[RFC] [PATCH] UBI: refine wear leveling logic

[Alexander Schmidt <alexs@linux.vnet.ibm.com>]

Hi,

This patch addresses the handling of blocks that are put by the user
while they are moved by the wear leveling thread. The schedule_erase
function is now called by put_peb() itself instead of notifying the wear
leveling thread.

Comments are welcome...

Signed-off-by: Alexander Schmidt <alexs@linux.vnet.ibm.com>
---
 drivers/mtd/ubi/ubi.h |    2 -
 drivers/mtd/ubi/wl.c  |   77 ++++++++------------------------------------------
 2 files changed, 13 insertions(+), 66 deletions(-)

--- dedekind-ubi-2.6.orig/drivers/mtd/ubi/ubi.h
+++ dedekind-ubi-2.6/drivers/mtd/ubi/ubi.h
@@ -316,8 +316,6 @@ struct ubi_device {
 	unsigned long long abs_ec;
 	struct ubi_wl_entry *move_from;
 	struct ubi_wl_entry *move_to;
-	int move_from_put;
-	int move_to_put;
 	struct list_head works;
 	int works_count;
 	struct task_struct *bgt_thread;
--- dedekind-ubi-2.6.orig/drivers/mtd/ubi/wl.c
+++ dedekind-ubi-2.6/drivers/mtd/ubi/wl.c
@@ -793,7 +793,7 @@ static int schedule_erase(struct ubi_dev
 static int wear_leveling_worker(struct ubi_device *ubi, struct ubi_work *wrk,
 				int cancel)
 {
-	int err, put = 0;
+	int err;
 	struct ubi_wl_entry *e1, *e2;
 	struct ubi_vid_hdr *vid_hdr;
 
@@ -864,7 +864,6 @@ static int wear_leveling_worker(struct u
 
 	free_tree_del(ubi, e2);
 	ubi_assert(!ubi->move_from && !ubi->move_to);
-	ubi_assert(!ubi->move_to_put && !ubi->move_from_put);
 	ubi->move_from = e1;
 	ubi->move_to = e2;
 	spin_unlock(&ubi->wl_lock);
@@ -907,28 +906,11 @@ static int wear_leveling_worker(struct u
 
 	ubi_free_vid_hdr(ubi, vid_hdr);
 	spin_lock(&ubi->wl_lock);
-	if (unlikely(!ubi->move_to_put))
-		used_tree_add(ubi, e2);
-	else
-		put = 1;
+	used_tree_add(ubi, e2);
 	ubi->move_from = ubi->move_to = NULL;
-	ubi->move_from_put = ubi->move_to_put = 0;
 	ubi->wl_scheduled = 0;
 	spin_unlock(&ubi->wl_lock);
 
-	if (unlikely(put)) {
-		/*
-		 * Well, the target PEB was put meanwhile, schedule it for
-		 * erasure.
-		 */
-		dbg_wl("PEB %d was put meanwhile, erase", e2->pnum);
-		err = schedule_erase(ubi, e2, 0);
-		if (unlikely(err)) {
-			kmem_cache_free(wl_entries_slab, e2);
-			ubi_ro_mode(ubi);
-		}
-	}
-
 	err = schedule_erase(ubi, e1, 0);
 	if (unlikely(err)) {
 		kmem_cache_free(wl_entries_slab, e1);
@@ -950,27 +932,10 @@ error:
 	ubi_free_vid_hdr(ubi, vid_hdr);
 	spin_lock(&ubi->wl_lock);
 	ubi->wl_scheduled = 0;
-	if (ubi->move_from_put)
-		put = 1;
-	else
-		used_tree_add(ubi, e1);
+	used_tree_add(ubi, e1);
 	ubi->move_from = ubi->move_to = NULL;
-	ubi->move_from_put = ubi->move_to_put = 0;
 	spin_unlock(&ubi->wl_lock);
 
-	if (put) {
-		/*
-		 * Well, the target PEB was put meanwhile, schedule it for
-		 * erasure.
-		 */
-		dbg_wl("PEB %d was put meanwhile, erase", e1->pnum);
-		err = schedule_erase(ubi, e1, 0);
-		if (unlikely(err)) {
-			kmem_cache_free(wl_entries_slab, e1);
-			ubi_ro_mode(ubi);
-		}
-	}
-
 	err = schedule_erase(ubi, e2, 0);
 	if (unlikely(err)) {
 		kmem_cache_free(wl_entries_slab, e2);
@@ -1183,34 +1148,18 @@ int ubi_wl_put_peb(struct ubi_device *ub
 	if (unlikely(e == ubi->move_from)) {
 		/*
 		 * User is putting the physical eraseblock which was selected to
-		 * be moved. It will be scheduled for erasure in the
-		 * wear-leveling worker.
-		 */
-		dbg_wl("PEB %d is being moved", pnum);
-		ubi_assert(!ubi->move_from_put);
-		ubi->move_from_put = 1;
-		spin_unlock(&ubi->wl_lock);
-		return 0;
-	} else if (unlikely(e == ubi->move_to)) {
-		/*
-		 * User is putting the physical eraseblock which was selected
-		 * as the target the data is moved to. It may happen if the EBA
-		 * unit already re-mapped the LEB but the WL unit did has not
-		 * put the PEB to the "used" tree.
+		 * be moved. Schedule the destination block for erasure.
 		 */
-		dbg_wl("PEB %d is the target of data moving", pnum);
-		ubi_assert(!ubi->move_to_put);
-		ubi->move_to_put = 1;
-		spin_unlock(&ubi->wl_lock);
-		return 0;
-	} else {
-		if (in_wl_tree(e, &ubi->used))
-			used_tree_del(ubi, e);
-		else if (unlikely(in_wl_tree(e, &ubi->scrub)))
-			scrub_tree_del(ubi, e);
-		else
-			prot_tree_del(ubi, e->pnum);
+		dbg_wl("PEB %d is being moved");
+		e = ubi->move_to;
 	}
+
+	if (in_wl_tree(e, &ubi->used))
+		used_tree_del(ubi, e);
+	else if (unlikely(in_wl_tree(e, &ubi->scrub)))
+		scrub_tree_del(ubi, e);
+	else if (!in_wl_tree(e, &ubi->free))
+		prot_tree_del(ubi, e->pnum);
 	spin_unlock(&ubi->wl_lock);
 
 	err = schedule_erase(ubi, e, torture);