Use cached feature info in spa_add_feature_stats()
Avoid issuing I/O to the pool when retrieving feature flags information. Trying to read the ZAPs from disk means that zpool clear would hang if the pool is suspended and recovery would require a reboot. To keep the feature stats resident in memory, we hang a cached nvlist off of the spa. It is built up from disk the first time spa_add_feature_stats() is called, and refreshed thereafter using the cached feature reference counts. spa_add_feature_stats() gets called at pool import time so we can be sure the cached nvlist will be available if the pool is later suspended. Signed-off-by: Ned Bass <bass6@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #3082
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@ -236,6 +236,7 @@ struct spa {
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uint64_t spa_feat_for_read_obj; /* required to read from pool */
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uint64_t spa_feat_desc_obj; /* Feature descriptions */
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uint64_t spa_feat_enabled_txg_obj; /* Feature enabled txg */
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nvlist_t *spa_feat_stats; /* Cache of enabled features */
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/* cache feature refcounts */
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uint64_t spa_feat_refcount_cache[SPA_FEATURES];
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taskqid_t spa_deadman_tqid; /* Task id */
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@ -3202,15 +3202,11 @@ spa_add_l2cache(spa_t *spa, nvlist_t *config)
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}
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static void
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spa_add_feature_stats(spa_t *spa, nvlist_t *config)
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spa_feature_stats_from_disk(spa_t *spa, nvlist_t *features)
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{
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nvlist_t *features;
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zap_cursor_t zc;
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zap_attribute_t za;
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ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));
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VERIFY(nvlist_alloc(&features, NV_UNIQUE_NAME, KM_SLEEP) == 0);
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if (spa->spa_feat_for_read_obj != 0) {
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for (zap_cursor_init(&zc, spa->spa_meta_objset,
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spa->spa_feat_for_read_obj);
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@ -3218,7 +3214,7 @@ spa_add_feature_stats(spa_t *spa, nvlist_t *config)
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zap_cursor_advance(&zc)) {
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ASSERT(za.za_integer_length == sizeof (uint64_t) &&
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za.za_num_integers == 1);
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VERIFY3U(0, ==, nvlist_add_uint64(features, za.za_name,
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VERIFY0(nvlist_add_uint64(features, za.za_name,
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za.za_first_integer));
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}
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zap_cursor_fini(&zc);
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@ -3231,15 +3227,57 @@ spa_add_feature_stats(spa_t *spa, nvlist_t *config)
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zap_cursor_advance(&zc)) {
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ASSERT(za.za_integer_length == sizeof (uint64_t) &&
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za.za_num_integers == 1);
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VERIFY3U(0, ==, nvlist_add_uint64(features, za.za_name,
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VERIFY0(nvlist_add_uint64(features, za.za_name,
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za.za_first_integer));
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}
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zap_cursor_fini(&zc);
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}
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}
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VERIFY(nvlist_add_nvlist(config, ZPOOL_CONFIG_FEATURE_STATS,
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features) == 0);
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nvlist_free(features);
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static void
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spa_feature_stats_from_cache(spa_t *spa, nvlist_t *features)
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{
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int i;
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for (i = 0; i < SPA_FEATURES; i++) {
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zfeature_info_t feature = spa_feature_table[i];
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uint64_t refcount;
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if (feature_get_refcount(spa, &feature, &refcount) != 0)
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continue;
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VERIFY0(nvlist_add_uint64(features, feature.fi_guid, refcount));
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}
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}
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/*
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* Store a list of pool features and their reference counts in the
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* config.
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*
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* The first time this is called on a spa, allocate a new nvlist, fetch
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* the pool features and reference counts from disk, then save the list
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* in the spa. In subsequent calls on the same spa use the saved nvlist
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* and refresh its values from the cached reference counts. This
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* ensures we don't block here on I/O on a suspended pool so 'zpool
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* clear' can resume the pool.
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*/
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static void
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spa_add_feature_stats(spa_t *spa, nvlist_t *config)
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{
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nvlist_t *features = spa->spa_feat_stats;
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ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));
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if (features != NULL) {
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spa_feature_stats_from_cache(spa, features);
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} else {
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VERIFY0(nvlist_alloc(&features, NV_UNIQUE_NAME, KM_SLEEP));
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spa->spa_feat_stats = features;
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spa_feature_stats_from_disk(spa, features);
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}
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VERIFY0(nvlist_add_nvlist(config, ZPOOL_CONFIG_FEATURE_STATS,
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features));
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}
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int
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@ -643,6 +643,7 @@ spa_remove(spa_t *spa)
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nvlist_free(spa->spa_label_features);
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nvlist_free(spa->spa_load_info);
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nvlist_free(spa->spa_feat_stats);
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spa_config_set(spa, NULL);
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refcount_destroy(&spa->spa_refcount);
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@ -228,7 +228,7 @@ spa_features_check(spa_t *spa, boolean_t for_write,
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*
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* Note: well-designed features will not need to use this; they should
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* use spa_feature_is_enabled() and spa_feature_is_active() instead.
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* However, this is non-static for zdb and zhack.
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* However, this is non-static for zdb, zhack, and spa_add_feature_stats().
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*/
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int
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feature_get_refcount(spa_t *spa, zfeature_info_t *feature, uint64_t *res)
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