libmount: clean up lock.c

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 62 insertions, 52 deletions

diff --git a/shlibs/mount/src/lock.c b/shlibs/mount/src/lock.c
index 0f35aa3bd..beea23980 100644
--- a/shlibs/mount/src/lock.c
+++ b/shlibs/mount/src/lock.c
@@ -36,7 +36,6 @@
  * lock handler
  */
 struct _mnt_lock {
-	pid_t	id;		/* getpid() or so (see linkfile)... */
 	char	*lockfile;	/* path to lock file (e.g. /etc/mtab~) */
 	char	*linkfile;	/* path to link file (e.g. /etc/mtab~.<id>) */
 	int	lockfile_fd;	/* lock file descriptor */
@@ -46,30 +45,44 @@ struct _mnt_lock {
 
 /**
  * mnt_new_lock:
- * @lockfile: path to lockfile or NULL (default is _PATH_MOUNTED_LOCK)
+ * @dataname: the file that should be covered by the lock
  * @id: unique linkfile identifier or 0 (default is getpid())
  *
  * Returns: newly allocated lock handler or NULL on case of error.
  */
-mnt_lock *mnt_new_lock(const char *lockfile, pid_t id)
+mnt_lock *mnt_new_lock(const char *datafile, pid_t id)
 {
-	mnt_lock *ml = calloc(1, sizeof(struct _mnt_lock));
+	mnt_lock *ml = NULL;
+	char *lo = NULL, *ln = NULL;
 
-	if (!ml)
+	/* lockfile */
+	if (!datafile)
 		return NULL;
 
-	ml->lockfile_fd = -1;
-	ml->id = id;
-	if (lockfile) {
-		ml->lockfile = strdup(lockfile);
-		if (!ml->lockfile) {
-			free(ml);
-			return NULL;
-		}
+	if (asprintf(&lo, "%s~", datafile) == -1) {
+		lo = NULL;
+		goto err;
+	}
+	if (asprintf(&ln, "%s~.%d", datafile, id ? : getpid()) == -1) {
+		ln = NULL;
+		goto err;
 	}
+	ml = calloc(1, sizeof(struct _mnt_lock) );
+	if (!ml)
+		goto err;
+
+	ml->lockfile_fd = -1;
+	ml->linkfile = ln;
+	ml->lockfile = lo;
 	return ml;
+err:
+	free(lo);
+	free(ln);
+	free(ml);
+	return NULL;
 }
 
+
 /**
  * mnt_free_lock:
  * @ml: mnt_lock handler
@@ -93,38 +106,21 @@ void mnt_free_lock(mnt_lock *ml)
  */
 const char *mnt_lock_get_lockfile(mnt_lock *ml)
 {
-	if (!ml)
-		return NULL;
-	if (ml->lockfile)
-		return ml->lockfile;
-	return _PATH_MOUNTED_LOCK;
+	return ml ? ml->lockfile : NULL;
 }
 
 /**
  * mnt_lock_get_linkfile:
  * @ml: mnt_lock handler
  *
- * Returns: unique (per process) path to linkfile.
+ * Note that the filename is generated by mnt_new_lock() and depends on
+ * getpid() or 'id' argument of the mnt_new_lock() function.
+ *
+ * Returns: unique (per process/thread) path to linkfile.
  */
 const char *mnt_lock_get_linkfile(mnt_lock *ml)
 {
-	if (!ml)
-		return NULL;
-
-	if (!ml->linkfile) {
-		const char *lf = mnt_lock_get_lockfile(ml);
-		size_t sz;
-
-		if (!lf)
-			return NULL;
-		sz = strlen(lf) + 32;
-
-		ml->linkfile = malloc(sz);
-		if (ml->linkfile)
-			snprintf(ml->linkfile, sz, "%s.%d",
-					lf, ml->id ? ml->id : getpid());
-	}
-	return ml->linkfile;
+	return ml ? ml->linkfile : NULL;
 }
 
 static void mnt_lockalrm_handler(int sig)
@@ -208,8 +204,10 @@ static int mnt_wait_lock(mnt_lock *ml, struct flock *fl, time_t maxtime)
  *
  * This mtab locking code has been refactored and moved to libmount. The mtab
  * locking is really not perfect (e.g. SIGALRM), but it's stable, reliable and
- * backwardly compatible code. Don't forget that this code has to be compatible
- * with 3rd party mounts (/sbin/mount.<foo>) and has to work with NFS.
+ * backwardly compatible code.
+ *
+ * Don't forget that this code has to be compatible with 3rd party mounts
+ * (/sbin/mount.<foo>) and has to work with NFS.
  * -- kzak@redhat.com [May-2009]
  */
 
