Use an environment directory

Go back to using an mmap'd lock file

diff --git a/libraries/libmdb/Makefile b/libraries/libmdb/Makefile
index 36e782b..4c30b23 100644 (file)
--- a/libraries/libmdb/Makefile
+++ b/libraries/libmdb/Makefile
@@ -7,9 +7,10 @@ LDLIBS =
 all:   mtest mdb_stat
 
 clean:
-       rm -f mtest mdb_stat *.[ao] *~ testdb
+       rm -rf mtest mdb_stat *.[ao] *~ testdb
 
 test:  all
+       mkdir testdb
        ./mtest && ./mdb_stat testdb
 
 mdb_stat: mdb_stat.o mdb.o idl.o

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index 147274f..b5a9e33 100644 (file)
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -7,8 +7,7 @@
 #ifdef HAVE_SYS_FILE_H
 #include <sys/file.h>
 #endif
-#include <sys/ipc.h>
-#include <sys/shm.h>
+#include <fcntl.h>
 
 #include <assert.h>
 #include <err.h>
@@ -218,6 +217,7 @@ struct MDB_txn {
        } mt_u;
 #define MDB_TXN_RDONLY          0x01           /* read-only transaction */
 #define MDB_TXN_ERROR           0x02           /* an error has occurred */
+#define MDB_TXN_METOGGLE       0x04            /* used meta page 1 */
        unsigned int             mt_flags;
 };
 
@@ -233,10 +233,9 @@ struct MDB_db {
 
 struct MDB_env {
        int                     me_fd;
-       key_t           me_shmkey;
+       int                     me_lfd;
        uint32_t        me_flags;
-       int                     me_maxreaders;
-       int                     me_metatoggle;
+       unsigned int                    me_maxreaders;
        char            *me_path;
        char *me_map;
        MDB_txninfo     *me_txns;
@@ -274,7 +273,7 @@ static int  mdb_search_page(MDB_db *db,
 
 static int  mdbenv_read_header(MDB_env *env);
 static int  mdb_check_meta_page(MDB_page *p);
-static int  mdbenv_read_meta(MDB_env *env);
+static int  mdbenv_read_meta(MDB_env *env, int *which);
 static int  mdbenv_write_meta(MDB_txn *txn);
 static MDB_page *mdbenv_get_page(MDB_env *env, pgno_t pgno);
 
@@ -473,7 +472,7 @@ int
 mdb_txn_begin(MDB_env *env, int rdonly, MDB_txn **ret)
 {
        MDB_txn *txn;
-       int rc;
+       int rc, toggle;
 
        if ((txn = calloc(1, sizeof(*txn))) == NULL) {
                DPRINTF("calloc: %s", strerror(errno));
@@ -504,7 +503,7 @@ mdb_txn_begin(MDB_env *env, int rdonly, MDB_txn **ret)
        if (rdonly) {
                MDB_reader *r = pthread_getspecific(env->me_txkey);
                if (!r) {
-                       int i;
+                       unsigned int i;
                        pthread_mutex_lock(&env->me_txns->mt_mutex);
                        for (i=0; i<env->me_maxreaders; i++) {
                                if (env->me_txns->mt_readers[i].mr_pid == 0) {
@@ -529,11 +528,14 @@ mdb_txn_begin(MDB_env *env, int rdonly, MDB_txn **ret)
 
        txn->mt_env = env;
 
-       if ((rc = mdbenv_read_meta(env)) != MDB_SUCCESS) {
+       if ((rc = mdbenv_read_meta(env, &toggle)) != MDB_SUCCESS) {
                mdb_txn_abort(txn);
                return rc;
        }
 
+       if (toggle)
+               txn->mt_flags |= MDB_TXN_METOGGLE;
+
        txn->mt_next_pgno = env->me_meta.mm_last_pg+1;
        txn->mt_root = env->me_meta.mm_root;
        DPRINTF("begin transaction %lu on mdbenv %p, root page %lu",
@@ -839,7 +841,7 @@ mdbenv_write_meta(MDB_txn *txn)
        meta.mm_txnid = txn->mt_txnid;
 
        off = 0;
-       if (!env->me_metatoggle)
+       if (!F_ISSET(txn->mt_flags, MDB_TXN_METOGGLE))
                off = env->me_meta.mm_stat.ms_psize;
        off += PAGEHDRSZ;
 
