UBI: Fastmap: Ensure that only one fastmap work is scheduled

If the WL pool runs out of PEBs we schedule a fastmap write
to refill it as soon as possible.
Ensure that only one at a time is scheduled otherwise we might end in
a fastmap write storm because writing the fastmap can schedule another
write if bitflips are detected.

Signed-off-by: Richard Weinberger <richard@nod.at>
Reviewed-by: Tanya Brokhman <tlinder@codeaurora.org>
Reviewed-by: Guido Martínez <guido@vanguardiasur.com.ar>

2 files changed, 10 insertions, 2 deletions

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 2251a6c4c8fa..7a33470c0416 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -431,6 +431,7 @@ struct ubi_debug_info {
  * @fm_size: fastmap size in bytes
  * @fm_sem: allows ubi_update_fastmap() to block EBA table changes
  * @fm_work: fastmap work queue
+ * @fm_work_scheduled: non-zero if fastmap work was scheduled
  *
  * @used: RB-tree of used physical eraseblocks
  * @erroneous: RB-tree of erroneous used physical eraseblocks
@@ -442,7 +443,7 @@ struct ubi_debug_info {
  * @pq_head: protection queue head
  * @wl_lock: protects the @used, @free, @pq, @pq_head, @lookuptbl, @move_from,
  *           @move_to, @move_to_put @erase_pending, @wl_scheduled, @works,
- *           @erroneous, and @erroneous_peb_count fields
+ *           @erroneous, @erroneous_peb_count, and @fm_work_scheduled fields
  * @move_mutex: serializes eraseblock moves
  * @work_sem: used to wait for all the scheduled works to finish and prevent
  * new works from being submitted
@@ -537,6 +538,7 @@ struct ubi_device {
         void *fm_buf;
         size_t fm_size;
         struct work_struct fm_work;
+        int fm_work_scheduled;
 
         /* Wear-leveling sub-system's stuff */
         struct rb_root used;
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 0bd92d816391..ae174f4ed674 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -149,6 +149,9 @@ static void update_fastmap_work_fn(struct work_struct *wrk)
 {
         struct ubi_device *ubi = container_of(wrk, struct ubi_device, fm_work);
         ubi_update_fastmap(ubi);
+        spin_lock(&ubi->wl_lock);
+        ubi->fm_work_scheduled = 0;
+        spin_unlock(&ubi->wl_lock);
 }
 
 /**
@@ -657,7 +660,10 @@ static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
                 /* We cannot update the fastmap here because this
                  * function is called in atomic context.
                  * Let's fail here and refill/update it as soon as possible. */
-                schedule_work(&ubi->fm_work);
+                if (!ubi->fm_work_scheduled) {
+                        ubi->fm_work_scheduled = 1;
+                        schedule_work(&ubi->fm_work);
+                }
                 return NULL;
         } else {
                 pnum = pool->pebs[pool->used++];