UBI: add reboot notifier

Terminate the UBI background thread prior to restarting the system.

[Artem: amended comments a little]

Signed-off-by: Kevin Cernekee <kpc.mtd@gmail.com>
Tested-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 964a99d48bc4..286ed594e5a0 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -41,6 +41,7 @@
 #include <linux/miscdevice.h>
 #include <linux/log2.h>
 #include <linux/kthread.h>
+#include <linux/reboot.h>
 #include "ubi.h"
 
 /* Maximum length of the 'mtd=' parameter */
@@ -823,6 +824,34 @@ static int autoresize(struct ubi_device *ubi, int vol_id)
 }
 
 /**
+ * ubi_reboot_notifier - halt UBI transactions immediately prior to a reboot.
+ * @n: reboot notifier object
+ * @state: SYS_RESTART, SYS_HALT, or SYS_POWER_OFF
+ * @cmd: pointer to command string for RESTART2
+ *
+ * This function stops the UBI background thread so that the flash device
+ * remains quiescent when Linux restarts the system. Any queued work will be
+ * discarded, but this function will block until do_work() finishes if an
+ * operation is already in progress.
+ *
+ * This function solves a real-life problem observed on NOR flashes when an
+ * PEB erase operation starts, then the system is rebooted before the erase is
+ * finishes, and the boot loader gets confused and dies. So we prefer to finish
+ * the ongoing operation before rebooting.
+ */
+static int ubi_reboot_notifier(struct notifier_block *n, unsigned long state,
+                               void *cmd)
+{
+        struct ubi_device *ubi;
+
+        ubi = container_of(n, struct ubi_device, reboot_notifier);
+        if (ubi->bgt_thread)
+                kthread_stop(ubi->bgt_thread);
+        ubi_sync(ubi->ubi_num);
+        return NOTIFY_DONE;
+}
+
+/**
  * ubi_attach_mtd_dev - attach an MTD device.
  * @mtd: MTD device description object
  * @ubi_num: number to assign to the new UBI device
@@ -978,6 +1007,11 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
         wake_up_process(ubi->bgt_thread);
         spin_unlock(&ubi->wl_lock);
 
+        /* Flash device priority is 0 - UBI needs to shut down first */
+        ubi->reboot_notifier.priority = 1;
+        ubi->reboot_notifier.notifier_call = ubi_reboot_notifier;
+        register_reboot_notifier(&ubi->reboot_notifier);
+
         ubi_devices[ubi_num] = ubi;
         ubi_notify_all(ubi, UBI_VOLUME_ADDED, NULL);
         return ubi_num;
@@ -1049,6 +1083,7 @@ int ubi_detach_mtd_dev(int ubi_num, int anyway)
          * Before freeing anything, we have to stop the background thread to
          * prevent it from doing anything on this device while we are freeing.
          */
+        unregister_reboot_notifier(&ubi->reboot_notifier);
         if (ubi->bgt_thread)
                 kthread_stop(ubi->bgt_thread);