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Add ASSERT to debug encryption key mapping issues

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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 <behlendorf1@llnl.gov>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #7637
This commit is contained in:
Tom Caputi 2018-06-18 17:10:54 -04:00 committed by Brian Behlendorf
parent 517d247192
commit cd32e5db8b
3 changed files with 24 additions and 0 deletions
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1
include/sys/dmu.h
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@ -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

14
module/zfs/dbuf.c
View File

@ -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)

9
module/zfs/dsl_dataset.c
View File

@ -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);