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Patch crash-consistency violations. #6

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Patch crash-consistency violations. #6

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847b37a
Add fixes for reported bugs.
iangneal Nov 4, 2021
9cf45a9
Fix typos
iangneal Nov 4, 2021
3a9bebe
Don't overwrite CAS ID on restart
iangneal Nov 4, 2021
b462d99
Fix it->data->cas persist ordering
iangneal Nov 4, 2021
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32 changes: 28 additions & 4 deletions items.c
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Original file line number Diff line number Diff line change
Expand Up @@ -117,8 +117,8 @@ static uint64_t lru_total_bumps_dropped(void);

/* Get the next CAS id for a new item. */
/* TODO: refactor some atomics for this. */
static uint64_t cas_id = 0;
uint64_t get_cas_id(void) {
static uint64_t cas_id = 0;
pthread_mutex_lock(&cas_id_lock);
uint64_t next_id = ++cas_id;
pthread_mutex_unlock(&cas_id_lock);
Expand Down Expand Up @@ -499,7 +499,22 @@ void do_item_relink(item *it, uint32_t hv) {
stats.total_items += 1;
STATS_UNLOCK();

ITEM_set_cas(it, (settings.use_cas) ? get_cas_id() : 0);
/* Use the persistent CAS ID */
uint64_t cas = ITEM_get_cas(it);
if (cas && !settings.use_cas) {
/* Force use of CAS IDs if the persistent slab has CAS IDs */
settings.use_cas = true;
if (settings.verbose > 2)
fprintf(stderr, "FORCING settings.use_cas=yes due to persistent state\n");
}

if (settings.use_cas && cas) {
/* Update the current CAS ID for future items */
cas_id = cas_id < cas ? cas : cas_id;
} else if (settings.use_cas) {
/* Otherwise, allocate a new CAS ID for all */
ITEM_set_cas(it, get_cas_id());
}
assoc_insert(it, hv);
item_link_q(it);
it->refcount = 1;
Expand All @@ -516,10 +531,17 @@ int do_item_link(item *it, const uint32_t hv) {
pslab_item_data_flush(it);
pmem_drain();

atomic_store(&it->it_flags, atomic_load(&it->it_flags) | ITEM_LINKED);
pmem_member_persist(it, it_flags);
/* Persist time to avoid false eviction on crash recovery */
it->time = current_time;
pmem_member_persist(it, time);

/* Allocate a new CAS ID before link so CAS ID is crash consistent */
ITEM_set_cas(it, (settings.use_cas) ? get_cas_id() : 0);
pmem_member_persist(it, data->cas);

/* Link item last for atomicity */
atomic_store(&it->it_flags, atomic_load(&it->it_flags) | ITEM_LINKED);
pmem_member_persist(it, it_flags);
} else {
#endif
atomic_store(&it->it_flags, atomic_load(&it->it_flags) | ITEM_LINKED);
Expand All @@ -534,8 +556,10 @@ int do_item_link(item *it, const uint32_t hv) {
stats.total_items += 1;
STATS_UNLOCK();

#ifndef PSLAB
/* Allocate a new CAS ID on link. */
ITEM_set_cas(it, (settings.use_cas) ? get_cas_id() : 0);
#endif
assoc_insert(it, hv);
item_link_q(it);
refcount_incr(it);
Expand Down