[PATCH v2 00/12] ubi: fastmap: Fix a series of wear leveling problems

[PATCH v2 00/12] ubi: fastmap: Fix a series of wear leveling problems

[Zhihao Cheng]

This series of patches fix three problems:
1. Inconsistent erase counter from wl entry and disk, for patches 1~4.
2. Same PEB is always resued for fastmap data, for patches 5~9.
3. First 64 PEBs have large erase counter than others, for patches 10~12.

Besides, patches 4/5 bring an improvement of the UBI service life.

Regression tests are in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787.

v1->v2:
  Patch 6: Change wait condition in wait_free_pebs_for_pool(), there are
	   two situations that cause waiting infinately:
	   1. __erase_worker schedules itself if -EBUSY returned when
	      shutting down system.
	   2. The 'min_expect_free' cannot be satisfied when bad block
	      occurs and ubi becomes ro(The erased PEB should be the
              last one of 'min_expect_free', but it becomes bad in
	      __erase_worker).
 PS: After re-testing, the testing results in [Link] is not affected.


Zhihao Cheng (12):
  ubi: fastmap: Fix missed ec updating after erasing old fastmap data
    block
  ubi: fastmap: erase_block: Get erase counter from wl_entry rather than
    flash
  ubi: fastmap: Allocate memory with GFP_NOFS in ubi_update_fastmap
  ubi: Replace erase_block() with sync_erase()
  ubi: fastmap: Use free pebs reserved for bad block handling
  ubi: fastmap: Wait until there are enough free PEBs before filling
    pools
  ubi: fastmap: Remove unneeded break condition while filling pools
  ubi: fastmap: may_reserve_for_fm: Don't reserve PEB if fm_anchor
    exists
  ubi: fastmap: Get wl PEB even ec beyonds the 'max' if free PEBs are
    run out
  ubi: fastmap: Fix lapsed wear leveling for first 64 PEBs
  ubi: fastmap: Add module parameter to control reserving filling pool
    PEBs
  ubi: fastmap: Add control in 'UBI_IOCATT' ioctl to reserve PEBs for
    filling pools

 drivers/mtd/ubi/build.c      |  25 +++++++-
 drivers/mtd/ubi/cdev.c       |   3 +-
 drivers/mtd/ubi/eba.c        |   3 -
 drivers/mtd/ubi/fastmap-wl.c | 112 +++++++++++++++++++++++++++--------
 drivers/mtd/ubi/fastmap.c    |  66 +++------------------
 drivers/mtd/ubi/ubi.h        |  10 +++-
 drivers/mtd/ubi/wl.c         |  48 +++++++++------
 drivers/mtd/ubi/wl.h         |   6 +-
 include/uapi/mtd/ubi-user.h  |   4 +-
 9 files changed, 164 insertions(+), 113 deletions(-)

-- 
2.39.2


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[PATCH v2 01/12] ubi: fastmap: Fix missed ec updating after erasing old fastmap data block

[Zhihao Cheng]

After running fsstress on ubifs for a long time, UBI(16384 blocks,
fastmap takes 2 blocks) has an erase block with different erase
counters displayed from two views:

From ubiscan view: PEB 8031 has erase counter 31581
=========================================================
from              to     count      min      avg      max
---------------------------------------------------------
0        ..        9:        0        0        0        0
10       ..       99:        0        0        0        0
100      ..      999:    16383      290      315      781
1000     ..     9999:        0        0        0        0
10000    ..    99999:        1    31581    31581    31581
100000   ..      inf:        0        0        0        0
---------------------------------------------------------
Total               :    16384      290      317    31581

From detailed_erase_block_info view: PEB 8031 has erase counter 7
physical_block_number   erase_count
8030                    421
8031                    7   # mem info is different from disk info
8032                    434
8033                    425
8034                    431

Following process missed updating erase counter in wl_entry(in memory):
ubi_update_fastmap
 for (i = 1; i < new_fm->used_blocks; i++) // update fastmap data
  if (!tmp_e)
   if (old_fm && old_fm->e[i])
    erase_block(ubi, old_fm->e[i]->pnum)
     ret = ubi_io_sync_erase(ubi, pnum, 0)
     ec = be64_to_cpu(ec_hdr->ec)
     ec += ret
     ec_hdr->ec = cpu_to_be64(ec)
     ubi_io_write_ec_hdr(ubi, pnum, ec_hdr)  // ec is updated on flash
   // ec is not updated in old_fm->e[i] (in memory)

Fix it by passing wl_enter into erase_block() and updating erase
counter in erase_block().

Fixes: dbb7d2a88d2a ("UBI: Add fastmap core")
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/fastmap.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
index 28c8151a0725..f8c230acc55e 100644
--- a/drivers/mtd/ubi/fastmap.c
+++ b/drivers/mtd/ubi/fastmap.c
@@ -1392,11 +1392,12 @@ static int ubi_write_fastmap(struct ubi_device *ubi,
 /**
  * erase_block - Manually erase a PEB.
  * @ubi: UBI device object
- * @pnum: PEB to be erased
+ * @e: the physical eraseblock to erase
  *
- * Returns the new EC value on success, < 0 indicates an internal error.
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
  */
-static int erase_block(struct ubi_device *ubi, int pnum)
+static int erase_block(struct ubi_device *ubi, struct ubi_wl_entry *e)
 {
 	int ret;
 	struct ubi_ec_hdr *ec_hdr;
@@ -1406,7 +1407,7 @@ static int erase_block(struct ubi_device *ubi, int pnum)
 	if (!ec_hdr)
 		return -ENOMEM;
 
