MFC r306424: MFV r306422:

7254 ztest failed assertion in ztest_dataset_dirobj_verify: dirobjs + 1 == usedobjs

dsl_dataset_space is looking at the ds_bp's fill count while
dmu_objset_write_ready() is concurrently modifying it. This fix adds an
rrwlock to protect the ds_bp.

Closes #180

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Steve Gonczi <steve.gonczi@delphix.com>
Author: Paul Dagnelie <pcd@delphix.com>

1 files changed, 29 insertions, 6 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c
index 5eecc23..aad0086 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dbuf.c
@@ -1489,10 +1489,18 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
 	 * objects may be dirtied in syncing context, but only if they
 	 * were already pre-dirtied in open context.
 	 */
+#ifdef DEBUG
+	if (dn->dn_objset->os_dsl_dataset != NULL) {
+		rrw_enter(&dn->dn_objset->os_dsl_dataset->ds_bp_rwlock,
+		    RW_READER, FTAG);
+	}
 	ASSERT(!dmu_tx_is_syncing(tx) ||
 	    BP_IS_HOLE(dn->dn_objset->os_rootbp) ||
 	    DMU_OBJECT_IS_SPECIAL(dn->dn_object) ||
 	    dn->dn_objset->os_dsl_dataset == NULL);
+	if (dn->dn_objset->os_dsl_dataset != NULL)
+		rrw_exit(&dn->dn_objset->os_dsl_dataset->ds_bp_rwlock, FTAG);
+#endif
 	/*
 	 * We make this assert for private objects as well, but after we
 	 * check if we're already dirty.  They are allowed to re-dirty
@@ -1517,12 +1525,21 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
 	 * Don't set dirtyctx to SYNC if we're just modifying this as we
 	 * initialize the objset.
 	 */
-	if (dn->dn_dirtyctx == DN_UNDIRTIED &&
-	    !BP_IS_HOLE(dn->dn_objset->os_rootbp)) {
-		dn->dn_dirtyctx =
-		    (dmu_tx_is_syncing(tx) ? DN_DIRTY_SYNC : DN_DIRTY_OPEN);
-		ASSERT(dn->dn_dirtyctx_firstset == NULL);
-		dn->dn_dirtyctx_firstset = kmem_alloc(1, KM_SLEEP);
+	if (dn->dn_dirtyctx == DN_UNDIRTIED) {
+		if (dn->dn_objset->os_dsl_dataset != NULL) {
+			rrw_enter(&dn->dn_objset->os_dsl_dataset->ds_bp_rwlock,
+			    RW_READER, FTAG);
+		}
+		if (!BP_IS_HOLE(dn->dn_objset->os_rootbp)) {
+			dn->dn_dirtyctx = (dmu_tx_is_syncing(tx) ?
+			    DN_DIRTY_SYNC : DN_DIRTY_OPEN);
+			ASSERT(dn->dn_dirtyctx_firstset == NULL);
+			dn->dn_dirtyctx_firstset = kmem_alloc(1, KM_SLEEP);
+		}
+		if (dn->dn_objset->os_dsl_dataset != NULL) {
+			rrw_exit(&dn->dn_objset->os_dsl_dataset->ds_bp_rwlock,
+			    FTAG);
+		}
 	}
 	mutex_exit(&dn->dn_mtx);
 
@@ -1567,8 +1584,14 @@ dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
 	 * this assertion only if we're not already dirty.
 	 */
 	os = dn->dn_objset;
+#ifdef DEBUG
+	if (dn->dn_objset->os_dsl_dataset != NULL)
+		rrw_enter(&os->os_dsl_dataset->ds_bp_rwlock, RW_READER, FTAG);
 	ASSERT(!dmu_tx_is_syncing(tx) || DMU_OBJECT_IS_SPECIAL(dn->dn_object) ||
 	    os->os_dsl_dataset == NULL || BP_IS_HOLE(os->os_rootbp));
+	if (dn->dn_objset->os_dsl_dataset != NULL)
+		rrw_exit(&os->os_dsl_dataset->ds_bp_rwlock, FTAG);
+#endif
 	ASSERT(db->db.db_size != 0);
 
 	dprintf_dbuf(db, "size=%llx\n", (u_longlong_t)db->db.db_size);