+/*
+ * Handle "background" NFS mount [first try]
+ *
+ * Returns a valid mount command exit code.
+ *
+ * EX_BG should cause the caller to fork and invoke nfsmount_child.
+ */
+static int nfsmount_parent(struct nfsmount_info *mi)
+{
+ if (nfs_try_mount(mi))
+ return EX_SUCCESS;
+
+ /* retry background mounts when the server is not up */
+ if (nfs_is_permanent_error(errno) && errno != EOPNOTSUPP) {
+ mount_error(mi->spec, mi->node, errno);
+ return EX_FAIL;
+ }
+
+ sys_mount_errors(mi->hostname, errno, 1, 1);
+ return EX_BG;
+}
+
+/*
+ * Handle "background" NFS mount [retry daemon]
+ *
+ * Returns a valid mount command exit code: EX_SUCCESS if successful,
+ * EX_FAIL if a failure occurred. There's nothing to catch the
+ * error return, though, so we use sys_mount_errors to log the
+ * failure.
+ */
+static int nfsmount_child(struct nfsmount_info *mi)
+{
+ unsigned int secs = 1;
+ time_t timeout;
+
+ timeout = nfs_parse_retry_option(mi->options,
+ NFS_DEF_BG_TIMEOUT_MINUTES);
+
+ for (;;) {
+ if (sleep(secs))
+ break;
+ secs <<= 1;
+ if (secs > 120)
+ secs = 120;
+
+ if (nfs_try_mount(mi))
+ return EX_SUCCESS;
+
+ /* retry background mounts when the server is not up */
+ if (nfs_is_permanent_error(errno) && errno != EOPNOTSUPP)
+ break;
+
+ if (time(NULL) > timeout)
+ break;
+
+ sys_mount_errors(mi->hostname, errno, 1, 1);
+ };
+
+ sys_mount_errors(mi->hostname, errno, 1, 0);
+ return EX_FAIL;
+}
+
+/*
+ * Handle "background" NFS mount
+ *
+ * Returns a valid mount command exit code.
+ */
+static int nfsmount_bg(struct nfsmount_info *mi)
+{
+ if (!mi->child)
+ return nfsmount_parent(mi);
+ else
+ return nfsmount_child(mi);
+}
+
+/*
+ * Usually all that is needed for an NFS remount is to change
+ * generic mount options like "sync" or "ro". These generic
+ * options are controlled by mi->flags, not by text-based
+ * options, and no contact with the server is needed.
+ *
+ * Take care with the /etc/mtab entry for this mount; just
+ * calling update_mtab() will change an "-t nfs -o vers=4"
+ * mount to an "-t nfs -o remount" mount, and that will
+ * confuse umount.nfs.
+ *
+ * Returns a valid mount command exit code.
+ */
+static int nfs_remount(struct nfsmount_info *mi)
+{
+ if (nfs_sys_mount(mi, mi->options))
+ return EX_SUCCESS;
+ return EX_FAIL;
+}
+
+/*
+ * Process mount options and try a mount system call.
+ *
+ * Returns a valid mount command exit code.
+ */
+static const char *nfs_background_opttbl[] = {
+ "bg",
+ "fg",
+ NULL,
+};
+
+static int nfsmount_start(struct nfsmount_info *mi)
+{
+ if (!nfs_validate_options(mi))
+ return EX_FAIL;
+
+ /*
+ * Avoid retry and negotiation logic when remounting
+ */
+ if (mi->flags & MS_REMOUNT)
+ return nfs_remount(mi);
+
+ if (po_rightmost(mi->options, nfs_background_opttbl) == 0)
+ return nfsmount_bg(mi);
+ else
+ return nfsmount_fg(mi);
+}
+