From cd32e5db8bb4411533dc21cfc12a5af5f3b56701 Mon Sep 17 00:00:00 2001 From: Tom Caputi Date: Mon, 18 Jun 2018 17:10:54 -0400 Subject: [PATCH] Add ASSERT to debug encryption key mapping issues This patch simply adds an ASSERT that confirms that the last decrypting reference on a dataset waits until the dataset is no longer dirty. This should help to debug issues where the ZIO layer cannot find encryption keys after a dataset has been disowned. Reviewed-by: Brian Behlendorf Signed-off-by: Tom Caputi Closes #7637 --- include/sys/dmu.h | 1 + module/zfs/dbuf.c | 14 ++++++++++++++ module/zfs/dsl_dataset.c | 9 +++++++++ 3 files changed, 24 insertions(+) diff --git a/include/sys/dmu.h b/include/sys/dmu.h index e5950be93b..44c026286d 100644 --- a/include/sys/dmu.h +++ b/include/sys/dmu.h @@ -557,6 +557,7 @@ boolean_t dmu_buf_try_add_ref(dmu_buf_t *, objset_t *os, uint64_t object, void dmu_buf_rele(dmu_buf_t *db, void *tag); uint64_t dmu_buf_refcount(dmu_buf_t *db); +uint64_t dmu_buf_user_refcount(dmu_buf_t *db); /* * dmu_buf_hold_array holds the DMU buffers which contain all bytes in a diff --git a/module/zfs/dbuf.c b/module/zfs/dbuf.c index 2411c8d4f3..e3738db525 100644 --- a/module/zfs/dbuf.c +++ b/module/zfs/dbuf.c @@ -3306,6 +3306,20 @@ dbuf_refcount(dmu_buf_impl_t *db) return (refcount_count(&db->db_holds)); } +uint64_t +dmu_buf_user_refcount(dmu_buf_t *db_fake) +{ + uint64_t holds; + dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake; + + mutex_enter(&db->db_mtx); + ASSERT3U(refcount_count(&db->db_holds), >=, db->db_dirtycnt); + holds = refcount_count(&db->db_holds) - db->db_dirtycnt; + mutex_exit(&db->db_mtx); + + return (holds); +} + void * dmu_buf_replace_user(dmu_buf_t *db_fake, dmu_buf_user_t *old_user, dmu_buf_user_t *new_user) diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c index 7a4721e17f..9db6d1e0be 100644 --- a/module/zfs/dsl_dataset.c +++ b/module/zfs/dsl_dataset.c @@ -791,6 +791,15 @@ dsl_dataset_rele_flags(dsl_dataset_t *ds, ds_hold_flags_t flags, void *tag) (flags & DS_HOLD_FLAG_DECRYPT)) { (void) spa_keystore_remove_mapping(ds->ds_dir->dd_pool->dp_spa, ds->ds_object, ds); + + /* + * Encrypted datasets require that users only release their + * decrypting reference after the dirty data has actually + * been written out. This ensures that the mapping exists + * when it is needed to write out dirty data. + */ + ASSERT(dmu_buf_user_refcount(ds->ds_dbuf) != 0 || + !dsl_dataset_is_dirty(ds)); } dmu_buf_rele(ds->ds_dbuf, tag);