Illumos #3578, #3579

3578 transferring the freed map to the defer map should be constant time
3579 ztest trips assertion in metaslab_weight()
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Richard Elling <richard.elling@dey-sys.com>
Approved by: Dan McDonald <danmcd@nexenta.com>

References:
  https://www.illumos.org/issues/3578
  https://www.illumos.org/issues/3579
  illumos/illumos-gate@9eb57f7f3fbb970d4b9b89dcd5ecf543fe2414d5

Ported-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index 7837822e405e6f71f6934c730e9a1d30cc152ad2..e92af491b6f70896d62574b5db71472c41efbb53 100644 (file)
--- a/module/zfs/metaslab.c
+++ b/module/zfs/metaslab.c
@@ -830,6 +830,16 @@ metaslab_weight(metaslab_t *msp)
 
        ASSERT(MUTEX_HELD(&msp->ms_lock));
 
+       /*
+        * This vdev is in the process of being removed so there is nothing
+        * for us to do here.
+        */
+       if (vd->vdev_removing) {
+               ASSERT0(smo->smo_alloc);
+               ASSERT0(vd->vdev_ms_shift);
+               return (0);
+       }
+
        /*
         * The baseline weight is the metaslab's free space.
         */
@@ -1212,8 +1222,8 @@ metaslab_sync_done(metaslab_t *msp, uint64_t txg)
        space_map_obj_t *smo = &msp->ms_smo;
        space_map_obj_t *smosync = &msp->ms_smo_syncing;
        space_map_t *sm = msp->ms_map;
-       space_map_t *freed_map = msp->ms_freemap[TXG_CLEAN(txg) & TXG_MASK];
-       space_map_t *defer_map = msp->ms_defermap[txg % TXG_DEFER_SIZE];
+       space_map_t **freed_map = &msp->ms_freemap[TXG_CLEAN(txg) & TXG_MASK];
+       space_map_t **defer_map = &msp->ms_defermap[txg % TXG_DEFER_SIZE];
        metaslab_group_t *mg = msp->ms_group;
        vdev_t *vd = mg->mg_vd;
        int64_t alloc_delta, defer_delta;
@@ -1227,8 +1237,8 @@ metaslab_sync_done(metaslab_t *msp, uint64_t txg)
         * If this metaslab is just becoming available, initialize its
         * allocmaps, freemaps, and defermap and add its capacity to the vdev.
         */
-       if (freed_map == NULL) {
-               ASSERT(defer_map == NULL);
+       if (*freed_map == NULL) {
+               ASSERT(*defer_map == NULL);
                for (t = 0; t < TXG_SIZE; t++) {
                        msp->ms_allocmap[t] = kmem_zalloc(sizeof (space_map_t),
                            KM_PUSHPAGE);
@@ -1247,14 +1257,14 @@ metaslab_sync_done(metaslab_t *msp, uint64_t txg)
                            sm->sm_size, sm->sm_shift, sm->sm_lock);
                }
 
-               freed_map = msp->ms_freemap[TXG_CLEAN(txg) & TXG_MASK];
-               defer_map = msp->ms_defermap[txg % TXG_DEFER_SIZE];
+               freed_map = &msp->ms_freemap[TXG_CLEAN(txg) & TXG_MASK];
+               defer_map = &msp->ms_defermap[txg % TXG_DEFER_SIZE];
 
                vdev_space_update(vd, 0, 0, sm->sm_size);
        }
 
        alloc_delta = smosync->smo_alloc - smo->smo_alloc;
-       defer_delta = freed_map->sm_space - defer_map->sm_space;
+       defer_delta = (*freed_map)->sm_space - (*defer_map)->sm_space;
 
        vdev_space_update(vd, alloc_delta + defer_delta, defer_delta, 0);
 
@@ -1264,12 +1274,18 @@ metaslab_sync_done(metaslab_t *msp, uint64_t txg)
        /*
         * If there's a space_map_load() in progress, wait for it to complete
         * so that we have a consistent view of the in-core space map.
-        * Then, add defer_map (oldest deferred frees) to this map and
-        * transfer freed_map (this txg's frees) to defer_map.
         */
        space_map_load_wait(sm);
-       space_map_vacate(defer_map, sm->sm_loaded ? space_map_free : NULL, sm);
-       space_map_vacate(freed_map, space_map_add, defer_map);
+
+       /*
+        * Move the frees from the defer_map to this map (if it's loaded).
+        * Swap the freed_map and the defer_map -- this is safe to do
+        * because we've just emptied out the defer_map.
+        */
+       space_map_vacate(*defer_map, sm->sm_loaded ? space_map_free : NULL, sm);
+       ASSERT0((*defer_map)->sm_space);
+       ASSERT0(avl_numnodes(&(*defer_map)->sm_root));
+       space_map_swap(freed_map, defer_map);
 
        *smo = *smosync;