Function bg_unlink

src/replication.cpp:166–186

Plain unlink() can block for quite some time in order to actually apply * the file deletion to the filesystem. This call removes the file in a * background thread instead. We actually just do close() in the thread, * by using the fact that if there is another instance of the same file open, * the foreground unlink() will only remove the fs name, and deleting the * file's storage space will on

 * the foreground unlink() will only remove the fs name, and deleting the
 * file's storage space will only happen once the last reference is lost. */
int bg_unlink(const char *filename) {
    int fd = open(filename,O_RDONLY|O_NONBLOCK);
    if (fd == -1) {
        /* Can't open the file? Fall back to unlinking in the main thread. */
        return unlink(filename);
    } else {
        /* The following unlink() removes the name but doesn't free the
         * file contents because a process still has it open. */
        int retval = unlink(filename);
        if (retval == -1) {
            /* If we got an unlink error, we just return it, closing the
             * new reference we have to the file. */
            int old_errno = errno;
            close(fd);  /* This would overwrite our errno. So we saved it. */
            errno = old_errno;
            return -1;
        }
        bioCreateCloseJob(fd);
        return 0; /* Success. */
    }
}

/* ---------------------------------- MASTER -------------------------------- */