-	ret = ubi_io_read_ec_hdr(ubi, pnum, ec_hdr, 0);
+	ret = ubi_io_read_ec_hdr(ubi, e->pnum, ec_hdr, 0);
 	if (ret < 0)
 		goto out;
 	else if (ret && ret != UBI_IO_BITFLIPS) {
@@ -1414,7 +1415,7 @@ static int erase_block(struct ubi_device *ubi, int pnum)
 		goto out;
 	}
 
-	ret = ubi_io_sync_erase(ubi, pnum, 0);
+	ret = ubi_io_sync_erase(ubi, e->pnum, 0);
 	if (ret < 0)
 		goto out;
 
@@ -1426,11 +1427,16 @@ static int erase_block(struct ubi_device *ubi, int pnum)
 	}
 
 	ec_hdr->ec = cpu_to_be64(ec);
-	ret = ubi_io_write_ec_hdr(ubi, pnum, ec_hdr);
+	ret = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
 	if (ret < 0)
 		goto out;
 
-	ret = ec;
+	e->ec = ec;
+	spin_lock(&ubi->wl_lock);
+	if (e->ec > ubi->max_ec)
+		ubi->max_ec = e->ec;
+	spin_unlock(&ubi->wl_lock);
+
 out:
 	kfree(ec_hdr);
 	return ret;
@@ -1576,7 +1582,7 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 
 		if (!tmp_e) {
 			if (old_fm && old_fm->e[i]) {
-				ret = erase_block(ubi, old_fm->e[i]->pnum);
+				ret = erase_block(ubi, old_fm->e[i]);
 				if (ret < 0) {
 					ubi_err(ubi, "could not erase old fastmap PEB");
 
@@ -1628,7 +1634,7 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 	if (old_fm) {
 		/* no fresh anchor PEB was found, reuse the old one */
 		if (!tmp_e) {
-			ret = erase_block(ubi, old_fm->e[0]->pnum);
+			ret = erase_block(ubi, old_fm->e[0]);
 			if (ret < 0) {
 				ubi_err(ubi, "could not erase old anchor PEB");
 
@@ -1640,7 +1646,6 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 				goto err;
 			}
 			new_fm->e[0] = old_fm->e[0];
-			new_fm->e[0]->ec = ret;
 			old_fm->e[0] = NULL;
 		} else {
 			/* we've got a new anchor PEB, return the old one */
-- 
2.39.2


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[PATCH v2 02/12] ubi: fastmap: erase_block: Get erase counter from wl_entry rather than flash

[Zhihao Cheng]

Just like sync_erase() does, getting erase counter from wl_entry is
faster than reading from flash.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/fastmap.c | 27 +++++++++------------------
 1 file changed, 9 insertions(+), 18 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
index f8c230acc55e..05ecdc049343 100644
--- a/drivers/mtd/ubi/fastmap.c
+++ b/drivers/mtd/ubi/fastmap.c
@@ -1399,36 +1399,27 @@ static int ubi_write_fastmap(struct ubi_device *ubi,
  */
 static int erase_block(struct ubi_device *ubi, struct ubi_wl_entry *e)
 {
-	int ret;
+	int err;
 	struct ubi_ec_hdr *ec_hdr;
-	long long ec;
+	long long ec = e->ec;
 
 	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
 	if (!ec_hdr)
 		return -ENOMEM;
 
-	ret = ubi_io_read_ec_hdr(ubi, e->pnum, ec_hdr, 0);
-	if (ret < 0)
-		goto out;
-	else if (ret && ret != UBI_IO_BITFLIPS) {
-		ret = -EINVAL;
-		goto out;
-	}
-
-	ret = ubi_io_sync_erase(ubi, e->pnum, 0);
-	if (ret < 0)
+	err = ubi_io_sync_erase(ubi, e->pnum, 0);
+	if (err < 0)
 		goto out;
 
-	ec = be64_to_cpu(ec_hdr->ec);
-	ec += ret;
+	ec += err;
 	if (ec > UBI_MAX_ERASECOUNTER) {
-		ret = -EINVAL;
+		err = -EINVAL;
 		goto out;
 	}
 
 	ec_hdr->ec = cpu_to_be64(ec);
-	ret = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
-	if (ret < 0)
+	err = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
+	if (err < 0)
 		goto out;
 
 	e->ec = ec;
@@ -1439,7 +1430,7 @@ static int erase_block(struct ubi_device *ubi, struct ubi_wl_entry *e)
 
 out:
 	kfree(ec_hdr);
-	return ret;
+	return err;
 }
 
 /**
-- 
2.39.2


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[PATCH v2 03/12] ubi: fastmap: Allocate memory with GFP_NOFS in ubi_update_fastmap

[Zhihao Cheng]

Function ubi_update_fastmap could be called in IO context, for example:
 ubifs_writepage
  do_writepage
   ubifs_jnl_write_data
    write_head
     ubifs_wbuf_write_nolock
      ubifs_leb_write
       ubi_leb_write
        ubi_eba_write_leb
	 try_write_vid_and_data
	  ubi_wl_get_peb
	   ubi_update_fastmap
	    erase_block

So it's better to allocate memory with GFP_NOFS mode, in case waiting
page writeback(dead loop).

