From 3daab3be733b933a3fd2263441da4976206b27a2 Mon Sep 17 00:00:00 2001 From: moneromooo-monero Date: Mon, 31 Jul 2017 00:04:28 +0100 Subject: [PATCH] ITS#8704 add MDB_PREVMETA flag to mdb_env_open used to open the previous meta page, in case the latest one is corrupted From https://github.com/LMDB/lmdb/pull/12 --- libraries/liblmdb/lmdb.h | 6 ++++++ libraries/liblmdb/mdb.c | 15 ++++++++------- 2 files changed, 14 insertions(+), 7 deletions(-) diff --git a/libraries/liblmdb/lmdb.h b/libraries/liblmdb/lmdb.h index 039210d..0a10fc9 100644 --- a/libraries/liblmdb/lmdb.h +++ b/libraries/liblmdb/lmdb.h @@ -332,6 +332,8 @@ typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *rel #define MDB_NORDAHEAD 0x800000 /** don't initialize malloc'd memory before writing to datafile */ #define MDB_NOMEMINIT 0x1000000 + /** use the previous meta page rather than the latest one */ +#define MDB_PREVMETA 0x2000000 /** @} */ /** @defgroup mdb_dbi_open Database Flags @@ -646,6 +648,10 @@ int mdb_env_create(MDB_env **env); * caller is expected to overwrite all of the memory that was * reserved in that case. * This flag may be changed at any time using #mdb_env_set_flags(). + *
  • #MDB_PREVMETA + * Open the environment with the previous meta page rather than the latest + * one. This loses the latest transaction, but may help work around some + * types of corruption. * * @param[in] mode The UNIX permissions to set on created files and semaphores. * This parameter is ignored on Windows. diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c index 148dc45..94081ca 100644 --- a/libraries/liblmdb/mdb.c +++ b/libraries/liblmdb/mdb.c @@ -1582,7 +1582,7 @@ 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 */ @@ -3985,11 +3985,12 @@ 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; @@ -4040,7 +4041,7 @@ 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; @@ -4670,7 +4671,7 @@ mdb_fopen(const MDB_env *env, MDB_name *fname, /** 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; @@ -4733,7 +4734,7 @@ 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"); @@ -5332,7 +5333,7 @@ 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_PREVMETA) #if VALID_FLAGS & PERSISTENT_FLAGS & (CHANGEABLE|CHANGELESS) # error "Persistent DB flags & env flags overlap, but both go in mm_flags" @@ -5432,7 +5433,7 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode goto leave; } - if ((rc = mdb_env_open2(env)) == MDB_SUCCESS) { + if ((rc = mdb_env_open2(env, flags & MDB_PREVMETA)) == MDB_SUCCESS) { if (!(flags & (MDB_RDONLY|MDB_WRITEMAP))) { /* Synchronous fd for meta writes. Needed even with * MDB_NOSYNC/MDB_NOMETASYNC, in case these get reset.