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Subject[PATCH 3/7] UBI: Fastmap: Ensure that not all anchor PEBs go into a pool.
Date
If we have no fastmap on flash make sure that not all anchor
PEBs go into a WL pool such that at least one can be used
by fastmap.

Signed-off-by: Richard Weinberger <richard@nod.at>
---
drivers/mtd/ubi/wl.c | 36 +++++++++++++++++++++++++++---------
1 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index b4d4358..8b2af8f4 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -342,16 +342,18 @@ static void prot_queue_add(struct ubi_device *ubi, struct ubi_wl_entry *e)

/**
* find_wl_entry - find wear-leveling entry closest to certain erase counter.
+ * @ubi: UBI device description object
* @root: the RB-tree where to look for
* @diff: maximum possible difference from the smallest erase counter
*
* This function looks for a wear leveling entry with erase counter closest to
* min + @diff, where min is the smallest erase counter.
*/
-static struct ubi_wl_entry *find_wl_entry(struct rb_root *root, int diff)
+static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi, struct rb_root *root,
+ int diff)
{
struct rb_node *p;
- struct ubi_wl_entry *e;
+ struct ubi_wl_entry *e, *prev_e = NULL;
int max;

e = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
@@ -366,32 +368,48 @@ static struct ubi_wl_entry *find_wl_entry(struct rb_root *root, int diff)
p = p->rb_left;
else {
p = p->rb_right;
+ prev_e = e;
e = e1;
}
}

+ /* If no fastmap has been written and this WL entry can be used
+ * as anchor PEB, hold it back and return the second best WL entry
+ * such that fastmap can use the anchor PEB later. */
+ if (!ubi->fm && e->pnum < UBI_FM_MAX_START)
+ return prev_e;
+
return e;
}

/**
* find_mean_wl_entry - find wear-leveling entry with medium erase counter.
+ * @ubi: UBI device description object
* @root: the RB-tree where to look for
*
* This function looks for a wear leveling entry with medium erase counter,
* but not greater or equivalent than the lowest erase counter plus
* %WL_FREE_MAX_DIFF/2.
*/
-static struct ubi_wl_entry *find_mean_wl_entry(struct rb_root *root)
+static struct ubi_wl_entry *find_mean_wl_entry(struct ubi_device *ubi,
+ struct rb_root *root)
{
struct ubi_wl_entry *e, *first, *last;

first = rb_entry(rb_first(root), struct ubi_wl_entry, u.rb);
last = rb_entry(rb_last(root), struct ubi_wl_entry, u.rb);

- if (last->ec - first->ec < WL_FREE_MAX_DIFF)
+ if (last->ec - first->ec < WL_FREE_MAX_DIFF) {
e = rb_entry(root->rb_node, struct ubi_wl_entry, u.rb);
+
+ /* If no fastmap has been written and this WL entry can be used
+ * as anchor PEB, hold it back and return the second best WL entry
+ * such that fastmap can use the anchor PEB later. */
+ if (e && !ubi->fm && e->pnum < UBI_FM_MAX_START)
+ e = rb_entry(rb_next(root->rb_node), struct ubi_wl_entry, u.rb);
+ }
else
- e = find_wl_entry(root, WL_FREE_MAX_DIFF/2);
+ e = find_wl_entry(ubi, root, WL_FREE_MAX_DIFF/2);

return e;
}
@@ -452,7 +470,7 @@ struct ubi_wl_entry *ubi_wl_get_fm_peb(struct ubi_device *ubi, int max_pnum)
}

if (max_pnum < 0)
- e = find_mean_wl_entry(&ubi->free);
+ e = find_mean_wl_entry(ubi, &ubi->free);
else
e = find_anchor_wl_entry(&ubi->free, max_pnum);

@@ -494,7 +512,7 @@ retry:
goto retry;
}

- e = find_mean_wl_entry(&ubi->free);
+ e = find_mean_wl_entry(ubi, &ubi->free);

self_check_in_wl_tree(ubi, e, &ubi->free);

@@ -547,7 +565,7 @@ static void refill_wl_pool(struct ubi_device *ubi)
if (!ubi->free.rb_node)
break;

- e = find_wl_entry(&ubi->free, WL_FREE_MAX_DIFF);
+ e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
self_check_in_wl_tree(ubi, e, &ubi->free);
rb_erase(&e->u.rb, &ubi->free);

@@ -1241,7 +1259,7 @@ static int ensure_wear_leveling(struct ubi_device *ubi, int nested)
* %UBI_WL_THRESHOLD.
*/
e1 = rb_entry(rb_first(&ubi->used), struct ubi_wl_entry, u.rb);
- e2 = find_wl_entry(&ubi->free, WL_FREE_MAX_DIFF);
+ e2 = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);

if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD))
goto out_unlock;
--
1.7.6.5


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