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/fastmap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
index 05ecdc049343..d64bfb986d40 100644
--- a/drivers/mtd/ubi/fastmap.c
+++ b/drivers/mtd/ubi/fastmap.c
@@ -20,7 +20,7 @@ static inline unsigned long *init_seen(struct ubi_device *ubi)
 	if (!ubi_dbg_chk_fastmap(ubi))
 		return NULL;
 
-	ret = bitmap_zalloc(ubi->peb_count, GFP_KERNEL);
+	ret = bitmap_zalloc(ubi->peb_count, GFP_NOFS);
 	if (!ret)
 		return ERR_PTR(-ENOMEM);
 
@@ -105,7 +105,7 @@ static struct ubi_vid_io_buf *new_fm_vbuf(struct ubi_device *ubi, int vol_id)
 	struct ubi_vid_io_buf *new;
 	struct ubi_vid_hdr *vh;
 
-	new = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+	new = ubi_alloc_vid_buf(ubi, GFP_NOFS);
 	if (!new)
 		goto out;
 
@@ -1403,7 +1403,7 @@ static int erase_block(struct ubi_device *ubi, struct ubi_wl_entry *e)
 	struct ubi_ec_hdr *ec_hdr;
 	long long ec = e->ec;
 
-	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
+	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
 	if (!ec_hdr)
 		return -ENOMEM;
 
@@ -1459,7 +1459,7 @@ static int invalidate_fastmap(struct ubi_device *ubi)
 	ubi->fm = NULL;
 
 	ret = -ENOMEM;
-	fm = kzalloc(sizeof(*fm), GFP_KERNEL);
+	fm = kzalloc(sizeof(*fm), GFP_NOFS);
 	if (!fm)
 		goto out;
 
@@ -1548,7 +1548,7 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 		return 0;
 	}
 
-	new_fm = kzalloc(sizeof(*new_fm), GFP_KERNEL);
+	new_fm = kzalloc(sizeof(*new_fm), GFP_NOFS);
 	if (!new_fm) {
 		up_write(&ubi->fm_eba_sem);
 		up_write(&ubi->work_sem);
-- 
2.39.2


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[PATCH v2 04/12] ubi: Replace erase_block() with sync_erase()

[Zhihao Cheng]

Since erase_block() has same logic with sync_erase(), just replace it
with sync_erase(), also rename 'sync_erase()' to 'ubi_sync_erase()'.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/fastmap.c | 48 ++-------------------------------------
 drivers/mtd/ubi/ubi.h     |  1 +
 drivers/mtd/ubi/wl.c      |  9 ++++----
 3 files changed, 7 insertions(+), 51 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
index d64bfb986d40..8f6052cb3217 100644
--- a/drivers/mtd/ubi/fastmap.c
+++ b/drivers/mtd/ubi/fastmap.c
@@ -1389,50 +1389,6 @@ static int ubi_write_fastmap(struct ubi_device *ubi,
 	return ret;
 }
 
-/**
- * erase_block - Manually erase a PEB.
- * @ubi: UBI device object
- * @e: the physical eraseblock to erase
- *
- * This function returns zero in case of success and a negative error code in
- * case of failure.
- */
-static int erase_block(struct ubi_device *ubi, struct ubi_wl_entry *e)
-{
-	int err;
-	struct ubi_ec_hdr *ec_hdr;
-	long long ec = e->ec;
-
-	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_NOFS);
-	if (!ec_hdr)
-		return -ENOMEM;
-
-	err = ubi_io_sync_erase(ubi, e->pnum, 0);
-	if (err < 0)
-		goto out;
-
-	ec += err;
-	if (ec > UBI_MAX_ERASECOUNTER) {
-		err = -EINVAL;
-		goto out;
-	}
-
-	ec_hdr->ec = cpu_to_be64(ec);
-	err = ubi_io_write_ec_hdr(ubi, e->pnum, ec_hdr);
-	if (err < 0)
-		goto out;
-
-	e->ec = ec;
-	spin_lock(&ubi->wl_lock);
-	if (e->ec > ubi->max_ec)
-		ubi->max_ec = e->ec;
-	spin_unlock(&ubi->wl_lock);
-
-out:
-	kfree(ec_hdr);
-	return err;
-}
-
 /**
  * invalidate_fastmap - destroys a fastmap.
  * @ubi: UBI device object
@@ -1573,7 +1529,7 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 
 		if (!tmp_e) {
 			if (old_fm && old_fm->e[i]) {
-				ret = erase_block(ubi, old_fm->e[i]);
+				ret = ubi_sync_erase(ubi, old_fm->e[i], 0);
 				if (ret < 0) {
 					ubi_err(ubi, "could not erase old fastmap PEB");
 
@@ -1625,7 +1581,7 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 	if (old_fm) {
 		/* no fresh anchor PEB was found, reuse the old one */
 		if (!tmp_e) {
-			ret = erase_block(ubi, old_fm->e[0]);
+			ret = ubi_sync_erase(ubi, old_fm->e[0], 0);
 			if (ret < 0) {
 				ubi_err(ubi, "could not erase old anchor PEB");
 
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index c8f1bd4fa100..2f0c0eacc013 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -902,6 +902,7 @@ int self_check_eba(struct ubi_device *ubi, struct ubi_attach_info *ai_fastmap,
 		   struct ubi_attach_info *ai_scan);
 
 /* wl.c */
+int ubi_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e, int torture);
 int ubi_wl_get_peb(struct ubi_device *ubi);
 int ubi_wl_put_peb(struct ubi_device *ubi, int vol_id, int lnum,
 		   int pnum, int torture);
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 26a214f016c1..0c78e09d7960 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -427,7 +427,7 @@ static int prot_queue_del(struct ubi_device *ubi, int pnum)
 }
 
 /**
- * sync_erase - synchronously erase a physical eraseblock.
+ * ubi_sync_erase - synchronously erase a physical eraseblock.
  * @ubi: UBI device description object
  * @e: the physical eraseblock to erase
  * @torture: if the physical eraseblock has to be tortured
@@ -435,8 +435,7 @@ static int prot_queue_del(struct ubi_device *ubi, int pnum)
  * This function returns zero in case of success and a negative error code in
  * case of failure.
  */
-static int sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e,
-		      int torture)
+int ubi_sync_erase(struct ubi_device *ubi, struct ubi_wl_entry *e, int torture)
 {
 	int err;
 	struct ubi_ec_hdr *ec_hdr;
@@ -1094,7 +1093,7 @@ static int __erase_worker(struct ubi_device *ubi, struct ubi_work *wl_wrk)
 	dbg_wl("erase PEB %d EC %d LEB %d:%d",
 	       pnum, e->ec, wl_wrk->vol_id, wl_wrk->lnum);
 
