From 417104bdd3c7ce07ec58674dd078f9891c3bc780 Mon Sep 17 00:00:00 2001 From: Ned Bass Date: Thu, 26 Feb 2015 12:24:11 -0800 Subject: [PATCH] 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 Signed-off-by: Brian Behlendorf Closes #3082 --- include/sys/spa_impl.h | 1 + module/zfs/spa.c | 58 ++++++++++++++++++++++++++++++++++-------- module/zfs/spa_misc.c | 1 + module/zfs/zfeature.c | 2 +- 4 files changed, 51 insertions(+), 11 deletions(-) diff --git a/include/sys/spa_impl.h b/include/sys/spa_impl.h index 1cb535b9f..72e04e8cf 100644 --- a/include/sys/spa_impl.h +++ b/include/sys/spa_impl.h @@ -236,6 +236,7 @@ struct spa { uint64_t spa_feat_for_read_obj; /* required to read from pool */ uint64_t spa_feat_desc_obj; /* Feature descriptions */ uint64_t spa_feat_enabled_txg_obj; /* Feature enabled txg */ + nvlist_t *spa_feat_stats; /* Cache of enabled features */ /* cache feature refcounts */ uint64_t spa_feat_refcount_cache[SPA_FEATURES]; taskqid_t spa_deadman_tqid; /* Task id */ diff --git a/module/zfs/spa.c b/module/zfs/spa.c index 81cef1952..8bee15094 100644 --- a/module/zfs/spa.c +++ b/module/zfs/spa.c @@ -3202,15 +3202,11 @@ spa_add_l2cache(spa_t *spa, nvlist_t *config) } static void -spa_add_feature_stats(spa_t *spa, nvlist_t *config) +spa_feature_stats_from_disk(spa_t *spa, nvlist_t *features) { - nvlist_t *features; zap_cursor_t zc; zap_attribute_t za; - ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER)); - VERIFY(nvlist_alloc(&features, NV_UNIQUE_NAME, KM_SLEEP) == 0); - if (spa->spa_feat_for_read_obj != 0) { for (zap_cursor_init(&zc, spa->spa_meta_objset, spa->spa_feat_for_read_obj); @@ -3218,7 +3214,7 @@ spa_add_feature_stats(spa_t *spa, nvlist_t *config) zap_cursor_advance(&zc)) { ASSERT(za.za_integer_length == sizeof (uint64_t) && za.za_num_integers == 1); - VERIFY3U(0, ==, nvlist_add_uint64(features, za.za_name, + VERIFY0(nvlist_add_uint64(features, za.za_name, za.za_first_integer)); } zap_cursor_fini(&zc); @@ -3231,15 +3227,57 @@ spa_add_feature_stats(spa_t *spa, nvlist_t *config) zap_cursor_advance(&zc)) { ASSERT(za.za_integer_length == sizeof (uint64_t) && za.za_num_integers == 1); - VERIFY3U(0, ==, nvlist_add_uint64(features, za.za_name, + VERIFY0(nvlist_add_uint64(features, za.za_name, za.za_first_integer)); } zap_cursor_fini(&zc); } +} - VERIFY(nvlist_add_nvlist(config, ZPOOL_CONFIG_FEATURE_STATS, - features) == 0); - nvlist_free(features); +static void +spa_feature_stats_from_cache(spa_t *spa, nvlist_t *features) +{ + int i; + + for (i = 0; i < SPA_FEATURES; i++) { + zfeature_info_t feature = spa_feature_table[i]; + uint64_t refcount; + + if (feature_get_refcount(spa, &feature, &refcount) != 0) + continue; + + VERIFY0(nvlist_add_uint64(features, feature.fi_guid, refcount)); + } +} + +/* + * Store a list of pool features and their reference counts in the + * config. + * + * The first time this is called on a spa, allocate a new nvlist, fetch + * the pool features and reference counts from disk, then save the list + * in the spa. In subsequent calls on the same spa use the saved nvlist + * and refresh its values from the cached reference counts. This + * ensures we don't block here on I/O on a suspended pool so 'zpool + * clear' can resume the pool. + */ +static void +spa_add_feature_stats(spa_t *spa, nvlist_t *config) +{ + nvlist_t *features = spa->spa_feat_stats; + + ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER)); + + if (features != NULL) { + spa_feature_stats_from_cache(spa, features); + } else { + VERIFY0(nvlist_alloc(&features, NV_UNIQUE_NAME, KM_SLEEP)); + spa->spa_feat_stats = features; + spa_feature_stats_from_disk(spa, features); + } + + VERIFY0(nvlist_add_nvlist(config, ZPOOL_CONFIG_FEATURE_STATS, + features)); } int diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c index ce6f02dc4..ec0c01959 100644 --- a/module/zfs/spa_misc.c +++ b/module/zfs/spa_misc.c @@ -643,6 +643,7 @@ spa_remove(spa_t *spa) nvlist_free(spa->spa_label_features); nvlist_free(spa->spa_load_info); + nvlist_free(spa->spa_feat_stats); spa_config_set(spa, NULL); refcount_destroy(&spa->spa_refcount); diff --git a/module/zfs/zfeature.c b/module/zfs/zfeature.c index e6cab2c03..352376f22 100644 --- a/module/zfs/zfeature.c +++ b/module/zfs/zfeature.c @@ -228,7 +228,7 @@ spa_features_check(spa_t *spa, boolean_t for_write, * * Note: well-designed features will not need to use this; they should * use spa_feature_is_enabled() and spa_feature_is_active() instead. - * However, this is non-static for zdb and zhack. + * However, this is non-static for zdb, zhack, and spa_add_feature_stats(). */ int feature_get_refcount(spa_t *spa, zfeature_info_t *feature, uint64_t *res)