UBI: fix ubi_wl_flush

The flush function should finish all the pending jobs. But if
somebody else is doing a work, this function should wait and let
it finish.

This patche uses rw semaphore for synchronization purpose - it
just looks quite convinient.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index ea9a699..994233d 100644 (file)
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -355,6 +355,7 @@ struct ubi_device {
        } prot;
        spinlock_t wl_lock;
        struct mutex move_mutex;
+       struct rw_semaphore work_sem;
        int wl_scheduled;
        struct ubi_wl_entry **lookuptbl;
        unsigned long long abs_ec;

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index a60f942..8421c7a 100644 (file)
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -251,10 +251,18 @@ static int do_work(struct ubi_device *ubi)
 
        cond_resched();
 
+       /*
+        * @ubi->work_sem is used to synchronize with the workers. Workers take
+        * it in read mode, so many of them may be doing works at a time. But
+        * the queue flush code has to be sure the whole queue of works is
+        * done, and it takes the mutex in write mode.
+        */
+       down_read(&ubi->work_sem);
        spin_lock(&ubi->wl_lock);
 
        if (list_empty(&ubi->works)) {
                spin_unlock(&ubi->wl_lock);
+               up_read(&ubi->work_sem);
                return 0;
        }
 
@@ -275,6 +283,7 @@ static int do_work(struct ubi_device *ubi)
        ubi->works_count -= 1;
        ubi_assert(ubi->works_count >= 0);
        spin_unlock(&ubi->wl_lock);
+       up_read(&ubi->work_sem);
        return err;
 }
 
@@ -1173,7 +1182,7 @@ retry:
                 * the WL unit has not put the PEB to the "used" tree yet, but
                 * it is about to do this. So we just set a flag which will
                 * tell the WL worker that the PEB is not needed anymore and
-                * should be sheduled for erasure.
+                * should be scheduled for erasure.
                 */
                dbg_wl("PEB %d is the target of data moving", pnum);
                ubi_assert(!ubi->move_to_put);
@@ -1280,17 +1289,32 @@ retry:
  */
 int ubi_wl_flush(struct ubi_device *ubi)
 {
-       int err, pending_count;
-
-       pending_count = ubi->works_count;
-
-       dbg_wl("flush (%d pending works)", pending_count);
+       int err;
 
        /*
         * Erase while the pending works queue is not empty, but not more then
         * the number of currently pending works.
         */
-       while (pending_count-- > 0) {
+       dbg_wl("flush (%d pending works)", ubi->works_count);
+       while (ubi->works_count) {
+               err = do_work(ubi);
+               if (err)
+                       return err;
+       }
+
+       /*
+        * Make sure all the works which have been done in parallel are
+        * finished.
+        */
+       down_write(&ubi->work_sem);
+       up_write(&ubi->work_sem);
+
+       /*
+        * And in case last was the WL worker and it cancelled the LEB
+        * movement, flush again.
+        */
+       while (ubi->works_count) {
+               dbg_wl("flush more (%d pending works)", ubi->works_count);
                err = do_work(ubi);
                if (err)
                        return err;
@@ -1426,6 +1450,7 @@ int ubi_wl_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
        ubi->prot.pnum = ubi->prot.aec = RB_ROOT;
        spin_lock_init(&ubi->wl_lock);
        mutex_init(&ubi->move_mutex);
+       init_rwsem(&ubi->work_sem);
        ubi->max_ec = si->max_ec;
        INIT_LIST_HEAD(&ubi->works);