[PATCH v2 07/25] lock_file(): always add lock_file object to lock_file_list

[Michael Haggerty <mhagger@alum.mit.edu>]

It used to be that if locking failed, lock_file() usually did not
register the lock_file object in lock_file_list but sometimes it did.
This confusion was compounded if lock_file() was called via
hold_lock_file_for_append(), which has its own failure modes.

The ambiguity didn't have any ill effects, because lock_file objects
cannot be removed from the lock_file_list anyway.  But it is
unnecessary to leave this behavior inconsistent.

So change lock_file() to *always* ensure that the lock_file object is
registered in lock_file_list regardless of whether an error occurs.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 lockfile.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/lockfile.c b/lockfile.c
index e78a35f..120a6d6 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -130,6 +130,22 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 	 */
 	static const size_t max_path_len = sizeof(lk->filename) - 5;
 
+	if (!lock_file_list) {
+		/* One-time initialization */
+		sigchain_push_common(remove_lock_file_on_signal);
+		atexit(remove_lock_file);
+	}
+
+	if (!lk->on_list) {
+		/* Initialize *lk and add it to lock_file_list: */
+		lk->fd = -1;
+		lk->owner = 0;
+		lk->on_list = 1;
+		lk->filename[0] = 0;
+		lk->next = lock_file_list;
+		lock_file_list = lk;
+	}
+
 	if (strlen(path) >= max_path_len)
 		return -1;
 	strcpy(lk->filename, path);
@@ -138,16 +154,7 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
 	strcat(lk->filename, ".lock");
 	lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666);
 	if (0 <= lk->fd) {
-		if (!lock_file_list) {
-			sigchain_push_common(remove_lock_file_on_signal);
-			atexit(remove_lock_file);
-		}
 		lk->owner = getpid();
-		if (!lk->on_list) {
-			lk->next = lock_file_list;
-			lock_file_list = lk;
-			lk->on_list = 1;
-		}
 		if (adjust_shared_perm(lk->filename)) {
 			error("cannot fix permission bits on %s", lk->filename);
 			rollback_lock_file(lk);
-- 
1.9.1