-	err = sync_erase(ubi, e, wl_wrk->torture);
+	err = ubi_sync_erase(ubi, e, wl_wrk->torture);
 	if (!err) {
 		spin_lock(&ubi->wl_lock);
 
@@ -1749,7 +1748,7 @@ static int erase_aeb(struct ubi_device *ubi, struct ubi_ainf_peb *aeb, bool sync
 	ubi->lookuptbl[e->pnum] = e;
 
 	if (sync) {
-		err = sync_erase(ubi, e, false);
+		err = ubi_sync_erase(ubi, e, false);
 		if (err)
 			goto out_free;
 
-- 
2.39.2


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[PATCH v2 05/12] ubi: fastmap: Use free pebs reserved for bad block handling

[Zhihao Cheng]

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 78d6d497a648 ("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>
---
 drivers/mtd/ubi/fastmap-wl.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
index 863f571f1adb..4611a75f1241 100644
--- a/drivers/mtd/ubi/fastmap-wl.c
+++ b/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);
-- 
2.39.2


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[PATCH v2 06/12] ubi: fastmap: Wait until there are enough free PEBs before filling pools

[Zhihao Cheng]

Wait until there are enough free PEBs before filling pool/wl_pool,
sometimes erase_worker is not scheduled in time, which causes two
situations:
 A. There are few PEBs filled in pool, which makes ubi_update_fastmap
    is frequently called and leads first 64 PEBs are erased more times
    than other PEBs. So waiting free PEBs before filling pool reduces
    fastmap updating frequency and prolongs flash service life.
 B. In situation that space is nearly running out, ubi_refill_pools()
    cannot make sure pool and wl_pool are filled with free PEBs, caused
    by the delay of erase_worker. After this patch applied, there must
    exist free PEBs in pool after one call of ubi_update_fastmap.

Besides, this patch is a preparetion for fixing large erase counter in
fastmap data block and fixing lapsed wear leveling for first 64 PEBs.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 v1->v2: Change waiting conditions.
 drivers/mtd/ubi/eba.c        |  3 --
 drivers/mtd/ubi/fastmap-wl.c | 53 ++++++++++++++++++++++++++++++++++--
 drivers/mtd/ubi/fastmap.c    |  6 +---
 drivers/mtd/ubi/ubi.h        |  5 +++-
 drivers/mtd/ubi/wl.c         | 14 +++++++---
 5 files changed, 65 insertions(+), 16 deletions(-)

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 655ff41863e2..8d1f0e05892c 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -33,9 +33,6 @@
 #include <linux/err.h>
 #include "ubi.h"
 
-/* Number of physical eraseblocks reserved for atomic LEB change operation */
-#define EBA_RESERVED_PEBS 1
-
 /**
  * struct ubi_eba_entry - structure encoding a single LEB -> PEB association
  * @pnum: the physical eraseblock number attached to the LEB
diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
index 4611a75f1241..12854717915a 100644
--- a/drivers/mtd/ubi/fastmap-wl.c
+++ b/drivers/mtd/ubi/fastmap-wl.c
@@ -97,6 +97,46 @@ struct ubi_wl_entry *ubi_wl_get_fm_peb(struct ubi_device *ubi, int anchor)
 	return e;
 }
 
+/*
+ * wait_free_pebs_for_pool - wait until there enough free pebs
+ * @ubi: UBI device description object
+ *
+ * Wait and execute do_work until there are enough free pebs, fill pool
+ * as much as we can. This will reduce pool refilling times, which can
+ * reduce the fastmap updating frequency.
+ */
+static void wait_free_pebs_for_pool(struct ubi_device *ubi)
+{
+	struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;
+	struct ubi_fm_pool *pool = &ubi->fm_pool;
+	int free, expect_free, executed;
+	/*
+	 * There are at least following free pebs which reserved by UBI:
+	 * 1. WL_RESERVED_PEBS[1]
+	 * 2. EBA_RESERVED_PEBS[1]
+	 * 3. fm pebs - 1: Twice fastmap size deducted by fastmap and fm_anchor
+	 * 4. beb_rsvd_pebs: This value should be get under lock ubi->wl_lock
+	 */
+	int reserved = WL_RESERVED_PEBS + EBA_RESERVED_PEBS +
+		       ubi->fm_size / ubi->leb_size - 1;
+
+	do {
+		spin_lock(&ubi->wl_lock);
+		free = ubi->free_count;
+		free += pool->size - pool->used + wl_pool->size - wl_pool->used;
+		expect_free = reserved + ubi->beb_rsvd_pebs;
+		spin_unlock(&ubi->wl_lock);
+
+		/*
+		 * Break out if there are no works or work is executed failure,
+		 * given the fact that erase_worker will schedule itself when
+		 * -EBUSY is returned from mtd layer caused by system shutdown.
+		 */
+		if (do_work(ubi, &executed) || !executed)
+			break;
+	} while (free < expect_free);
+}
+
 /*
  * has_enough_free_count - whether ubi has enough free pebs to fill fm pools
  * @ubi: UBI device description object
@@ -119,16 +159,23 @@ static bool has_enough_free_count(struct ubi_device *ubi)
 }
 
 /**
- * ubi_refill_pools - refills all fastmap PEB pools.
+ * ubi_refill_pools_and_lock - refills all fastmap PEB pools and takes fm locks.
  * @ubi: UBI device description object
  */
-void ubi_refill_pools(struct ubi_device *ubi)
+void ubi_refill_pools_and_lock(struct ubi_device *ubi)
 {
 	struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;
 	struct ubi_fm_pool *pool = &ubi->fm_pool;
 	struct ubi_wl_entry *e;
 	int enough;
 
