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

Signed-off-by: Richard Weinberger <rich...@nod.at>
---
 drivers/mtd/ubi/ubi.h | 2 ++
 drivers/mtd/ubi/wl.c  | 8 +++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 7bf4163..529dfb0 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -426,6 +426,7 @@ 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
@@ -531,6 +532,7 @@ 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 dc01b1f..4c02a6e 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++];
-- 
2.1.0

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