diff options
| -rw-r--r-- | module/zfs/zio.c | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/module/zfs/zio.c b/module/zfs/zio.c index 1af360c0bb7c..aeea58bedfe4 100644 --- a/module/zfs/zio.c +++ b/module/zfs/zio.c @@ -4574,8 +4574,29 @@ zio_vdev_io_start(zio_t *zio) ASSERT0(zio->io_child_error[ZIO_CHILD_VDEV]); if (vd == NULL) { - if (!(zio->io_flags & ZIO_FLAG_CONFIG_WRITER)) - spa_config_enter(spa, SCL_ZIO, zio, RW_READER); + if (!(zio->io_flags & ZIO_FLAG_CONFIG_WRITER)) { + /* + * A deadlock workaround. The ddt_prune_unique_entries() + * -> prune_candidates_sync() code path takes the + * SCL_ZIO reader lock and may request it again here. + * If there is another thread who wants the SCL_ZIO + * writer lock, then scl_write_wanted will be set. + * Thus, the spa_config_enter_priority() is used to + * ignore pending writer requests. + * + * The locking should be revised to remove the need + * for this workaround. If that's not workable then + * it should only be applied to the zios involved in + * the pruning process. This impacts the read/write + * I/O balance while pruning. + */ + if (spa->spa_active_ddt_prune) + spa_config_enter_priority(spa, SCL_ZIO, zio, + RW_READER); + else + spa_config_enter(spa, SCL_ZIO, zio, + RW_READER); + } /* * The mirror_ops handle multiple DVAs in a single BP. |