+	if (!ubi->ro_mode && !ubi->fm_disabled)
+		wait_free_pebs_for_pool(ubi);
+
+	down_write(&ubi->fm_protect);
+	down_write(&ubi->work_sem);
+	down_write(&ubi->fm_eba_sem);
+
 	spin_lock(&ubi->wl_lock);
 
 	return_unused_pool_pebs(ubi, wl_pool);
@@ -204,7 +251,7 @@ static int produce_free_peb(struct ubi_device *ubi)
 
 	while (!ubi->free.rb_node && ubi->works_count) {
 		dbg_wl("do one work synchronously");
-		err = do_work(ubi);
+		err = do_work(ubi, NULL);
 
 		if (err)
 			return err;
diff --git a/drivers/mtd/ubi/fastmap.c b/drivers/mtd/ubi/fastmap.c
index 8f6052cb3217..2a728c31e6b8 100644
--- a/drivers/mtd/ubi/fastmap.c
+++ b/drivers/mtd/ubi/fastmap.c
@@ -1491,11 +1491,7 @@ int ubi_update_fastmap(struct ubi_device *ubi)
 	struct ubi_fastmap_layout *new_fm, *old_fm;
 	struct ubi_wl_entry *tmp_e;
 
-	down_write(&ubi->fm_protect);
-	down_write(&ubi->work_sem);
-	down_write(&ubi->fm_eba_sem);
-
-	ubi_refill_pools(ubi);
+	ubi_refill_pools_and_lock(ubi);
 
 	if (ubi->ro_mode || ubi->fm_disabled) {
 		up_write(&ubi->fm_eba_sem);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 2f0c0eacc013..423f66c91b1d 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -82,6 +82,9 @@ void ubi_err(const struct ubi_device *ubi, const char *fmt, ...);
 #define UBI_DFS_DIR_NAME "ubi%d"
 #define UBI_DFS_DIR_LEN  (3 + 2 + 1)
 
+/* Number of physical eraseblocks reserved for atomic LEB change operation */
+#define EBA_RESERVED_PEBS 1
+
 /*
  * Error codes returned by the I/O sub-system.
  *
@@ -915,7 +918,7 @@ struct ubi_wl_entry *ubi_wl_get_fm_peb(struct ubi_device *ubi, int anchor);
 int ubi_wl_put_fm_peb(struct ubi_device *ubi, struct ubi_wl_entry *used_e,
 		      int lnum, int torture);
 int ubi_is_erase_work(struct ubi_work *wrk);
-void ubi_refill_pools(struct ubi_device *ubi);
+void ubi_refill_pools_and_lock(struct ubi_device *ubi);
 int ubi_ensure_anchor_pebs(struct ubi_device *ubi);
 int ubi_bitflip_check(struct ubi_device *ubi, int pnum, int force_scrub);
 
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 0c78e09d7960..14edb65ce6a6 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -181,11 +181,13 @@ static void wl_entry_destroy(struct ubi_device *ubi, struct ubi_wl_entry *e)
 /**
  * do_work - do one pending work.
  * @ubi: UBI device description object
+ * @executed: whether there is one work is executed
  *
  * This function returns zero in case of success and a negative error code in
- * case of failure.
+ * case of failure. If @executed is not NULL and there is one work executed,
+ * @executed is set as %1, otherwise @executed is set as %0.
  */
-static int do_work(struct ubi_device *ubi)
+static int do_work(struct ubi_device *ubi, int *executed)
 {
 	int err;
 	struct ubi_work *wrk;
@@ -203,9 +205,13 @@ static int do_work(struct ubi_device *ubi)
 	if (list_empty(&ubi->works)) {
 		spin_unlock(&ubi->wl_lock);
 		up_read(&ubi->work_sem);
+		if (executed)
+			*executed = 0;
 		return 0;
 	}
 
+	if (executed)
+		*executed = 1;
 	wrk = list_entry(ubi->works.next, struct ubi_work, list);
 	list_del(&wrk->list);
 	ubi->works_count -= 1;
@@ -1685,7 +1691,7 @@ int ubi_thread(void *u)
 		}
 		spin_unlock(&ubi->wl_lock);
 
-		err = do_work(ubi);
+		err = do_work(ubi, NULL);
 		if (err) {
 			ubi_err(ubi, "%s: work failed with error code %d",
 				ubi->bgt_name, err);
@@ -2096,7 +2102,7 @@ static int produce_free_peb(struct ubi_device *ubi)
 		spin_unlock(&ubi->wl_lock);
 
 		dbg_wl("do one work synchronously");
-		err = do_work(ubi);
+		err = do_work(ubi, NULL);
 
 		spin_lock(&ubi->wl_lock);
 		if (err)
-- 
2.39.2


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[PATCH v2 07/12] ubi: fastmap: Remove unneeded break condition while filling pools

[Zhihao Cheng]

Change pool filling stop condition. Commit d09e9a2bddba ("ubi:
fastmap: Fix high cpu usage of ubi_bgt by making sure wl_pool
not empty") reserves fastmap data PEBs after filling 1 PEB in
wl_pool. Now wait_free_pebs_for_pool() makes enough free PEBs
before filling pool, there will still be at least 1 PEB in pool
and 1 PEB in wl_pool after doing ubi_refill_pools().

