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mdbx: check-and-retry a mvcc-snapshot for unified page/buffer cache coherency.

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Part 1 of 2 of the workaround for https://github.com/erthink/libmdbx/issues/269.
This commit is contained in:
Леонид Юрьев (Leonid Yuriev) 2022-03-06 09:37:14 +03:00
parent f84d9f6208
commit 00ed61c685
1 changed files with 140 additions and 2 deletions
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142
src/core.c
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@ -3762,6 +3762,8 @@ static int __must_check_result mdbx_page_split(MDBX_cursor *mc,
MDBX_val *const newdata,
pgno_t newpgno, unsigned nflags);
static bool meta_checktxnid(const MDBX_env *env, const MDBX_meta *meta,
bool report);
static int __must_check_result mdbx_validate_meta_copy(MDBX_env *env,
const MDBX_meta *meta,
MDBX_meta *dest);
@ -6271,6 +6273,8 @@ static int mdbx_meta_unsteady(MDBX_env *env, const txnid_t last_steady,
else
return mdbx_pwrite(fd, &wipe, sizeof(meta->mm_datasync_sign),
(uint8_t *)&meta->mm_datasync_sign - env->me_map);
if (constmeta_txnid(env, meta) == last_steady)
mdbx_assert(env, meta_checktxnid(env, meta, true));
}
return MDBX_SUCCESS;
}
@ -7548,6 +7552,102 @@ __cold int mdbx_thread_unregister(const MDBX_env *env) {
return MDBX_SUCCESS;
}
/* check against https://github.com/erthink/libmdbx/issues/269 */
static bool meta_checktxnid(const MDBX_env *env, const MDBX_meta *meta,
bool report) {
const txnid_t meta_txnid = constmeta_txnid(env, meta);
const txnid_t freedb_mod_txnid = meta->mm_dbs[FREE_DBI].md_mod_txnid;
const txnid_t maindb_mod_txnid = meta->mm_dbs[MAIN_DBI].md_mod_txnid;
const pgno_t freedb_root_pgno = meta->mm_dbs[FREE_DBI].md_root;
const MDBX_page *freedb_root = (env->me_map && freedb_root_pgno != P_INVALID)
? pgno2page(env, freedb_root_pgno)
: nullptr;
const pgno_t maindb_root_pgno = meta->mm_dbs[MAIN_DBI].md_root;
const MDBX_page *maindb_root = (env->me_map && maindb_root_pgno != P_INVALID)
? pgno2page(env, maindb_root_pgno)
: nullptr;
const uint64_t magic_and_version =
unaligned_peek_u64(4, &meta->mm_magic_and_version);
bool ok = true;
if (unlikely(meta_txnid < freedb_mod_txnid ||
(!freedb_mod_txnid && freedb_root &&
likely(magic_and_version == MDBX_DATA_MAGIC)))) {
if (report)
mdbx_warning(
"catch invalid %sdb_mod_txnid %" PRIaTXN " for meta_txnid %" PRIaTXN
"%s",
"free", freedb_mod_txnid, meta_txnid,
"(workaround for incoherent flaw of unified page/buffer cache)");
ok = false;
}
if (unlikely(meta_txnid < maindb_mod_txnid ||
(!maindb_mod_txnid && maindb_root &&
likely(magic_and_version == MDBX_DATA_MAGIC)))) {
if (report)
mdbx_warning(
"catch invalid %sdb_mod_txnid %" PRIaTXN " for meta_txnid %" PRIaTXN
" %s",
"main", maindb_mod_txnid, meta_txnid,
"(workaround for incoherent flaw of unified page/buffer cache)");
ok = false;
}
if (likely(freedb_root && freedb_mod_txnid)) {
const txnid_t root_txnid = freedb_root->mp_txnid;
if (unlikely(root_txnid != freedb_mod_txnid)) {
if (report)
mdbx_warning(
"catch invalid root_page_txnid %" PRIaTXN
" for %sdb_mod_txnid %" PRIaTXN " %s",
root_txnid, "free", maindb_mod_txnid,
"(workaround for incoherent flaw of unified page/buffer cache)");
ok = false;
}
}
if (likely(maindb_root && maindb_mod_txnid)) {
const txnid_t root_txnid = maindb_root->mp_txnid;
if (unlikely(root_txnid != maindb_mod_txnid)) {
if (report)
mdbx_warning(