@@ -219,13 +217,20 @@ static int mnt_wait_lock(mnt_lock *ml, struct flock *fl, time_t maxtime)
 /* sleep time (in microseconds, max=999999) between attempts */
 #define MOUNTLOCK_WAITTIME		5000
 
-/* Remove lock file.  */
+/**
+ * mnt_unlock_file:
+ * @ml: lock struct
+ *
+ * Unlocks the file. The function could be called independently on the
+ * lock status (for example from exit(3)).
+ */
 void mnt_unlock_file(mnt_lock *ml)
 {
 	if (!ml)
 		return;
 
-	DBG(DEBUG_LOCKS, fprintf(stderr, "LOCK: (%d) unlocking/cleaning.\n", getpid()));
+	DBG(DEBUG_LOCKS, fprintf(stderr,
+			"LOCK: (%d) unlocking/cleaning.\n", getpid()));
 
 	if (ml->locked == 0 && ml->lockfile && ml->linkfile)
 	{
@@ -286,10 +291,14 @@ void mnt_unlock_file(mnt_lock *ml)
  *	int update_mtab()
  *	{
  *		int sig = 0;
+ *		const char *mtab;
  *
- *		atexit(unlock_fallback);
+ *		if (!(mtab = mnt_get_writable_mtab_path()))
+ *			return 0;			// system without mtab
+ *		if (!(ml = mnt_new_lock(mtab, 0)))
+ *			return -1;			// error
  *
- *		ml = mnt_new_lock(NULL, 0);
+ *		atexit(unlock_fallback);
  *
  *		if (mnt_lock_file(ml) != 0) {
  *			printf(stderr, "cannot create %s lockfile\n",
@@ -404,7 +413,7 @@ int mnt_lock_file(mnt_lock *ml)
 	}
 	DBG(DEBUG_LOCKS, fprintf(stderr,
 			"LOCK: %s: (%d) successfully locked\n",
-			ml->lockfile, getpid()));
+			lockfile, getpid()));
 	unlink(linkfile);
 	return 0;
 
@@ -464,15 +473,14 @@ void sig_handler(int sig)
 
 int test_lock(struct mtest *ts, int argc, char *argv[])
 {
-	const char *lockfile, *datafile;
+	const char *datafile;
 	int verbose = 0, loops, l;
 
-	if (argc < 4)
+	if (argc < 3)
 		return -1;
 
-	lockfile = argv[1];
-	datafile = argv[2];
-	loops = atoi(argv[3]);
+	datafile = argv[1];
+	loops = atoi(argv[2]);
 
 	if (argc == 5 && strcmp(argv[4], "--verbose") == 0)
 		verbose = 1;
@@ -493,11 +501,13 @@ int test_lock(struct mtest *ts, int argc, char *argv[])
 	}
 
 	for (l = 0; l < loops; l++) {
-		lock = mnt_new_lock(lockfile, 0);
+		lock = mnt_new_lock(datafile, 0);
+		if (!lock)
+			return -1;
 
 		if (mnt_lock_file(lock) == -1) {
-			fprintf(stderr, "%d: failed to create lock file: %s\n",
-					getpid(), lockfile);
+			fprintf(stderr, "%d: failed to lock %s file\n",
+					getpid(), datafile);
 			return -1;
 		}
 
@@ -518,7 +528,7 @@ int test_lock(struct mtest *ts, int argc, char *argv[])
 int main(int argc, char *argv[])
 {
 	struct mtest tss[] = {
-	{ "--lock", test_lock,  "  <lockfile> <datafile> <loops> [--verbose]   increment number in datafile" },
+	{ "--lock", test_lock,  "  <datafile> <loops> [--verbose]   increment number in datafile" },
 	{ NULL }
 	};