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/fastmap-wl.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
index 12854717915a..7c4cfd80da31 100644
--- a/drivers/mtd/ubi/fastmap-wl.c
+++ b/drivers/mtd/ubi/fastmap-wl.c
@@ -142,8 +142,7 @@ static void wait_free_pebs_for_pool(struct ubi_device *ubi)
  * @ubi: UBI device description object
  *
  * 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.
+ * by fastmap pebs) to fill fm_pool and fm_wl_pool.
  */
 static bool has_enough_free_count(struct ubi_device *ubi)
 {
@@ -152,7 +151,7 @@ static bool has_enough_free_count(struct ubi_device *ubi)
 	if (!ubi->free.rb_node)
 		return false;
 
-	if (ubi->fm_wl_pool.size > 0 && !(ubi->ro_mode || ubi->fm_disabled))
+	if (!ubi->ro_mode && !ubi->fm_disabled)
 		fm_used = ubi->fm_size / ubi->leb_size - 1;
 
 	return ubi->free_count > fm_used;
-- 
2.39.2


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[PATCH v2 08/12] ubi: fastmap: may_reserve_for_fm: Don't reserve PEB if fm_anchor exists

[Zhihao Cheng]

This is the part 1 to fix cyclically reusing single fastmap data PEBs.

After running fsstress on UBIFS for a while, UBI (16384 blocks, fastmap
takes 2 blocks) has an erase block(PEB: 8031) with big erase counter
greater than any other pebs:

=========================================================
from              to     count      min      avg      max
---------------------------------------------------------
0        ..        9:        0        0        0        0
10       ..       99:      532       84       92       99
100      ..      999:    15787      100      147      229
1000     ..     9999:       64     4699     4765     4826
10000    ..    99999:        0        0        0        0
100000   ..      inf:        1   272935   272935   272935
---------------------------------------------------------
Total               :    16384       84      180   272935

Not like fm_anchor, there is no candidate PEBs for fastmap data area,
so old fastmap data pebs will be reused after all free pebs are filled
into pool/wl_pool:
ubi_update_fastmap
 for (i = 1; i < new_fm->used_blocks; i++)
  erase_block(ubi, old_fm->e[i]->pnum)
  new_fm->e[i] = old_fm->e[i]

According to wear leveling algorithm, UBI selects one small erase
counter PEB from ubi->used and one big erase counter PEB from wl_pool,
the reused fastmap data PEB is not in these trees. UBI won't schedule
this PEB for wl even it is in ubi->used because wl algorithm expects
small erase counter for used PEB.

Don't reserve PEB for fastmap in may_reserve_for_fm() if fm_anchor
already exists. Otherwise, when UBI is running out of free PEBs,
the only one free PEB (pnum < 64) will be skipped and fastmap data
will be written on the same old PEB.

Fixes: dbb7d2a88d2a ("UBI: Add fastmap core")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/fastmap-wl.c | 2 +-
 drivers/mtd/ubi/wl.c         | 9 ++++++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
index 7c4cfd80da31..490514da1e00 100644
--- a/drivers/mtd/ubi/fastmap-wl.c
+++ b/drivers/mtd/ubi/fastmap-wl.c
@@ -521,7 +521,7 @@ static void ubi_fastmap_close(struct ubi_device *ubi)
 static struct ubi_wl_entry *may_reserve_for_fm(struct ubi_device *ubi,
 					   struct ubi_wl_entry *e,
 					   struct rb_root *root) {
-	if (e && !ubi->fm_disabled && !ubi->fm &&
+	if (e && !ubi->fm_disabled && !ubi->fm && !ubi->fm_anchor &&
 	    e->pnum < UBI_FM_MAX_START)
 		e = rb_entry(rb_next(root->rb_node),
 			     struct ubi_wl_entry, u.rb);
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 14edb65ce6a6..40a1c306b8af 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -367,9 +367,12 @@ static struct ubi_wl_entry *find_mean_wl_entry(struct ubi_device *ubi,
 	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 no fastmap has been written and fm_anchor is not
+		 * reserved 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.
+		 */
 		e = may_reserve_for_fm(ubi, e, root);
 	} else
 		e = find_wl_entry(ubi, root, WL_FREE_MAX_DIFF/2);
-- 
2.39.2


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[PATCH v2 09/12] ubi: fastmap: Get wl PEB even ec beyonds the 'max' if free PEBs are run out

[Zhihao Cheng]

This is the part 2 to fix cyclically reusing single fastmap data PEBs.

Consider one situation, if there are four free PEBs for fm_anchor, pool,
wl_pool and fastmap data PEB with erase counter 100, 100, 100, 5096
(ubi->beb_rsvd_pebs is 0). PEB with erase counter 5096 is always picked
for fastmap data according to the realization of find_wl_entry(), since
fastmap data PEB is not scheduled for wl, finally there are two PEBs
(fm data) with great erase counter than other PEBS.
Get wl PEB even its erase counter exceeds the 'max' in find_wl_entry()
when free PEBs are run out after filling pools and fm data. Then the PEB
with biggest erase conter is taken as wl PEB, it can be scheduled for wl.

Fixes: dbb7d2a88d2a ("UBI: Add fastmap core")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/fastmap-wl.c | 44 ++++++++++++++++++++++++++++--------
 drivers/mtd/ubi/wl.c         | 16 ++++++++-----
 2 files changed, 44 insertions(+), 16 deletions(-)

diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
index 490514da1e00..03c1f1016c0a 100644
--- a/drivers/mtd/ubi/fastmap-wl.c
+++ b/drivers/mtd/ubi/fastmap-wl.c
@@ -138,23 +138,44 @@ static void wait_free_pebs_for_pool(struct ubi_device *ubi)
 }
 
 /*
- * has_enough_free_count - whether ubi has enough free pebs to fill fm pools
+ * left_free_count - returns the number of free pebs to fill fm pools
  * @ubi: UBI device description object
  *
- * This helper function checks whether there are enough free pebs (deducted
+ * This helper function returns the number of free pebs (deducted
  * by fastmap pebs) to fill fm_pool and fm_wl_pool.
  */
-static bool has_enough_free_count(struct ubi_device *ubi)
+static int left_free_count(struct ubi_device *ubi)
 {
 	int fm_used = 0;	// fastmap non anchor pebs.
 
