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ITS#8704 add MDB_PREVSNAPSHOT flag to mdb_env_open

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used to open the previous snapshot, in case the latest one
is corrupted
This commit is contained in:
Howard Chu 2017-08-12 12:21:25 +01:00
parent 86226754a9
commit 9c6eb75c65
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GPG key ID: FD2A70B44AB11BA7
8 changed files with 68 additions and 15 deletions
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41
external/db_drivers/liblmdb/mdb.c vendored
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@ -1468,7 +1468,7 @@ static int mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst);
static int mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata,
pgno_t newpgno, unsigned int nflags);
static int mdb_env_read_header(MDB_env *env, MDB_meta *meta);
static int mdb_env_read_header(MDB_env *env, int prev, MDB_meta *meta);
static MDB_meta *mdb_env_pick_meta(const MDB_env *env);
static int mdb_env_write_meta(MDB_txn *txn);
#ifdef MDB_USE_POSIX_MUTEX /* Drop unused excl arg */
@ -3632,6 +3632,8 @@ done:
return MDB_SUCCESS;
}
static int ESECT mdb_env_share_locks(MDB_env *env, int *excl);
int
mdb_txn_commit(MDB_txn *txn)
{
@ -3854,6 +3856,15 @@ mdb_txn_commit(MDB_txn *txn)
if ((rc = mdb_env_write_meta(txn)))
goto fail;
end_mode = MDB_END_COMMITTED|MDB_END_UPDATE;
if (env->me_flags & MDB_PREVSNAPSHOT) {
if (!(env->me_flags & MDB_NOLOCK)) {
int excl;
rc = mdb_env_share_locks(env, &excl);
if (rc)
goto fail;
}
env->me_flags ^= MDB_PREVSNAPSHOT;
}
done:
mdb_txn_end(txn, end_mode);
@ -3867,11 +3878,12 @@ fail:
/** Read the environment parameters of a DB environment before
* mapping it into memory.
* @param[in] env the environment handle
* @param[in] prev whether to read the backup meta page
* @param[out] meta address of where to store the meta information
* @return 0 on success, non-zero on failure.
*/
static int ESECT
mdb_env_read_header(MDB_env *env, MDB_meta *meta)
mdb_env_read_header(MDB_env *env, int prev, MDB_meta *meta)
{
MDB_metabuf pbuf;
MDB_page *p;
@ -3922,7 +3934,7 @@ mdb_env_read_header(MDB_env *env, MDB_meta *meta)
return MDB_VERSION_MISMATCH;
}
if (off == 0 || m->mm_txnid > meta->mm_txnid)
if (off == 0 || (prev ? m->mm_txnid < meta->mm_txnid : m->mm_txnid > meta->mm_txnid))
*meta = *m;
}
return 0;
@ -4131,7 +4143,8 @@ static MDB_meta *
mdb_env_pick_meta(const MDB_env *env)
{
MDB_meta *const *metas = env->me_metas;
return metas[ metas[0]->mm_txnid < metas[1]->mm_txnid ];
return metas[ (metas[0]->mm_txnid < metas[1]->mm_txnid) ^
((env->me_flags & MDB_PREVSNAPSHOT) != 0) ];
}
int ESECT
@ -4366,7 +4379,7 @@ mdb_fsize(HANDLE fd, mdb_size_t *size)
/** Further setup required for opening an LMDB environment
*/
static int ESECT
mdb_env_open2(MDB_env *env)
mdb_env_open2(MDB_env *env, int prev)
{
unsigned int flags = env->me_flags;
int i, newenv = 0, rc;
@ -4429,7 +4442,7 @@ mdb_env_open2(MDB_env *env)
}
#endif
if ((i = mdb_env_read_header(env, &meta)) != 0) {
if ((i = mdb_env_read_header(env, prev, &meta)) != 0) {
if (i != ENOENT)
return i;
DPUTS("new mdbenv");
@ -4505,6 +4518,9 @@ mdb_env_open2(MDB_env *env)
#endif
env->me_maxpg = env->me_mapsize / env->me_psize;
if (env->me_txns)
env->me_txns->mti_txnid = meta.mm_txnid;
#if MDB_DEBUG
{
MDB_meta *meta = mdb_env_pick_meta(env);
@ -4600,9 +4616,6 @@ static int ESECT
mdb_env_share_locks(MDB_env *env, int *excl)
{
int rc = 0;
MDB_meta *meta = mdb_env_pick_meta(env);
env->me_txns->mti_txnid = meta->mm_txnid;
#ifdef _WIN32
{
@ -5056,7 +5069,7 @@ fail:
*/
#define CHANGEABLE (MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_NOMEMINIT)
#define CHANGELESS (MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY| \
MDB_WRITEMAP|MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD)
MDB_WRITEMAP|MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD|MDB_PREVSNAPSHOT)
#if VALID_FLAGS & PERSISTENT_FLAGS & (CHANGEABLE|CHANGELESS)
# error "Persistent DB flags & env flags overlap, but both go in mm_flags"
@ -5178,9 +5191,13 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
rc = mdb_env_setup_locks(env, lpath, mode, &excl);
if (rc)
goto leave;
if ((flags & MDB_PREVSNAPSHOT) && !excl) {
rc = EAGAIN;
goto leave;
}
}
if ((rc = mdb_env_open2(env)) == MDB_SUCCESS) {
if ((rc = mdb_env_open2(env, flags & MDB_PREVSNAPSHOT)) == MDB_SUCCESS) {
if (flags & (MDB_RDONLY|MDB_WRITEMAP)) {
env->me_mfd = env->me_fd;
} else {
@ -5206,7 +5223,7 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
}
}
DPRINTF(("opened dbenv %p", (void *) env));
if (excl > 0) {
if (excl > 0 && !(flags & MDB_PREVSNAPSHOT)) {
rc = mdb_env_share_locks(env, &excl);
if (rc)
goto leave;