"catch invalid root_page_txnid %" PRIaTXN
" for %sdb_mod_txnid %" PRIaTXN " %s",
root_txnid, "main", maindb_mod_txnid,
"(workaround for incoherent flaw of unified page/buffer cache)");
ok = false;
}
}
return ok;
}
/* check with timeout as the workaround
* for https://github.com/erthink/libmdbx/issues/269 */
static int meta_waittxnid(const MDBX_env *env, const MDBX_meta *meta,
uint64_t *timestamp) {
if (likely(meta_checktxnid(env, (const MDBX_meta *)meta, !*timestamp)))
return MDBX_SUCCESS;
if (!*timestamp)
*timestamp = mdbx_osal_monotime();
else if (unlikely(mdbx_osal_monotime() - *timestamp > 65536 / 10)) {
mdbx_error("bailout waiting for valid snapshot %s",
"(workaround for incoherent flaw of unified page/buffer cache)");
return MDBX_CORRUPTED;
}
#if defined(_WIN32) || defined(_WIN64)
SwitchToThread();
#elif defined(__linux__) || defined(__gnu_linux__) || defined(_UNIX03_SOURCE)
sched_yield();
#elif (defined(_GNU_SOURCE) && __GLIBC_PREREQ(2, 1)) || defined(_OPEN_THREADS)
pthread_yield();
#else
usleep(42);
#endif
return MDBX_RESULT_TRUE;
}
/* Common code for mdbx_txn_begin() and mdbx_txn_renew(). */
static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
MDBX_env *env = txn->mt_env;
@ -7623,6 +7723,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
/* Seek & fetch the last meta */
if (likely(/* not recovery mode */ env->me_stuck_meta < 0)) {
uint64_t timestamp = 0;
while (1) {
volatile const MDBX_meta *const meta = meta_prefer_last(env);
mdbx_jitter4testing(false);
@ -7644,6 +7745,8 @@ static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
mdbx_assert(env, r->mr_txnid.weak == snap);
atomic_store32(&env->me_lck->mti_readers_refresh_flag, true,
mo_AcquireRelease);
} else {
/* exclusive mode without lck */
}
mdbx_jitter4testing(true);
@ -7664,8 +7767,14 @@ static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
snap == meta_txnid(env, meta) &&
snap >= atomic_load64(&env->me_lck->mti_oldest_reader,
mo_AcquireRelease))) {
/* workaround for https://github.com/erthink/libmdbx/issues/269 */
rc = meta_waittxnid(env, (const MDBX_meta *)meta, &timestamp);
mdbx_jitter4testing(false);
break;
if (likely(rc == MDBX_SUCCESS))
break;
if (likely(rc == MDBX_RESULT_TRUE))
continue;
goto bailout;
}
}
} else {
@ -7745,6 +7854,14 @@ static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
mdbx_jitter4testing(false);
const MDBX_meta *meta = constmeta_prefer_last(env);
uint64_t timestamp = 0;
while ("workaround for https://github.com/erthink/libmdbx/issues/269") {
rc = meta_waittxnid(env, (const MDBX_meta *)meta, &timestamp);
if (likely(rc == MDBX_SUCCESS))
break;
if (unlikely(rc != MDBX_RESULT_TRUE))
goto bailout;
}
mdbx_jitter4testing(false);
txn->mt_canary = meta->mm_canary;
const txnid_t snap = constmeta_txnid(env, meta);
@ -10730,6 +10847,7 @@ __cold static MDBX_page *mdbx_meta_model(const MDBX_env *env, MDBX_page *model,
model_meta->mm_dbs[MAIN_DBI].md_root = P_INVALID;
meta_set_txnid(env, model_meta, MIN_TXNID + num);
unaligned_poke_u64(4, model_meta->mm_datasync_sign, meta_sign(model_meta));
mdbx_assert(env, meta_checktxnid(env, model_meta, true));
return (MDBX_page *)((uint8_t *)model + env->me_psize);
}
@ -10892,6 +11010,7 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
goto fail;
}
meta_set_txnid(env, pending, txnid);
mdbx_assert(env, meta_checktxnid(env, pending, true));
}
}
}
@ -10924,6 +11043,7 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