@@ -867,7 +869,7 @@ mdb_check_meta_page(MDB_page *p)
 }
 
 static int
-mdbenv_read_meta(MDB_env *env)
+mdbenv_read_meta(MDB_env *env, int *which)
 {
        MDB_page        *mp0, *mp1;
        MDB_meta        *meta[2];
@@ -893,7 +895,8 @@ mdbenv_read_meta(MDB_env *env)
 
        if (meta[toggle]->mm_txnid > env->me_meta.mm_txnid) {
                bcopy(meta[toggle], &env->me_meta, sizeof(env->me_meta));
-               env->me_metatoggle = toggle;
+               if (which)
+                       *which = toggle;
        }
 
        DPRINTF("Using meta page %d", toggle);
@@ -912,6 +915,8 @@ mdbenv_create(MDB_env **env)
        e->me_meta.mm_mapsize = DEFAULT_MAPSIZE;
        e->me_maxreaders = DEFAULT_READERS;
        e->me_db.md_env = e;
+       e->me_fd = -1;
+       e->me_lfd = -1;
        *env = e;
        return MDB_SUCCESS;
 }
@@ -977,7 +982,7 @@ mdbenv_open2(MDB_env *env, unsigned int flags)
                }
        }
 
-       if ((i = mdbenv_read_meta(env)) != 0)
+       if ((i = mdbenv_read_meta(env, NULL)) != 0)
                return i;
 
        DPRINTF("opened database version %u, pagesize %u",
@@ -1002,51 +1007,131 @@ mdbenv_reader_dest(void *ptr)
        reader->mr_tid = 0;
 }
 
-int
-mdbenv_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode)
+static void
+mdbenv_share_locks(MDB_env *env)
 {
-       int             oflags, rc, shmid;
-       off_t   size;
+       struct flock lock_info;
 
+       env->me_txns->mt_txnid = env->me_meta.mm_txnid;
 
-       if (F_ISSET(flags, MDB_RDONLY))
-               oflags = O_RDONLY;
-       else
-               oflags = O_RDWR | O_CREAT;
+       memset((void *)&lock_info, 0, sizeof(lock_info));
+       lock_info.l_type = F_RDLCK;
+       lock_info.l_whence = SEEK_SET;
+       lock_info.l_start = 0;
+       lock_info.l_len = 1;
+       fcntl(env->me_lfd, F_SETLK, &lock_info);
+}
 
-       if ((env->me_fd = open(path, oflags, mode)) == -1)
-               return errno;
+static int
+mdbenv_setup_locks(MDB_env *env, char *lpath, int mode, int *excl)
+{
+       int rc;
+       off_t size, rsize;
+       struct flock lock_info;
 
-       env->me_shmkey = ftok(path, 'm');
-       size = (env->me_maxreaders-1) * sizeof(MDB_reader) + sizeof(MDB_txninfo);
-       shmid = shmget(env->me_shmkey, size, IPC_CREAT|IPC_EXCL|mode);
-       if (shmid == -1) {
-               if (errno == EEXIST) {
-                       shmid = shmget(env->me_shmkey, size, IPC_CREAT|mode);
-                       if (shmid == -1)
-                               return errno;
-                       env->me_txns = shmat(shmid, NULL, 0);
-                       if (env->me_txns->mt_magic != MDB_MAGIC ||
-                               env->me_txns->mt_version != MDB_VERSION) {
-                                       DPRINTF("invalid lock region %d", shmid);
-                                       shmdt(env->me_txns);
-                                       env->me_txns = NULL;
-                                       return EIO;
-                               }
-               } else {
-                       return errno;
+       *excl = 0;
+
+       if ((env->me_lfd = open(lpath, O_RDWR|O_CREAT, mode)) == -1) {
+               rc = errno;
+               return rc;
+       }
+       /* Try to get exclusive lock. If we succeed, then
+        * nobody is using the lock region and we should initialize it.
+        */
+       memset((void *)&lock_info, 0, sizeof(lock_info));
+       lock_info.l_type = F_WRLCK;
+       lock_info.l_whence = SEEK_SET;
+       lock_info.l_start = 0;
+       lock_info.l_len = 1;
+       rc = fcntl(env->me_lfd, F_SETLK, &lock_info);
+       if (rc == 0) {
+               *excl = 1;
+       } else {
+               lock_info.l_type = F_RDLCK;
+               rc = fcntl(env->me_lfd, F_SETLK, &lock_info);
+               if (rc) {
+                       rc = errno;
+                       goto fail;
+               }
+       }
+       size = lseek(env->me_lfd, 0, SEEK_END);
+       rsize = (env->me_maxreaders-1) * sizeof(MDB_reader) + sizeof(MDB_txninfo);
+       if (size < rsize && *excl) {
+               if (ftruncate(env->me_lfd, rsize) != 0) {
+                       rc = errno;
+                       goto fail;
                }
        } else {
+               rsize = size;
+               size = rsize - sizeof(MDB_txninfo);
+               env->me_maxreaders = size/sizeof(MDB_reader) + 1;
+       }
+       env->me_txns = mmap(0, rsize, PROT_READ|PROT_WRITE, MAP_SHARED,
+               env->me_lfd, 0);
+       if (env->me_txns == MAP_FAILED) {
+               rc = errno;
+               goto fail;
+       }
+       if (*excl) {
                pthread_mutexattr_t mattr;
 
