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, 18 insertions, 15 deletions

diff --git a/module/zfs/zap.c b/module/zfs/zap.c
index 9e4f05049..d0d438fe3 100644
--- a/module/zfs/zap.c
+++ b/module/zfs/zap.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  */
 
@@ -605,7 +605,8 @@ zap_deref_leaf(zap_t *zap, uint64_t h, dmu_tx_t *tx, krw_t lt, zap_leaf_t **lp)
 }
 
 static int
-zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx, zap_leaf_t **lp)
+zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l,
+    void *tag, dmu_tx_t *tx, zap_leaf_t **lp)
 {
 	zap_t *zap = zn->zn_zap;
 	uint64_t hash = zn->zn_hash;
@@ -627,9 +628,9 @@ zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx, zap_leaf_t **lp)
 		uint64_t object = zap->zap_object;
 
 		zap_put_leaf(l);
-		zap_unlockdir(zap);
+		zap_unlockdir(zap, tag);
 		err = zap_lockdir(os, object, tx, RW_WRITER,
-		    FALSE, FALSE, &zn->zn_zap);
+		    FALSE, FALSE, tag, &zn->zn_zap);
 		zap = zn->zn_zap;
 		if (err)
 			return (err);
@@ -692,7 +693,8 @@ zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx, zap_leaf_t **lp)
 }
 
 static void
-zap_put_leaf_maybe_grow_ptrtbl(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx)
+zap_put_leaf_maybe_grow_ptrtbl(zap_name_t *zn, zap_leaf_t *l,
+    void *tag, dmu_tx_t *tx)
 {
 	zap_t *zap = zn->zn_zap;
 	int shift = zap_f_phys(zap)->zap_ptrtbl.zt_shift;
@@ -712,9 +714,9 @@ zap_put_leaf_maybe_grow_ptrtbl(zap_name_t *zn, zap_leaf_t *l, dmu_tx_t *tx)
 			objset_t *os = zap->zap_objset;
 			uint64_t zapobj = zap->zap_object;
 
-			zap_unlockdir(zap);
+			zap_unlockdir(zap, tag);
 			err = zap_lockdir(os, zapobj, tx,
-			    RW_WRITER, FALSE, FALSE, &zn->zn_zap);
+			    RW_WRITER, FALSE, FALSE, tag, &zn->zn_zap);
 			zap = zn->zn_zap;
 			if (err)
 				return;
@@ -804,7 +806,7 @@ fzap_lookup(zap_name_t *zn,
 int
 fzap_add_cd(zap_name_t *zn,
     uint64_t integer_size, uint64_t num_integers,
-    const void *val, uint32_t cd, dmu_tx_t *tx)
+    const void *val, uint32_t cd, void *tag, dmu_tx_t *tx)
 {
 	zap_leaf_t *l;
 	int err;
@@ -833,7 +835,7 @@ retry:
 	if (err == 0) {
 		zap_increment_num_entries(zap, 1, tx);
 	} else if (err == EAGAIN) {
-		err = zap_expand_leaf(zn, l, tx, &l);
+		err = zap_expand_leaf(zn, l, tag, tx, &l);
 		zap = zn->zn_zap;	/* zap_expand_leaf() may change zap */
 		if (err == 0)
 			goto retry;
@@ -841,26 +843,27 @@ retry:
 
 out:
 	if (zap != NULL)
-		zap_put_leaf_maybe_grow_ptrtbl(zn, l, tx);
+		zap_put_leaf_maybe_grow_ptrtbl(zn, l, tag, tx);
 	return (err);
 }
 
 int
 fzap_add(zap_name_t *zn,
     uint64_t integer_size, uint64_t num_integers,
-    const void *val, dmu_tx_t *tx)
+    const void *val, void *tag, dmu_tx_t *tx)
 {
 	int err = fzap_check(zn, integer_size, num_integers);
 	if (err != 0)
 		return (err);
 
 	return (fzap_add_cd(zn, integer_size, num_integers,
-	    val, ZAP_NEED_CD, tx));
+	    val, ZAP_NEED_CD, tag, tx));
 }
 
 int
 fzap_update(zap_name_t *zn,
-    int integer_size, uint64_t num_integers, const void *val, dmu_tx_t *tx)
+    int integer_size, uint64_t num_integers, const void *val,
+    void *tag, dmu_tx_t *tx)
 {
 	zap_leaf_t *l;
 	int err, create;
@@ -890,14 +893,14 @@ retry:
 	}
 
 	if (err == EAGAIN) {
-		err = zap_expand_leaf(zn, l, tx, &l);
+		err = zap_expand_leaf(zn, l, tag, tx, &l);
 		zap = zn->zn_zap;	/* zap_expand_leaf() may change zap */
 		if (err == 0)
 			goto retry;
 	}
 
 	if (zap != NULL)
-		zap_put_leaf_maybe_grow_ptrtbl(zn, l, tx);
+		zap_put_leaf_maybe_grow_ptrtbl(zn, l, tag, tx);
 	return (err);
 }