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Subject[PATCHv2] MTD: Add UBI reboot notifier
Terminate the UBI background thread prior to restarting the system.

Changes from v1:

Add ubi_sync() at the end, to make sure the underlying MTD device has
synchronized its buffers.

Clean up comments and formatting.

Signed-off-by: Kevin Cernekee <kpc.mtd@gmail.com>
---
drivers/mtd/ubi/build.c | 30 ++++++++++++++++++++++++++++++
drivers/mtd/ubi/ubi.h | 3 +++
2 files changed, 33 insertions(+), 0 deletions(-)
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 4048db8..18b42c9 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 */
@@ -726,6 +727,29 @@ 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.
+ */
+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
@@ -876,6 +900,11 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
ubi->thread_enabled = 1;
wake_up_process(ubi->bgt_thread);

+ /* 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;
return ubi_num;

@@ -945,6 +974,7 @@ 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);

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index c055511..c8fab4a 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -36,6 +36,7 @@
#include <linux/device.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
+#include <linux/notifier.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/ubi.h>

@@ -339,6 +340,7 @@ struct ubi_wl_entry;
* @bgt_thread: background thread description object
* @thread_enabled: if the background thread is enabled
* @bgt_name: background thread name
+ * @reboot_notifier: notifier to terminate background thread before rebooting
*
* @flash_size: underlying MTD device size (in bytes)
* @peb_count: count of physical eraseblocks on the MTD device
@@ -420,6 +422,7 @@ struct ubi_device {
struct task_struct *bgt_thread;
int thread_enabled;
char bgt_name[sizeof(UBI_BGT_NAME_PATTERN)+2];
+ struct notifier_block reboot_notifier;

/* I/O sub-system's stuff */
long long flash_size;
--
1.6.3.1


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