Reliable db locking

[netatalk.git] / etc / cnid_dbd / main.c

diff --git a/etc/cnid_dbd/main.c b/etc/cnid_dbd/main.c
index febadc1a7cae04d7c1daeae7299e7f300616ffe5..bf71b72d5945e8a63772d2da4639e3c204490197 100644 (file)
--- a/etc/cnid_dbd/main.c
+++ b/etc/cnid_dbd/main.c
@@ -1,5 +1,5 @@
 /*
- * $Id: main.c,v 1.15 2009-10-19 08:09:07 didg Exp $
+ * $Id: main.c,v 1.16 2009-11-25 14:59:15 franklahm Exp $
  *
  * Copyright (C) Joerg Lenneis 2003
  * Copyright (c) Frank Lahm 2009
@@ -34,23 +34,22 @@
 #include <netatalk/endian.h>
 #include <atalk/cnid_dbd_private.h>
 #include <atalk/logger.h>
+#include <atalk/util.h>
 
 #include "db_param.h"
 #include "dbif.h"
 #include "dbd.h"
 #include "comm.h"
 
-#define LOCKFILENAME  "lock"
-
 /* 
    Note: DB_INIT_LOCK is here so we can run the db_* utilities while netatalk is running.
    It's a likey performance hit, but it might we worth it.
  */
-#define DBOPTIONS (DB_CREATE | DB_INIT_LOG | DB_INIT_MPOOL | DB_INIT_LOCK | DB_INIT_TXN | DB_RECOVER)
+#define DBOPTIONS (DB_CREATE | DB_INIT_LOG | DB_INIT_MPOOL | DB_INIT_LOCK | DB_INIT_TXN)
 
 static DBD *dbd;
-
 static int exit_sig = 0;
+static int db_locked;
 
 static void sig_exit(int signo)
 {
@@ -153,7 +152,7 @@ static int loop(struct db_param *dbp)
                 ret = 1;
                 break;
             case CNID_DBD_OP_ADD:
-                ret = dbd_add(dbd, &rqst, &rply);
+                ret = dbd_add(dbd, &rqst, &rply, 0);
                 break;
             case CNID_DBD_OP_GET:
                 ret = dbd_get(dbd, &rqst, &rply);
@@ -162,7 +161,7 @@ static int loop(struct db_param *dbp)
                 ret = dbd_resolve(dbd, &rqst, &rply);
                 break;
             case CNID_DBD_OP_LOOKUP:
-                ret = dbd_lookup(dbd, &rqst, &rply);
+                ret = dbd_lookup(dbd, &rqst, &rply, 0);
                 break;
             case CNID_DBD_OP_UPDATE:
                 ret = dbd_update(dbd, &rqst, &rply);
@@ -252,33 +251,6 @@ static void switch_to_user(char *dir)
     }
 }
 
-/* ------------------------ */
-static int get_lock(void)
-{
-    int lockfd;
-    struct flock lock;
-
-    if ((lockfd = open(LOCKFILENAME, O_RDWR | O_CREAT, 0644)) < 0) {
-        LOG(log_error, logtype_cnid, "main: error opening lockfile: %s", strerror(errno));
-        exit(1);
-    }
-
-    lock.l_start  = 0;
-    lock.l_whence = SEEK_SET;
-    lock.l_len    = 0;
-    lock.l_type   = F_WRLCK;
-
-    if (fcntl(lockfd, F_SETLK, &lock) < 0) {
-        if (errno == EACCES || errno == EAGAIN) {
-            exit(0);
-        } else {
-            LOG(log_error, logtype_cnid, "main: fcntl F_WRLCK lockfile: %s", strerror(errno));
-            exit(1);
-        }
-    }
-
-    return lockfd;
-}
 
 /* ----------------------- */
 static void set_signal(void)
@@ -302,25 +274,12 @@ static void set_signal(void)
     }
 }
 
-/* ----------------------- */
-static void free_lock(int lockfd)
-{
-    struct flock lock;
-
-    lock.l_start  = 0;
-    lock.l_whence = SEEK_SET;
-    lock.l_len    = 0;
-    lock.l_type = F_UNLCK;
-    fcntl(lockfd, F_SETLK, &lock);
-    close(lockfd);
-}
-
 /* ------------------------ */
 int main(int argc, char *argv[])
 {
     struct db_param *dbp;
     int err = 0;
-    int lockfd, ctrlfd, clntfd;
+    int ctrlfd, clntfd;
     char *dir, *logconfig;
 
     set_processname("cnid_dbd");
@@ -339,9 +298,18 @@ int main(int argc, char *argv[])
 
     switch_to_user(dir);
 
-    /* Before we do anything else, check if there is an instance of cnid_dbd
-       running already and silently exit if yes. */
-    lockfd = get_lock();
+    /* Get db lock */
+    if ((db_locked = get_lock(LOCK_EXCL, dir)) == -1) {
+        LOG(log_error, logtype_cnid, "main: fatal db lock error");
+        exit(1);
+    }
+    if (db_locked != LOCK_EXCL) {
+        /* Couldn't get exclusive lock, try shared lock  */
+        if ((db_locked = get_lock(LOCK_SHRD, NULL)) != LOCK_SHRD) {
+            LOG(log_error, logtype_cnid, "main: fatal db lock error");
+            exit(1);
+        }
+    }
 
     LOG(log_info, logtype_cnid, "Startup, DB dir %s", dir);
 
@@ -357,7 +325,10 @@ int main(int argc, char *argv[])
     if (NULL == (dbd = dbif_init(".", "cnid2.db")))
         exit(2);
 
-    if (dbif_env_open(dbd, dbp, DBOPTIONS) < 0)
+    /* Only recover if we got the lock */
+    if (dbif_env_open(dbd,
+                      dbp,
+                      (db_locked == LOCK_EXCL) ? DBOPTIONS | DB_RECOVER : DBOPTIONS) < 0)
         exit(2); /* FIXME: same exit code as failure for dbif_open() */
     LOG(log_debug, logtype_cnid, "Finished initializing BerkeleyDB environment");
 
@@ -367,6 +338,19 @@ int main(int argc, char *argv[])
     }
     LOG(log_debug, logtype_cnid, "Finished opening BerkeleyDB databases");
 
+    /* Downgrade db lock  */
+    if (db_locked == LOCK_EXCL) {
+        if (get_lock(LOCK_UNLOCK, NULL) != 0) {
+            dbif_close(dbd);
+            exit(2);
+        }
+        if (get_lock(LOCK_SHRD, NULL) != LOCK_SHRD) {
+            dbif_close(dbd);
+            exit(2);
+        }
+    }
+
+
     if (dbd_stamp(dbd) < 0) {
         dbif_close(dbd);
         exit(5);
@@ -387,8 +371,6 @@ int main(int argc, char *argv[])
     if (dbif_prep_upgrade(dir) < 0)
         err++;
 
-    free_lock(lockfd);
-
     if (err)
         exit(4);
     else if (exit_sig)