ubi: fastmap: Use free pebs reserved for bad block handling

If new bad PEBs occur, UBI firstly consumes ubi->beb_rsvd_pebs, and then
ubi->avail_pebs, finally UBI becomes read-only if above two items are 0,
which means that the amount of PEBs for user volumes is not effected.
Besides, UBI reserves count of free PBEs is ubi->beb_rsvd_pebs while
filling wl pool or getting free PEBs, but ubi->avail_pebs is not reserved.
So ubi->beb_rsvd_pebs and ubi->avail_pebs have nothing to do with the
usage of free PEBs, UBI can use all free PEBs.

Commit 78d6d49 ("UBI: Move fastmap specific functions out of wl.c")
has removed beb_rsvd_pebs checking while filling pool. Now, don't reserve
ubi->beb_rsvd_pebs while filling wl_pool. This will fill more PEBs in pool
and also reduce fastmap updating frequency.

Also remove beb_rsvd_pebs checking in ubi_wl_get_fm_peb.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Author: Zhihao Cheng

drivers/mtd/ubi/fastmap-wl.c

@@ -76,7 +76,7 @@ struct ubi_wl_entry *ubi_wl_get_fm_peb(struct ubi_device *ubi, int anchor)
 {
 	struct ubi_wl_entry *e = NULL;
 
-	if (!ubi->free.rb_node || (ubi->free_count - ubi->beb_rsvd_pebs < 1))
+	if (!ubi->free.rb_node)
 		goto out;
 
 	if (anchor)
@@ -100,28 +100,22 @@ struct ubi_wl_entry *ubi_wl_get_fm_peb(struct ubi_device *ubi, int anchor)
 /*
  * has_enough_free_count - whether ubi has enough free pebs to fill fm pools
  * @ubi: UBI device description object
- * @is_wl_pool: whether UBI is filling wear leveling pool
  *
  * This helper function checks whether there are enough free pebs (deducted
  * by fastmap pebs) to fill fm_pool and fm_wl_pool, above rule works after
  * there is at least one of free pebs is filled into fm_wl_pool.
- * For wear leveling pool, UBI should also reserve free pebs for bad pebs
- * handling, because there maybe no enough free pebs for user volumes after
- * producing new bad pebs.
  */
-static bool has_enough_free_count(struct ubi_device *ubi, bool is_wl_pool)
+static bool has_enough_free_count(struct ubi_device *ubi)
 {
 	int fm_used = 0;	// fastmap non anchor pebs.
-	int beb_rsvd_pebs;
 
 	if (!ubi->free.rb_node)
 		return false;
 
-	beb_rsvd_pebs = is_wl_pool ? ubi->beb_rsvd_pebs : 0;
 	if (ubi->fm_wl_pool.size > 0 && !(ubi->ro_mode || ubi->fm_disabled))
 		fm_used = ubi->fm_size / ubi->leb_size - 1;
 
-	return ubi->free_count - beb_rsvd_pebs > fm_used;
+	return ubi->free_count > fm_used;
 }
 
 /**
@@ -159,7 +153,7 @@ void ubi_refill_pools(struct ubi_device *ubi)
 	for (;;) {
 		enough = 0;
 		if (pool->size < pool->max_size) {
-			if (!has_enough_free_count(ubi, false))
+			if (!has_enough_free_count(ubi))
 				break;
 
 			e = wl_get_wle(ubi);
@@ -172,7 +166,7 @@ void ubi_refill_pools(struct ubi_device *ubi)
 			enough++;
 
 		if (wl_pool->size < wl_pool->max_size) {
-			if (!has_enough_free_count(ubi, true))
+			if (!has_enough_free_count(ubi))
 				break;
 
 			e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);