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>

2 files changed, 33 insertions, 7 deletions

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index ea9a6990a4dc..994233d6e1e3 100644
--- 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 a60f9425ab13..8421c7a9a835 100644
--- 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);