Re-implement database locking for Berkeley DB

git-svn-id: file:///svnroot/mailfromd/trunk@1352 7a8a7f39-df28-0410-adc6-e0d955640f24

2 files changed, 127 insertions, 19 deletions

diff --git a/ChangeLog b/ChangeLog
index 177e1fb5..75150bbb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2007-04-12  Sergey Poznyakoff  <gray@gnu.org.ua>
 
+	* src/mu_dbm.c: Re-implement database locking for Berkeley DB
+
         * src/mu_dbm.c, src/mu_dbm.h (mu_dbm_strerror): New function
         (mu_dbm_firstkey, mu_dbm_nextkey): Change signature
 	* src/dnscache.c, src/db.c, src/cache.c, src/rate.c,
diff --git a/src/mu_dbm.c b/src/mu_dbm.c
index 421a846c..461731e7 100644
--- a/src/mu_dbm.c
+++ b/src/mu_dbm.c
@@ -46,15 +46,12 @@ mu_fcheck_perm (int fd, int mode)
   if (fstat (fd, &st) == -1)
     {
       if (errno == ENOENT)
-	return 0;
+	return ENOENT;
       else
-	return 1;
+	return MU_ERR_FAILURE;
     }
   if ((st.st_mode & 0777) != mode)
-    {
-      errno = MU_ERR_UNSAFE_PERMS;
-      return 1;
-    }
+    return errno = MU_ERR_UNSAFE_PERMS;
   return 0;
 }
 
@@ -68,25 +65,18 @@ mu_check_perm (const char *name, int mode)
   if (stat (name, &st) == -1)
     {
       if (errno == ENOENT)
-	return 0;
+	return ENOENT;
       else
-	return 1;
+	return MU_ERR_FAILURE;
     }
   if ((st.st_mode & 0777) != mode)
-    {
-      errno = MU_ERR_UNSAFE_PERMS;
-      return 1;
-    }
+    return errno = MU_ERR_UNSAFE_PERMS;
+
   return 0;
 }
 
 #if defined(WITH_GDBM)
 
-void
-mu_dbm_finish ()
-{
-}
-
 int
 mu_dbm_open (char *name, DBM_FILE *db, int flags, int mode, int *ro)
 {
@@ -216,6 +206,8 @@ mu_dbm_datum_free (DBM_DATUM *datum)
 const char *
 mu_dbm_strerror ()
 {
+  if (errno == MU_ERR_UNSAFE_PERMS)
+    return mu_strerror (errno);
   return gdbm_strerror (gdbm_errno);
 }
 
@@ -223,6 +215,68 @@ mu_dbm_strerror ()
 
 int mu_dbm_errno;
 
+static int
+lock_file (int fd, int type)
+{
+  int i;
+  struct flock fl;
+  int rc = 0;
+
+  memset(&fl, 0, sizeof fl);
+  fl.l_whence = SEEK_SET;
+  fl.l_type = type;
+
+  for (i = 0; i < lock_retry_count_option; i++)
+    {
+      if (fcntl(fd, F_SETLK, &fl) == 0) 
+        {
+          rc = 0;
+          break;
+        }
+      rc = errno;
+      if (!(errno == EAGAIN || errno == EACCES))
+	break;
+      sleep (lock_retry_timeout_option);
+    }
+  return rc;
+}
+
+#define LOCK_SUFFIX ".lock"
+
+static int
+make_lockfile (char *name, int *pfd, char **plockname)
+{
+  int rc;
+  int fd;
+  char *lockname;
+  size_t size;
+
+  size = strlen (name) + sizeof LOCK_SUFFIX;
+  lockname = malloc (size);
+  if (!lockname)
+    return errno;
+  strcpy (lockname, name);
+  strcat (lockname, LOCK_SUFFIX);
+  fd = open (lockname, O_CREAT|O_RDWR, 0600);
+  if (!fd)
+    {
+      free (lockname);
+      return errno;
+    }
+
+  rc = lock_file (fd, F_WRLCK);
+  if (rc)
+    {
+      free (lockname);
+      return rc;
+    }
+
+  *plockname = lockname;
+  *pfd = fd;
+  return 0;
+}
+      
+
 static void
 mu_dbm_errcall_fcn (const char *errpfx, char *msg)
 {
@@ -235,10 +289,14 @@ mu_dbm_errcall_fcn (const char *errpfx, char *msg)
 int
 mu_dbm_open (char *name, DBM_FILE *dbm, int flags, int mode, int *ro)
 {
-  int f, rc;
+  int f;
   DB *db = NULL;
+  int lockfd = -1;
+  char *lockname;
+  int fd;
   
-  if (mu_check_perm (name, mode))
+  mu_dbm_errno = mu_check_perm (name, mode);
+  if (mu_dbm_errno && mu_dbm_errno != ENOENT)
     return MU_ERR_UNSAFE_PERMS;
 
   if (ro)
@@ -251,6 +309,8 @@ mu_dbm_open (char *name, DBM_FILE *dbm, int flags, int mode, int *ro)
       break;
       
     case MU_STREAM_READ:
+      if (mu_dbm_errno == ENOENT)
+	return MU_ERR_FAILURE;
       f = DB_RDONLY;
       break;
       
@@ -263,6 +323,17 @@ mu_dbm_open (char *name, DBM_FILE *dbm, int flags, int mode, int *ro)
       return -1;
    }
 
+  if (mu_dbm_errno == ENOENT)
+    {
+      mu_dbm_errno = make_lockfile (name, &lockfd, &lockname);
+      if (mu_dbm_errno)
+	{
+	  mu_error ("Cannot lock file %s: %s",
+		    name, mu_strerror (mu_dbm_errno));
+	  return MU_ERR_FAILURE;
+	}
+    }
+  
 #if DB_VERSION_MAJOR == 2
   mu_dbm_errno = db_open (name, DB_HASH, f, mode, NULL, NULL, &db);
 #else
@@ -277,10 +348,39 @@ mu_dbm_open (char *name, DBM_FILE *dbm, int flags, int mode, int *ro)
 #endif
   if (mu_dbm_errno)
     return MU_ERR_FAILURE;
+
+  if (mu_dbm_errno = db->fd (db, &fd))
+    {
+      mu_error("Cannot get file descriptor for the database: %s",
+	       mu_dbm_strerror ());
+      db->close (db, 0);
+      if (lockfd != -1)
+	{
+	  unlink (lockname);
+	  free (lockname);
+	  close (lockfd);
+	}
+      return MU_ERR_FAILURE;
+    }
+
+  mu_dbm_errno = lock_file (fd, (flags == MU_STREAM_READ) ? F_RDLCK : F_WRLCK);
+  if (lockfd != -1)
+    {
+      unlink (lockname);
+      free (lockname);
+      close (lockfd);
+    }
+  
+  if (mu_dbm_errno)
+    {
+      db->close (db, 0);
+      return MU_ERR_FAILURE;
+    }
   
   dbm->name = strdup (name);
   dbm->db = db;
   dbm->dbc = NULL;
+
   return 0;
 }
 
@@ -413,7 +513,13 @@ mu_dbm_datum_free(DBM_DATUM *datum)
 const char *
 mu_dbm_strerror ()
 {
+  if (errno == MU_ERR_UNSAFE_PERMS)
+    return mu_strerror (errno);
+#if DB_VERSION_MAJOR > 2
   return db_strerror (mu_dbm_errno);
+#else
+  return mu_strerror (mu_dbm_errno);
+#endif
 }
 
 #endif