Add MDB_WRITEMAP to use a writable mmap

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index 3b3e046..79e8423 100644 (file)
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -1312,26 +1312,39 @@ none:
                        return NULL;
                }
        }
-       if (txn->mt_env->me_dpages && num == 1) {
-               np = txn->mt_env->me_dpages;
-               VGMEMP_ALLOC(txn->mt_env, np, txn->mt_env->me_psize);
-               VGMEMP_DEFINED(np, sizeof(np->mp_next));
-               txn->mt_env->me_dpages = np->mp_next;
-       } else {
-               size_t sz = txn->mt_env->me_psize * num;
-               if ((np = malloc(sz)) == NULL)
-                       return NULL;
-               VGMEMP_ALLOC(txn->mt_env, np, sz);
-       }
-       if (pgno == P_INVALID) {
-               np->mp_pgno = txn->mt_next_pgno;
-               txn->mt_next_pgno += num;
-       } else {
+       if (txn->mt_env->me_flags & MDB_WRITEMAP) {
+               if (pgno == P_INVALID) {
+                       pgno = txn->mt_next_pgno;
+                       txn->mt_next_pgno += num;
+               }
+               np = (MDB_page *)(txn->mt_env->me_map + txn->mt_env->me_psize * pgno);
                np->mp_pgno = pgno;
+       } else {
+               if (txn->mt_env->me_dpages && num == 1) {
+                       np = txn->mt_env->me_dpages;
+                       VGMEMP_ALLOC(txn->mt_env, np, txn->mt_env->me_psize);
+                       VGMEMP_DEFINED(np, sizeof(np->mp_next));
+                       txn->mt_env->me_dpages = np->mp_next;
+               } else {
+                       size_t sz = txn->mt_env->me_psize * num;
+                       if ((np = malloc(sz)) == NULL)
+                               return NULL;
+                       VGMEMP_ALLOC(txn->mt_env, np, sz);
+               }
+               if (pgno == P_INVALID) {
+                       np->mp_pgno = txn->mt_next_pgno;
+                       txn->mt_next_pgno += num;
+               } else {
+                       np->mp_pgno = pgno;
+               }
        }
        mid.mid = np->mp_pgno;
        mid.mptr = np;
-       mdb_mid2l_insert(txn->mt_u.dirty_list, &mid);
+       if (txn->mt_env->me_flags & MDB_WRITEMAP) {
+               mdb_mid2l_append(txn->mt_u.dirty_list, &mid);
+       } else {
+               mdb_mid2l_insert(txn->mt_u.dirty_list, &mid);
+       }
 
        return np;
 }
@@ -1655,6 +1668,9 @@ mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
                if (parent->mt_child) {
                        return EINVAL;
                }
+               /* nested TXNs not supported here */
+               if (env->me_flags & MDB_WRITEMAP)
+                       return EINVAL;
        }
        size = sizeof(MDB_txn) + env->me_maxdbs * (sizeof(MDB_db)+1);
        if (!(flags & MDB_RDONLY))
@@ -1741,17 +1757,19 @@ mdb_txn_reset0(MDB_txn *txn)
                        }
                }
 
-               /* return all dirty pages to dpage list */
-               for (i=1; i<=txn->mt_u.dirty_list[0].mid; i++) {
-                       dp = txn->mt_u.dirty_list[i].mptr;
-                       if (!IS_OVERFLOW(dp) || dp->mp_pages == 1) {
-                               dp->mp_next = txn->mt_env->me_dpages;
-                               VGMEMP_FREE(txn->mt_env, dp);
-                               txn->mt_env->me_dpages = dp;
-                       } else {
-                               /* large pages just get freed directly */
-                               VGMEMP_FREE(txn->mt_env, dp);
-                               free(dp);
+               if (!(env->me_flags & MDB_WRITEMAP)) {
+                       /* return all dirty pages to dpage list */
+                       for (i=1; i<=txn->mt_u.dirty_list[0].mid; i++) {
+                               dp = txn->mt_u.dirty_list[i].mptr;
+                               if (!IS_OVERFLOW(dp) || dp->mp_pages == 1) {
+                                       dp->mp_next = txn->mt_env->me_dpages;
+                                       VGMEMP_FREE(txn->mt_env, dp);
+                                       txn->mt_env->me_dpages = dp;
+                               } else {
+                                       /* large pages just get freed directly */
+                                       VGMEMP_FREE(txn->mt_env, dp);
+                                       free(dp);
+                               }
                        }
                }
 
@@ -2057,6 +2075,17 @@ again:
        mdb_audit(txn);
 #endif
 
+       if (env->me_flags & MDB_WRITEMAP) {
+               for (i=1; i<=txn->mt_u.dirty_list[0].mid; i++) {
+                       dp = txn->mt_u.dirty_list[i].mptr;
+                       /* clear dirty flag */
+                       dp->mp_flags &= ~P_DIRTY;
+                       txn->mt_u.dirty_list[i].mid = 0;
+               }
+               txn->mt_u.dirty_list[0].mid = 0;
+               goto sync;
+       }
+
        /* Commit up to MDB_COMMIT_PAGES dirty pages to disk until done.
         */
        next = 0;
@@ -2165,6 +2194,7 @@ again:
        }
        txn->mt_u.dirty_list[0].mid = 0;
 
+sync:
        if ((n = mdb_env_sync(env, 0)) != 0 ||
            (n = mdb_env_write_meta(txn)) != MDB_SUCCESS) {
                mdb_txn_abort(txn);
@@ -2323,6 +2353,14 @@ mdb_env_write_meta(MDB_txn *txn)
 
        env = txn->mt_env;
 