 	if (!ubi->free.rb_node)
-		return false;
+		return 0;
 
 	if (!ubi->ro_mode && !ubi->fm_disabled)
 		fm_used = ubi->fm_size / ubi->leb_size - 1;
 
-	return ubi->free_count > fm_used;
+	return ubi->free_count - fm_used;
+}
+
+/*
+ * can_fill_pools - whether free PEBs will be left after filling pools
+ * @ubi: UBI device description object
+ * @free: current number of free PEBs
+ *
+ * Return %1 if there are still left free PEBs after filling pools,
+ * otherwise %0 is returned.
+ */
+static int can_fill_pools(struct ubi_device *ubi, int free)
+{
+	struct ubi_fm_pool *wl_pool = &ubi->fm_wl_pool;
+	struct ubi_fm_pool *pool = &ubi->fm_pool;
+	int pool_need = pool->max_size - pool->size +
+			wl_pool->max_size - wl_pool->size;
+
+	if (free - pool_need < 1)
+		return 0;
+
+	return 1;
 }
 
 /**
@@ -199,7 +220,7 @@ void ubi_refill_pools_and_lock(struct ubi_device *ubi)
 	for (;;) {
 		enough = 0;
 		if (pool->size < pool->max_size) {
-			if (!has_enough_free_count(ubi))
+			if (left_free_count(ubi) <= 0)
 				break;
 
 			e = wl_get_wle(ubi);
@@ -212,10 +233,13 @@ void ubi_refill_pools_and_lock(struct ubi_device *ubi)
 			enough++;
 
 		if (wl_pool->size < wl_pool->max_size) {
-			if (!has_enough_free_count(ubi))
+			int left_free = left_free_count(ubi);
+
+			if (left_free <= 0)
 				break;
 
-			e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
+			e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF,
+					  !can_fill_pools(ubi, left_free));
 			self_check_in_wl_tree(ubi, e, &ubi->free);
 			rb_erase(&e->u.rb, &ubi->free);
 			ubi->free_count--;
@@ -355,12 +379,12 @@ static bool need_wear_leveling(struct ubi_device *ubi)
 	if (!e) {
 		if (!ubi->free.rb_node)
 			return false;
-		e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
+		e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);
 		ec = e->ec;
 	} else {
 		ec = e->ec;
 		if (ubi->free.rb_node) {
-			e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
+			e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);
 			ec = max(ec, e->ec);
 		}
 	}
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 40a1c306b8af..a357f3d27f2f 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -317,12 +317,14 @@ static void prot_queue_add(struct ubi_device *ubi, struct ubi_wl_entry *e)
  * @ubi: UBI device description object
  * @root: the RB-tree where to look for
  * @diff: maximum possible difference from the smallest erase counter
+ * @pick_max: pick PEB even its erase counter beyonds 'min_ec + @diff'
  *
  * 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 ubi_device *ubi,
-					  struct rb_root *root, int diff)
+					  struct rb_root *root, int diff,
+					  int pick_max)
 {
 	struct rb_node *p;
 	struct ubi_wl_entry *e;
@@ -336,9 +338,11 @@ static struct ubi_wl_entry *find_wl_entry(struct ubi_device *ubi,
 		struct ubi_wl_entry *e1;
 
 		e1 = rb_entry(p, struct ubi_wl_entry, u.rb);
-		if (e1->ec >= max)
+		if (e1->ec >= max) {
+			if (pick_max)
+				e = e1;
 			p = p->rb_left;
-		else {
+		} else {
 			p = p->rb_right;
 			e = e1;
 		}
@@ -375,7 +379,7 @@ static struct ubi_wl_entry *find_mean_wl_entry(struct ubi_device *ubi,
 		 */
 		e = may_reserve_for_fm(ubi, e, root);
 	} else
-		e = find_wl_entry(ubi, root, WL_FREE_MAX_DIFF/2);
+		e = find_wl_entry(ubi, root, WL_FREE_MAX_DIFF/2, 0);
 
 	return e;
 }
@@ -1048,7 +1052,7 @@ 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, &ubi->free, WL_FREE_MAX_DIFF);
+		e2 = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);
 
 		if (!(e2->ec - e1->ec >= UBI_WL_THRESHOLD))
 			goto out_unlock;
@@ -2079,7 +2083,7 @@ static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
 {
 	struct ubi_wl_entry *e;
 
-	e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF);
+	e = find_wl_entry(ubi, &ubi->free, WL_FREE_MAX_DIFF, 0);
 	self_check_in_wl_tree(ubi, e, &ubi->free);
 	ubi->free_count--;
 	ubi_assert(ubi->free_count >= 0);
-- 
2.39.2


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[PATCH v2 10/12] ubi: fastmap: Fix lapsed wear leveling for first 64 PEBs

[Zhihao Cheng]

The anchor PEB must be picked from first 64 PEBs, these PEBs could have
large erase counter greater than other PEBs especially when free space
is nearly running out.
The ubi_update_fastmap will be called as long as pool/wl_pool is empty,
old anchor PEB is erased when updating fastmap. Given an UBI device with
N PEBs, free PEBs is nearly running out and pool will be filled with 1
PEB every time ubi_update_fastmap invoked. So t=N/POOL_SIZE[1]/64 means
that in worst case the erase counter of first 64 PEBs is t times greater
than other PEBs in theory.
After running fsstress for 24h, the erase counter statistics for two UBI
devices shown as follow(CONFIG_MTD_UBI_WL_THRESHOLD=128):

Device A(1024 PEBs, pool=50, wl_pool=25):
=========================================================
from              to     count      min      avg      max
---------------------------------------------------------
0        ..        9:        0        0        0        0
10       ..       99:        0        0        0        0
100      ..      999:        0        0        0        0
1000     ..     9999:        0        0        0        0
10000    ..    99999:      960    29224    29282    29362
100000   ..      inf:       64   117897   117934   117940
---------------------------------------------------------
Total               :     1024    29224    34822   117940

