mtd: ubi: wl: avoid erasing a PEB which is empty

wear_leveling_worker() currently unconditionally puts a PEB on erase in
the error case even it just been taken from the free_list and never
used.
In case the PEB was never used it can be put back on the free list
saving a precious erase cycle.

v1…v2:
	- to_leb_clean -> dst_leb_clean
	- use the nested option for ensure_wear_leveling()
	- do_sync_erase() can't go -ENOMEM so we can just go into
	  RO-mode now.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Richard Weinberger <richard@nod.at>

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 56065632a5b85ebf50022f883e1edc968a069f93..17ec948ac40e5c63fd8f16608ee503bc7aeee5f0 100644 (file)
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -628,6 +628,7 @@ static int do_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
        return __erase_worker(ubi, &wl_wrk);
 }
 
+static int ensure_wear_leveling(struct ubi_device *ubi, int nested);
 /**
  * wear_leveling_worker - wear-leveling worker function.
  * @ubi: UBI device description object
@@ -649,6 +650,7 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 #endif
        struct ubi_wl_entry *e1, *e2;
        struct ubi_vid_hdr *vid_hdr;
+       int dst_leb_clean = 0;
 
        kfree(wrk);
        if (shutdown)
@@ -753,6 +755,7 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 
        err = ubi_io_read_vid_hdr(ubi, e1->pnum, vid_hdr, 0);
        if (err && err != UBI_IO_BITFLIPS) {
+               dst_leb_clean = 1;
                if (err == UBI_IO_FF) {
                        /*
                         * We are trying to move PEB without a VID header. UBI
@@ -798,10 +801,12 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
                         * protection queue.
                         */
                        protect = 1;
+                       dst_leb_clean = 1;
                        goto out_not_moved;
                }
                if (err == MOVE_RETRY) {
                        scrubbing = 1;
+                       dst_leb_clean = 1;
                        goto out_not_moved;
                }
                if (err == MOVE_TARGET_BITFLIPS || err == MOVE_TARGET_WR_ERR ||
@@ -827,6 +832,7 @@ static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
                                        ubi->erroneous_peb_count);
                                goto out_error;
                        }
+                       dst_leb_clean = 1;
                        erroneous = 1;
                        goto out_not_moved;
                }
@@ -897,15 +903,24 @@ out_not_moved:
                wl_tree_add(e1, &ubi->scrub);
        else
                wl_tree_add(e1, &ubi->used);
+       if (dst_leb_clean) {
+               wl_tree_add(e2, &ubi->free);
+               ubi->free_count++;
+       }
+
        ubi_assert(!ubi->move_to_put);
        ubi->move_from = ubi->move_to = NULL;
        ubi->wl_scheduled = 0;
        spin_unlock(&ubi->wl_lock);
 
        ubi_free_vid_hdr(ubi, vid_hdr);
-       err = do_sync_erase(ubi, e2, vol_id, lnum, torture);
-       if (err)
-               goto out_ro;
+       if (dst_leb_clean) {
+               ensure_wear_leveling(ubi, 1);
+       } else {
+               err = do_sync_erase(ubi, e2, vol_id, lnum, torture);
+               if (err)
+                       goto out_ro;
+       }
 
        mutex_unlock(&ubi->move_mutex);
        return 0;