diff --git a/include/sys/ddt.h b/include/sys/ddt.h index ce20da6b0f..b29667e5ab 100644 --- a/include/sys/ddt.h +++ b/include/sys/ddt.h @@ -117,6 +117,10 @@ enum ddt_phys_type { /* * In-core ddt entry */ + +/* State flags for dde_flags */ +#define DDE_FLAG_LOADED (1 << 0) /* entry ready for use */ + typedef struct { /* key must be first for ddt_key_compare */ ddt_key_t dde_key; @@ -125,8 +129,7 @@ typedef struct { struct abd *dde_repair_abd; ddt_type_t dde_type; ddt_class_t dde_class; - uint8_t dde_loading; - uint8_t dde_loaded; + uint8_t dde_flags; kcondvar_t dde_cv; avl_node_t dde_node; } ddt_entry_t; diff --git a/module/zfs/ddt.c b/module/zfs/ddt.c index df79de74e3..3e278d702d 100644 --- a/module/zfs/ddt.c +++ b/module/zfs/ddt.c @@ -448,7 +448,7 @@ ddt_alloc(const ddt_key_t *ddk) static void ddt_free(ddt_entry_t *dde) { - ASSERT(!dde->dde_loading); + ASSERT(dde->dde_flags & DDE_FLAG_LOADED); for (int p = 0; p < DDT_PHYS_TYPES; p++) ASSERT3P(dde->dde_lead_zio[p], ==, NULL); @@ -483,26 +483,37 @@ ddt_lookup(ddt_t *ddt, const blkptr_t *bp, boolean_t add) ddt_key_fill(&search, bp); + /* Find an existing live entry */ dde = avl_find(&ddt->ddt_tree, &search, &where); - if (dde == NULL) { - if (!add) - return (NULL); - dde = ddt_alloc(&search); - avl_insert(&ddt->ddt_tree, dde, where); + if (dde != NULL) { + /* Found it. If it's already loaded, we can just return it. */ + if (dde->dde_flags & DDE_FLAG_LOADED) + return (dde); + + /* Someone else is loading it, wait for it. */ + while (!(dde->dde_flags & DDE_FLAG_LOADED)) + cv_wait(&dde->dde_cv, &ddt->ddt_lock); + + return (dde); } - while (dde->dde_loading) - cv_wait(&dde->dde_cv, &ddt->ddt_lock); + /* Not found. */ + if (!add) + return (NULL); - if (dde->dde_loaded) - return (dde); - - dde->dde_loading = B_TRUE; + /* Time to make a new entry. */ + dde = ddt_alloc(&search); + avl_insert(&ddt->ddt_tree, dde, where); + /* + * ddt_tree is now stable, so unlock and let everyone else keep moving. + * Anyone landing on this entry will find it without DDE_FLAG_LOADED, + * and go to sleep waiting for it above. + */ ddt_exit(ddt); + /* Search all store objects for the entry. */ error = ENOENT; - for (type = 0; type < DDT_TYPES; type++) { for (class = 0; class < DDT_CLASSES; class++) { error = ddt_object_lookup(ddt, type, class, dde); @@ -517,17 +528,16 @@ ddt_lookup(ddt_t *ddt, const blkptr_t *bp, boolean_t add) ddt_enter(ddt); - ASSERT(!dde->dde_loaded); - ASSERT(dde->dde_loading); + ASSERT(!(dde->dde_flags & DDE_FLAG_LOADED)); dde->dde_type = type; /* will be DDT_TYPES if no entry found */ dde->dde_class = class; /* will be DDT_CLASSES if no entry found */ - dde->dde_loaded = B_TRUE; - dde->dde_loading = B_FALSE; if (error == 0) ddt_stat_update(ddt, dde, -1ULL); + /* Entry loaded, everyone can proceed now */ + dde->dde_flags |= DDE_FLAG_LOADED; cv_broadcast(&dde->dde_cv); return (dde); @@ -812,8 +822,7 @@ ddt_sync_entry(ddt_t *ddt, ddt_entry_t *dde, dmu_tx_t *tx, uint64_t txg) ddt_class_t nclass; uint64_t total_refcnt = 0; - ASSERT(dde->dde_loaded); - ASSERT(!dde->dde_loading); + ASSERT(dde->dde_flags & DDE_FLAG_LOADED); for (int p = 0; p < DDT_PHYS_TYPES; p++, ddp++) { ASSERT3P(dde->dde_lead_zio[p], ==, NULL);