Only set me_mfd if needed. Drop unused read access.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index e2f1bbca1d23c19cf81b2db36a36f86402f2c6ab..fe7f6888e8c9a6cd840ab3498a14c16933fb5f58 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -1239,7 +1239,7 @@ typedef struct MDB_pgstate {
 struct MDB_env {
        HANDLE          me_fd;          /**< The main data file */
        HANDLE          me_lfd;         /**< The lock file */
-       HANDLE          me_mfd;                 /**< just for writing the meta pages */
+       HANDLE          me_mfd;         /**< For writing and syncing the meta pages */
        /** Failed to update the meta page. Probably an I/O error. */
 #define        MDB_FATAL_ERROR 0x80000000U
        /** Some fields are initialized. */
@@ -3827,7 +3827,10 @@ mdb_env_write_meta(MDB_txn *txn)
        len = sizeof(MDB_meta) - off;
        off += (char *)mp - env->me_map;
 
-       /* Write to the SYNC fd */
+       /* Write to the SYNC fd unless MDB_NOSYNC/MDB_NOMETASYNC.
+        * (me_mfd goes to the same file as me_fd, but writing to it
+        * also syncs to disk.  Avoids a separate fdatasync() call.)
+        */
        mfd = (flags & (MDB_NOSYNC|MDB_NOMETASYNC)) ? env->me_fd : env->me_mfd;
 #ifdef _WIN32
        {
@@ -4156,7 +4159,7 @@ enum mdb_fopen_type {
        /* A comment in mdb_fopen() explains some O_* flag choices. */
        MDB_O_RDONLY= O_RDONLY,                            /**< for RDONLY me_fd */
        MDB_O_RDWR  = O_RDWR  |O_CREAT,                    /**< for me_fd */
-       MDB_O_META  = O_RDWR  |MDB_DSYNC     |MDB_CLOEXEC, /**< for me_mfd */
+       MDB_O_META  = O_WRONLY|MDB_DSYNC     |MDB_CLOEXEC, /**< for me_mfd */
        MDB_O_COPY  = O_WRONLY|O_CREAT|O_EXCL|MDB_CLOEXEC, /**< for #mdb_env_copy() */
        /** Bitmask for open() flags in enum #mdb_fopen_type.  The other bits
         * distinguish otherwise-equal MDB_O_* constants from each other.
@@ -4217,6 +4220,7 @@ mdb_fopen(const MDB_env *env, MDB_name *fname,
                disp = OPEN_EXISTING;
                break;
        case MDB_O_META:                        /* for writing metapages */
+               acc = GENERIC_WRITE;
                disp = OPEN_EXISTING;
                attrs = FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH;
                break;
@@ -4955,9 +4959,7 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
        }
 
        if ((rc = mdb_env_open2(env)) == MDB_SUCCESS) {
-               if (flags & (MDB_RDONLY|MDB_WRITEMAP)) {
-                       env->me_mfd = env->me_fd;
-               } else {
+               if (!(flags & (MDB_RDONLY|MDB_WRITEMAP))) {
                        /* Synchronous fd for meta writes. Needed even with
                         * MDB_NOSYNC/MDB_NOMETASYNC, in case these get reset.
                         */
@@ -5040,7 +5042,7 @@ mdb_env_close0(MDB_env *env, int excl)
        if (env->me_map) {
                munmap(env->me_map, env->me_mapsize);
        }
-       if (env->me_mfd != env->me_fd && env->me_mfd != INVALID_HANDLE_VALUE)
+       if (env->me_mfd != INVALID_HANDLE_VALUE)
                (void) close(env->me_mfd);
        if (env->me_fd != INVALID_HANDLE_VALUE)
                (void) close(env->me_fd);