-               env->me_txns = shmat(shmid, NULL, 0);
                pthread_mutexattr_init(&mattr);
                pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
                pthread_mutex_init(&env->me_txns->mt_mutex, &mattr);
                pthread_mutex_init(&env->me_txns->mt_wmutex, &mattr);
                env->me_txns->mt_version = MDB_VERSION;
                env->me_txns->mt_magic = MDB_MAGIC;
+               env->me_txns->mt_txnid = 0;
+               env->me_txns->mt_numreaders = 0;
+
+       } else {
+               if (env->me_txns->mt_magic != MDB_MAGIC) {
+                       DPRINTF("lock region has invalid magic");
+                       errno = EINVAL;
+               }
+               if (env->me_txns->mt_version != MDB_VERSION) {
+                       DPRINTF("lock region is version %u, expected version %u",
+                               env->me_txns->mt_version, MDB_VERSION);
+                       errno = EINVAL;
+               }
+               if (errno != EACCES && errno != EAGAIN) {
+                       rc = errno;
+                       goto fail;
+               }
        }
+       return MDB_SUCCESS;
+
+fail:
+       close(env->me_lfd);
+       return rc;
+
+}
+
+int
+mdbenv_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode)
+{
+       int             oflags, rc, len, excl;
+       char *lpath, *dpath;
+
+       len = strlen(path);
+       lpath = malloc(len + sizeof("/lock.mdb") + len + sizeof("/data.db"));
+       if (!lpath)
+               return ENOMEM;
+       dpath = lpath + len + sizeof("/lock.mdb");
+       sprintf(lpath, "%s/lock.mdb", path);
+       sprintf(dpath, "%s/data.mdb", path);
+
+       rc = mdbenv_setup_locks(env, lpath, mode, &excl);
+       if (rc)
+               goto leave;
+
+       if (F_ISSET(flags, MDB_RDONLY))
+               oflags = O_RDONLY;
+       else
+               oflags = O_RDWR | O_CREAT;
+
+       if ((env->me_fd = open(dpath, oflags, mode)) == -1)
+               return errno;
 
        if ((rc = mdbenv_open2(env, flags)) != MDB_SUCCESS) {
                close(env->me_fd);
@@ -1054,10 +1139,14 @@ mdbenv_open(MDB_env *env, const char *path, unsigned int flags, mode_t mode)
        } else {
                env->me_path = strdup(path);
                DPRINTF("opened dbenv %p", (void *) env);
+               pthread_key_create(&env->me_txkey, mdbenv_reader_dest);
+               if (excl)
+                       mdbenv_share_locks(env);
        }
 
-       pthread_key_create(&env->me_txkey, mdbenv_reader_dest);
 
+leave:
+       free(lpath);
        return rc;
 }
 
@@ -1074,8 +1163,10 @@ mdbenv_close(MDB_env *env)
        }
        close(env->me_fd);
        if (env->me_txns) {
-               shmdt(env->me_txns);
+               size_t size = (env->me_maxreaders-1) * sizeof(MDB_reader) + sizeof(MDB_txninfo);
+               munmap(env->me_txns, size);
        }
+       close(env->me_lfd);
        free(env);
 }
 
@@ -1295,7 +1386,7 @@ mdb_search_page(MDB_db *db, MDB_txn *txn, MDB_val *key,
         * committed root page.
         */
        if (txn == NULL) {
-               if ((rc = mdbenv_read_meta(db->md_env)) != MDB_SUCCESS)
+               if ((rc = mdbenv_read_meta(db->md_env, NULL)) != MDB_SUCCESS)
                        return rc;
                root = db->md_env->me_meta.mm_root;
        } else if (F_ISSET(txn->mt_flags, MDB_TXN_ERROR)) {