rc = (flags & MDBX_SAFE_NOSYNC) ? MDBX_RESULT_TRUE /* carry non-steady */
: MDBX_RESULT_FALSE /* carry steady */;
}
mdbx_assert(env, meta_checktxnid(env, pending, true));
/* Steady or Weak */
if (rc == MDBX_RESULT_FALSE /* carry steady */) {
@ -11032,6 +11152,7 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
/* LY: 'commit' the meta */
meta_update_end(env, target, unaligned_peek_u64(4, pending->mm_txnid_b));
mdbx_jitter4testing(true);
mdbx_assert(env, meta_checktxnid(env, target, true));
} else {
/* dangerous case (target == head), only mm_datasync_sign could
* me updated, check assertions once again */
@ -11081,6 +11202,7 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
if (rc != MDBX_SUCCESS)
goto undo;
}
mdbx_assert(env, meta_checktxnid(env, target, true));
}
env->me_lck->mti_meta_sync_txnid.weak =
(uint32_t)unaligned_peek_u64(4, pending->mm_txnid_a) -
@ -11094,6 +11216,7 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
pending->mm_geo.upper);
if (MDBX_IS_ERROR(rc))
goto fail;
mdbx_assert(env, meta_checktxnid(env, target, true));
}
MDBX_lockinfo *const lck = env->me_lck_mmap.lck;
@ -11552,7 +11675,16 @@ mdbx_env_set_geometry(MDBX_env *env, intptr_t size_lower, intptr_t size_now,
if (!inside_txn) {
mdbx_assert(env, need_unlock);
const MDBX_meta *head = constmeta_prefer_last(env);
meta = *head;
uint64_t timestamp = 0;
while ("workaround for https://github.com/erthink/libmdbx/issues/269") {
meta = *head;
rc = meta_waittxnid(env, &meta, &timestamp);
if (likely(rc == MDBX_SUCCESS))
break;
if (unlikely(rc != MDBX_RESULT_TRUE))
goto bailout;
}
const txnid_t txnid = safe64_txnid_next(constmeta_txnid(env, &meta));
if (unlikely(txnid > MAX_TXNID)) {
rc = MDBX_TXN_FULL;
@ -12455,7 +12587,9 @@ __cold static int __must_check_result mdbx_override_meta(
mdbx_meta_model(env, page, target);
MDBX_meta *const model = page_meta(page);
meta_set_txnid(env, model, txnid);
mdbx_assert(env, meta_checktxnid(env, model, true));
if (shape) {
mdbx_assert(env, meta_checktxnid(env, shape, true));
model->mm_extra_flags = shape->mm_extra_flags;
model->mm_validator_id = shape->mm_validator_id;
model->mm_extra_pagehdr = shape->mm_extra_pagehdr;
@ -12464,6 +12598,7 @@ __cold static int __must_check_result mdbx_override_meta(
memcpy(&model->mm_canary, &shape->mm_canary, sizeof(model->mm_canary));
memcpy(&model->mm_pages_retired, &shape->mm_pages_retired,
sizeof(model->mm_pages_retired));
mdbx_assert(env, meta_checktxnid(env, model, true));
}
unaligned_poke_u64(4, model->mm_datasync_sign, meta_sign(model));
rc = mdbx_validate_meta(env, model, page, target, nullptr);
@ -17367,6 +17502,7 @@ static int mdbx_rebalance(MDBX_cursor *mc) {
if (nkeys == 0) {
mdbx_cassert(mc, IS_LEAF(mp));
mdbx_debug("%s", "tree is completely empty");
mdbx_cassert(mc, (*mc->mc_dbistate & DBI_DIRTY) != 0);
mc->mc_db->md_root = P_INVALID;
mc->mc_db->md_depth = 0;
mdbx_cassert(mc, mc->mc_db->md_branch_pages == 0 &&
@ -20172,6 +20308,7 @@ static int dbi_open(MDBX_txn *txn, const char *table_name, unsigned user_flags,
dbiflags |= DBI_DIRTY | DBI_CREAT;
txn->mt_flags |= MDBX_TXN_DIRTY;
mdbx_tassert(txn, (txn->mt_dbistate[MAIN_DBI] & DBI_DIRTY) != 0);
}
/* Got info, register DBI in this txn */
@ -20459,6 +20596,7 @@ int mdbx_drop(MDBX_txn *txn, MDBX_dbi dbi, bool del) {
txn->mt_dbs[dbi].md_entries = 0;
txn->mt_dbs[dbi].md_root = P_INVALID;
txn->mt_dbs[dbi].md_seq = 0;
/* txn->mt_dbs[dbi].md_mod_txnid = txn->mt_txnid; */
txn->mt_flags |= MDBX_TXN_DIRTY;
}