improved statfs (symlink handling, handling of default PGDATA)

4 files changed, 71 insertions, 11 deletions

diff --git a/DEVELOPERS b/DEVELOPERS
index fc329ea..d146bb5 100644
--- a/DEVELOPERS
+++ b/DEVELOPERS
@@ -140,7 +140,7 @@ Calculate the size of:
 a) virtual things like blocks and inodes (that's the way we went)
 b) get physical disk usage data from the database directly
 
-b) Detect location of tables on disk
+B) Detect location of tables on disk
 
 a) environment variable PGDATA
    Is only really set for the postgresql startup script and for the
@@ -153,7 +153,9 @@ b) standard location (probed)
    /var/lib/postgres/data
    ERROR:  must be superuser to examine "data_directory"
    Can't do this, as the db user must be underprivileged:
-c) When the DBA create dedicated tablespaces, then there is no problem
+   ArchLinux: /var/lib/postgres
+   Centos/RHEL/Fedora: /var/lib/pgsql
+   Debian/Ubuntu: /var/lib/postgresql/9.1/main (/var/lib/postgresql should be fine)
     
 This is a rough sketch of the algorithm:
 
diff --git a/TODO b/TODO
index bff7c24..45de361 100644
--- a/TODO
+++ b/TODO
@@ -1,8 +1,10 @@
 TODO list (in order of priority)
 ---------
 
-- integrate statfs patch:
-  - no Perl, Shell, Posix df dependency
+- integrate statfs patch
+  - find alteratives way to determine PGDATA at runtime (by NOT
+    asking the Postgresql server)
+  - find a way to calculate PGDATA while compiling
 - handling of most file system metadata
   - ownership: how is this done depending on
     per-user or root mounts? think about security
diff --git a/pgfuse.c b/pgfuse.c
index b74af59..5593839 100644
--- a/pgfuse.c
+++ b/pgfuse.c
@@ -30,6 +30,7 @@
 #include <inttypes.h>		/* for PRIxxx macros */
 #include <mntent.h>		/* for iterating mount entries */
 #include <sys/vfs.h>		/* for statfs */
+#include <limits.h>
 
 #include <fuse.h>		/* for user-land filesystem */
 #include <fuse_opt.h>		/* fuse command line parser */
@@ -968,6 +969,20 @@ static int pgfuse_statfs( const char *path, struct statvfs *buf )
 		return res;
 	}
 
+	/* transform them and especially resolve symlinks */
+	for( i = 0; i < nof_locations; i++ ) {
+		char *old_path = location[i];
+		char *new_path = realpath( old_path, NULL );
+		if( new_path == NULL ) {
+			/* do nothing, most likely a permission problem */
+			syslog( LOG_ERR, "realpath for '%s' failed: %s,  pgfuse mount point '%s', thread #%u",
+				old_path, strerror( errno ), data->mountpoint, THREAD_ID );
+		} else {
+			location[i] = new_path;
+			free( old_path );
+		}
+	}
+	
 	blocks_free = INT64_MAX;
 	blocks_avail = INT64_MAX;
 	
diff --git a/pgsql.c b/pgsql.c
index 4a2e776..0022603 100644
--- a/pgsql.c
+++ b/pgsql.c
@@ -984,6 +984,48 @@ static int get_default_tablespace( PGconn *conn, int verbose )
 	return oid;
 }
 
+static char *get_data_directory( PGconn *conn )
+{
+	PGresult *res;
+	char *data;
+
+	/* in the questionable case we have super user rights we
+	 * can ask the server for the default path */
+	res = PQexec( conn, "select setting from pg_settings where name = 'data_directory'" );
+	
+	if( PQresultStatus( res ) != PGRES_TUPLES_OK ) {
+		syslog( LOG_ERR, "Error getting data_directory: %s", PQerrorMessage( conn ) );
+		PQclear( res );
+		return NULL;
+	}
+
+	/* No permissions results in an empty result set */
+	if( PQntuples( res ) == 0 ) {
+		PQclear( res );
+
+		/* No location, tablespace resides in PGDATA,
+		 * usually it lies in /var/lib/postgres, 
+		 * /var/lib/postgresql,
+		 * /var/lib/pgsql or  /var/lib/postgresql/9.1/main
+		 */
+#ifdef __linux__
+		data = strdup( "/var/lib/postgres" );
+#else
+		/* TODO, but usually BSD stores it on /usr/local, MacOs
+		 * would be different, but there a lot else is also different..
+		 */
+		data = strdup( "/usr/local" );
+#endif
+		return data;
+	}
+
+	data = strdup( PQgetvalue( res, 0, 0 ) );
+
+	PQclear( res );
+	
+	return data;
+}
+
 static char *get_tablespace_location( PGconn *conn, const int oid, int verbose )
 {
 	PGresult *res;
@@ -1012,6 +1054,12 @@ static char *get_tablespace_location( PGconn *conn, const int oid, int verbose )
 	data = strdup( PQgetvalue( res, 0, 0 ) );
 
 	PQclear( res );
+
+	/* no direct information in the catalog about the table space location, try
+	 * other means */
+	if( strcmp( data, "" ) == 0 ) {
+		data = get_data_directory( conn );
+	}
 	
 	return data;
 }
@@ -1078,13 +1126,6 @@ int psql_get_tablespace_locations( PGconn *conn, char **location, size_t *nof_oi
 		location[i] = get_tablespace_location( conn, oid[i], verbose );
 	}
 
-	/* TODO: */
-	for( i = 0; i < *nof_oids; i++ ) {
-		if( !location[i] ) {
-			/* No location, tablespace resides in PGDATA */
-		}
-	}
-
 	for( i = 0; i < *nof_oids; i++ ) {
 		if( verbose ) {
 			syslog( LOG_DEBUG, "Free blocks calculation, seen tablespace OID %d, %s",