zn_zap, tx, 0);
-		if (err == 0)
+		err = mzap_upgrade(&zn->zn_zap, FTAG, tx, 0);
+		if (err == 0) {
 			err = fzap_update(zn, integer_size, num_integers,
-			    val, tx);
+			    val, FTAG, tx);
+		}
 		zap = zn->zn_zap;	/* fzap_update() may change zap */
 	} else {
 		mze = mze_find(zn);
@@ -1178,7 +1211,7 @@ zap_update(objset_t *os, uint64_t zapobj, const char *name,
 	ASSERT(zap == zn->zn_zap);
 	zap_name_free(zn);
 	if (zap != NULL)	/* may be NULL if fzap_upgrade() failed */
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -1191,19 +1224,19 @@ zap_update_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 	zap_name_t *zn;
 	int err;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, &zap);
+	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, TRUE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
-	err = fzap_update(zn, integer_size, num_integers, val, tx);
+	err = fzap_update(zn, integer_size, num_integers, val, FTAG, tx);
 	zap = zn->zn_zap;	/* fzap_update() may change zap */
 	zap_name_free(zn);
 	if (zap != NULL)	/* may be NULL if fzap_upgrade() failed */
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -1222,12 +1255,12 @@ zap_remove_norm(objset_t *os, uint64_t zapobj, const char *name,
 	mzap_ent_t *mze;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc(zap, name, mt);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 	if (!zap->zap_ismicro) {
@@ -1244,7 +1277,7 @@ zap_remove_norm(objset_t *os, uint64_t zapobj, const char *name,
 		}
 	}
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -1256,17 +1289,17 @@ zap_remove_uint64(objset_t *os, uint64_t zapobj, const uint64_t *key,
 	int err;
 	zap_name_t *zn;
 
-	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, tx, RW_WRITER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 	zn = zap_name_alloc_uint64(zap, key, key_numints);
 	if (zn == NULL) {
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, FTAG);
 		return (SET_ERROR(ENOTSUP));
 	}
 	err = fzap_remove(zn, tx);
 	zap_name_free(zn);
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }
 
@@ -1298,7 +1331,7 @@ zap_cursor_fini(zap_cursor_t *zc)
 {
 	if (zc->zc_zap) {
 		rw_enter(&zc->zc_zap->zap_rwlock, RW_READER);
-		zap_unlockdir(zc->zc_zap);
+		zap_unlockdir(zc->zc_zap, NULL);
 		zc->zc_zap = NULL;
 	}
 	if (zc->zc_leaf) {
@@ -1345,7 +1378,7 @@ zap_cursor_retrieve(zap_cursor_t *zc, zap_attribute_t *za)
 	if (zc->zc_zap == NULL) {
 		int hb;
 		err = zap_lockdir(zc->zc_objset, zc->zc_zapobj, NULL,
-		    RW_READER, TRUE, FALSE, &zc->zc_zap);
+		    RW_READER, TRUE, FALSE, NULL, &zc->zc_zap);
 		if (err)
 			return (err);
 
@@ -1409,7 +1442,7 @@ zap_get_stats(objset_t *os, uint64_t zapobj, zap_stats_t *zs)
 	int err;
 	zap_t *zap;
 
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, FTAG, &zap);
 	if (err)
 		return (err);
 
@@ -1422,7 +1455,7 @@ zap_get_stats(objset_t *os, uint64_t zapobj, zap_stats_t *zs)
 	} else {
 		fzap_get_stats(zap, zs);
 	}
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (0);
 }
 
@@ -1441,7 +1474,7 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
 	 * 	- 2 blocks for possibly split leaves,
 	 * 	- 2 grown ptrtbl blocks
 	 *
-	 * This also accomodates the case where an add operation to a fairly
+	 * This also accommodates the case where an add operation to a fairly
 	 * large microzap results in a promotion to fatzap.
 	 */
 	if (name == NULL) {
@@ -1453,10 +1486,11 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
 	 * We lock the zap with adding == FALSE. Because, if we pass
 	 * the actual value of add, it could trigger a mzap_upgrade().
 	 * At present we are just evaluating the possibility of this operation
-	 * and hence we donot want to trigger an upgrade.
+	 * and hence we do not want to trigger an upgrade.
 	 */
-	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE, &zap);
-	if (err)
+	err = zap_lockdir(os, zapobj, NULL, RW_READER, TRUE, FALSE,
+	    FTAG, &zap);
+	if (err != 0)
 		return (err);
 
 	if (!zap->zap_ismicro) {
@@ -1497,7 +1531,7 @@ zap_count_write(objset_t *os, uint64_t zapobj, const char *name, int add,
 		}
 	}
 
-	zap_unlockdir(zap);
+	zap_unlockdir(zap, FTAG);
 	return (err);
 }