Fixes for 2 brown-paperbag bugs introduced this merge window by the fastmap

code:
 
 1. The UBI background thread got stuck when a bit-flip happened because free
    LEBs was not removed from the "free" tree when we started using it.
 2. I/O debugging checks did not work because we called a sleeping function in
    atomic context.
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Merge tag 'upstream-3.7-rc9' of git://git.infradead.org/linux-ubi

Pull UBI changes from Artem Bityutskiy:
 "Fixes for 2 brown-paperbag bugs introduced this merge window by the
  fastmap code:

   1.  The UBI background thread got stuck when a bit-flip happened
       because free LEBs was not removed from the "free" tree when we
       started using it.
   2.  I/O debugging checks did not work because we called a sleeping
       function in atomic context."

* tag 'upstream-3.7-rc9' of git://git.infradead.org/linux-ubi:
  UBI: dont call ubi_self_check_all_ff() in __wl_get_peb()
  UBI: remove PEB from free tree in get_peb_for_wl()

drivers/mtd/ubi/wl.c

@@ -498,7 +498,7 @@ out:
  * @ubi: UBI device description object
  *
  * This function returns a physical eraseblock in case of success and a
- * negative error code in case of failure. Might sleep.
+ * negative error code in case of failure.
  */
 static int __wl_get_peb(struct ubi_device *ubi)
 {
@@ -540,13 +540,6 @@ retry:
 	 * ubi_wl_get_peb() after removing e from the pool. */
 	prot_queue_add(ubi, e);
 #endif
-	err = ubi_self_check_all_ff(ubi, e->pnum, ubi->vid_hdr_aloffset,
-				    ubi->peb_size - ubi->vid_hdr_aloffset);
-	if (err) {
-		ubi_err("new PEB %d does not contain all 0xFF bytes", e->pnum);
-		return err;
-	}
-
 	return e->pnum;
 }
 
@@ -679,17 +672,30 @@ static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
 #else
 static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
 {
-	return find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
+	struct ubi_wl_entry *e;
+
+	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);
+
+	return e;
 }
 
 int ubi_wl_get_peb(struct ubi_device *ubi)
 {
-	int peb;
+	int peb, err;
 
 	spin_lock(&ubi->wl_lock);
 	peb = __wl_get_peb(ubi);
 	spin_unlock(&ubi->wl_lock);
 
+	err = ubi_self_check_all_ff(ubi, peb, ubi->vid_hdr_aloffset,
+				    ubi->peb_size - ubi->vid_hdr_aloffset);
+	if (err) {
+		ubi_err("new PEB %d does not contain all 0xFF bytes", peb);
+		return err;
+	}
+
 	return peb;
 }
 #endif