+       if (env->me_flags & MDB_WRITEMAP) {
+               MDB_meta *mp = env->me_metas[toggle];
+               mp->mm_dbs[0] = txn->mt_dbs[0];
+               mp->mm_dbs[1] = txn->mt_dbs[1];
+               mp->mm_last_pg = txn->mt_next_pgno - 1;
+               mp->mm_txnid = txn->mt_txnid;
+               goto done;
+       }
        metab.mm_txnid = env->me_metas[toggle]->mm_txnid;
        metab.mm_last_pg = env->me_metas[toggle]->mm_last_pg;
 
@@ -2368,6 +2406,7 @@ mdb_env_write_meta(MDB_txn *txn)
                env->me_flags |= MDB_FATAL_ERROR;
                return rc;
        }
+done:
        /* Memory ordering issues are irrelevant; since the entire writer
         * is wrapped by wmutex, all of these changes will become visible
         * after the wmutex is unlocked. Since the DB is multi-version,
@@ -2456,7 +2495,7 @@ mdb_env_get_maxreaders(MDB_env *env, unsigned int *readers)
 static int
 mdb_env_open2(MDB_env *env, unsigned int flags)
 {
-       int i, newenv = 0;
+       int i, newenv = 0, prot;
        MDB_meta meta;
        MDB_page *p;
 
@@ -2505,7 +2544,12 @@ mdb_env_open2(MDB_env *env, unsigned int flags)
        i = MAP_SHARED;
        if (meta.mm_address && (flags & MDB_FIXEDMAP))
                i |= MAP_FIXED;
-       env->me_map = mmap(meta.mm_address, env->me_mapsize, PROT_READ, i,
+       prot = PROT_READ;
+       if (flags & MDB_WRITEMAP) {
+               prot |= PROT_WRITE;
+               ftruncate(env->me_fd, env->me_mapsize);
+       }
+       env->me_map = mmap(meta.mm_address, env->me_mapsize, prot, i,
                env->me_fd, 0);
        if (env->me_map == MAP_FAILED) {
                env->me_map = NULL;
@@ -3434,6 +3478,11 @@ mdb_page_get(MDB_txn *txn, pgno_t pgno, MDB_page **ret)
 {
        MDB_page *p = NULL;
 
+       if (txn->mt_env->me_flags & MDB_WRITEMAP) {
+               if (pgno < txn->mt_next_pgno)
+                       p = (MDB_page *)(txn->mt_env->me_map + txn->mt_env->me_psize * pgno);
+               goto done;
+       }
        if (!F_ISSET(txn->mt_flags, MDB_TXN_RDONLY) && txn->mt_u.dirty_list[0].mid) {
                unsigned x;
                x = mdb_mid2l_search(txn->mt_u.dirty_list, pgno);
@@ -3445,6 +3494,7 @@ mdb_page_get(MDB_txn *txn, pgno_t pgno, MDB_page **ret)
                if (pgno < txn->mt_next_pgno)
                        p = (MDB_page *)(txn->mt_env->me_map + txn->mt_env->me_psize * pgno);
        }
+done:
        *ret = p;
        if (!p) {
                DPRINTF("page %zu not found", pgno);

diff --git a/libraries/libmdb/mdb.h b/libraries/libmdb/mdb.h
index ea857a0..db07f4b 100644 (file)
--- a/libraries/libmdb/mdb.h
+++ b/libraries/libmdb/mdb.h
@@ -161,6 +161,8 @@ typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *rel
 #define MDB_RDONLY             0x20000
        /** don't fsync metapage after commit */
 #define MDB_NOMETASYNC         0x40000
+       /** use writable mmap */
+#define MDB_WRITEMAP           0x80000
 /** @} */
 
 /**    @defgroup       mdb_open        Database Flags

diff --git a/libraries/libmdb/midl.c b/libraries/libmdb/midl.c
index a3844d6..9ee100d 100644 (file)
--- a/libraries/libmdb/midl.c
+++ b/libraries/libmdb/midl.c
@@ -311,5 +311,17 @@ int mdb_mid2l_insert( MDB_ID2L ids, MDB_ID2 *id )
 
        return 0;
 }
+
+int mdb_mid2l_append( MDB_ID2L ids, MDB_ID2 *id )
+{
+       /* Too big? */
+       if (ids[0].mid >= MDB_IDL_UM_MAX) {
+               return -2;
+       }
+       ids[0].mid++;
+       ids[ids[0].mid] = *id;
+       return 0;
+}
+
 /** @} */
 /** @} */

diff --git a/libraries/libmdb/midl.h b/libraries/libmdb/midl.h
index f072ca3..0fd1cfb 100644 (file)
--- a/libraries/libmdb/midl.h
+++ b/libraries/libmdb/midl.h
@@ -180,6 +180,13 @@ unsigned mdb_mid2l_search( MDB_ID2L ids, MDB_ID id );
         */
 int mdb_mid2l_insert( MDB_ID2L ids, MDB_ID2 *id );
 
+       /** Append an ID2 into a ID2L.
+        * @param[in,out] ids   The ID2L to append into.
+        * @param[in] id        The ID2 to append.
+        * @return      0 on success, -2 if the ID2L is too big.
+        */
+int mdb_mid2l_append( MDB_ID2L ids, MDB_ID2 *id );
+
 /** @} */
 /** @} */
 #ifdef __cplusplus