Re: File locks for data directory lockfile in the context of Linux namespaces

Hello!

+ if (errno == EAGAIN)
+ ereport(FATAL,
+ (errcode(ERRCODE_LOCK_FILE_EXISTS),

According to fcntl.2, this should handle both EACCESS and EAGAIN:

ERRORS
EACCES or EAGAIN
Operation is prohibited by locks held by other processes.

+static int
+OFDLockFile(int fd, const char *filename)
+...
+ else
+ return dup(fd);

Isn't this missing an FD_CLOEXEC, so that launched processes doesn't
inherit it and keep the lock open possibly longer than needed?

Also, shouldn't the code verify the result of dup? (!= -1 / errno)

+ flock_fd = OFDLockFile(fd, filename);

Can't we leak flock_fd in the stale path?

+ * Close the file descriptor, which keeps the open file description
+ * lock.
+ */
+ if (lock_file->fd > 0)
+ close(lock_file->fd);

Shouldn't this check for >= 0?

+ elog(WARNING, "Failed locking file \"%s\", %m", filename);

This probably should be:

ereport(WARNING, (errcode_for_file_access(), errmsg("could not lock
file \"%s\": %m", filename)))