Device B(8192 PEBs, pool=256, wl_pool=128):
=========================================================
from              to     count      min      avg      max
---------------------------------------------------------
0        ..        9:        0        0        0        0
10       ..       99:        0        0        0        0
100      ..      999:        0        0        0        0
1000     ..     9999:     8128     2253     2321     2387
10000    ..    99999:       64    35387    35387    35388
100000   ..      inf:        0        0        0        0
---------------------------------------------------------
Total               :     8192     2253     2579    35388

The key point is reducing fastmap updating frequency by enlarging
POOL_SIZE, so let UBI reserve ubi->fm_pool.max_size PEBs during
attaching. Then POOL_SIZE will become ubi->fm_pool.max_size/2 even
in free space running out case.
Given an UBI device with 8192 PEBs(16384\8192\4096 is common
large-capacity flash), t=8192/128/64=1. The fastmap updating will
happen in either wl_pool or pool is empty, so setting fm_pool_rsv_cnt
as ubi->fm_pool.max_size can fill wl_pool in full state.

After pool reservation, running fsstress for 24h:

Device A(1024 PEBs, pool=50, wl_pool=25):
=========================================================
from              to     count      min      avg      max
---------------------------------------------------------
0        ..        9:        0        0        0        0
10       ..       99:        0        0        0        0
100      ..      999:        0        0        0        0
1000     ..     9999:        0        0        0        0
10000    ..    99999:     1024    33801    33997    34056
100000   ..      inf:        0        0        0        0
---------------------------------------------------------
Total               :     1024    33801    33997    34056

Device B(8192 PEBs, pool=256, wl_pool=128):
=========================================================
from              to     count      min      avg      max
---------------------------------------------------------
0        ..        9:        0        0        0        0
10       ..       99:        0        0        0        0
100      ..      999:        0        0        0        0
1000     ..     9999:     8192     2205     2397     2460
10000    ..    99999:        0        0        0        0
100000   ..      inf:        0        0        0        0
---------------------------------------------------------
Total               :     8192     2205     2397     2460

The difference of erase counter between first 64 PEBs and others is
under WL_FREE_MAX_DIFF(2*UBI_WL_THRESHOLD=2*128=256).
  Device A: 34056 - 33801 = 255
  Device B: 2460 - 2205 = 255

Next patch will add a switch to control whether UBI needs to reserve
PEBs for filling pool.

Fixes: dbb7d2a88d2a ("UBI: Add fastmap core")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/build.c      | 1 +
 drivers/mtd/ubi/fastmap-wl.c | 2 +-
 drivers/mtd/ubi/ubi.h        | 2 ++
 drivers/mtd/ubi/wl.h         | 6 ++++--
 4 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 8ee51e49fced..66d7b6a16aad 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -951,6 +951,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 		UBI_FM_MIN_POOL_SIZE);
 
 	ubi->fm_wl_pool.max_size = ubi->fm_pool.max_size / 2;
+	ubi->fm_pool_rsv_cnt = ubi->fm_pool.max_size;
 	ubi->fm_disabled = (!fm_autoconvert || disable_fm) ? 1 : 0;
 	if (fm_debug)
 		ubi_enable_dbg_chk_fastmap(ubi);
diff --git a/drivers/mtd/ubi/fastmap-wl.c b/drivers/mtd/ubi/fastmap-wl.c
index 03c1f1016c0a..2a9cc9413c42 100644
--- a/drivers/mtd/ubi/fastmap-wl.c
+++ b/drivers/mtd/ubi/fastmap-wl.c
@@ -118,7 +118,7 @@ static void wait_free_pebs_for_pool(struct ubi_device *ubi)
 	 * 4. beb_rsvd_pebs: This value should be get under lock ubi->wl_lock
 	 */
 	int reserved = WL_RESERVED_PEBS + EBA_RESERVED_PEBS +
-		       ubi->fm_size / ubi->leb_size - 1;
+		       ubi->fm_size / ubi->leb_size - 1 + ubi->fm_pool_rsv_cnt;
 
 	do {
 		spin_lock(&ubi->wl_lock);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 423f66c91b1d..6e20a0fee72f 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -494,6 +494,7 @@ struct ubi_debug_info {
  * @fast_attach: non-zero if UBI was attached by fastmap
  * @fm_anchor: The next anchor PEB to use for fastmap
  * @fm_do_produce_anchor: If true produce an anchor PEB in wl
+ * @fm_pool_rsv_cnt: Number of reserved PEBs for filling pool/wl_pool
  *
  * @used: RB-tree of used physical eraseblocks
  * @erroneous: RB-tree of erroneous used physical eraseblocks
@@ -604,6 +605,7 @@ struct ubi_device {
 	int fast_attach;
 	struct ubi_wl_entry *fm_anchor;
 	int fm_do_produce_anchor;
+	int fm_pool_rsv_cnt;
 
 	/* Wear-leveling sub-system's stuff */
 	struct rb_root used;
diff --git a/drivers/mtd/ubi/wl.h b/drivers/mtd/ubi/wl.h
index 5ebe374a08ae..7b6715ef6d4a 100644
--- a/drivers/mtd/ubi/wl.h
+++ b/drivers/mtd/ubi/wl.h
@@ -10,8 +10,10 @@ static bool need_wear_leveling(struct ubi_device *ubi);
 static void ubi_fastmap_close(struct ubi_device *ubi);
 static inline void ubi_fastmap_init(struct ubi_device *ubi, int *count)
 {
-	/* Reserve enough LEBs to store two fastmaps. */
-	*count += (ubi->fm_size / ubi->leb_size) * 2;
+	if (ubi->fm_disabled)
+		ubi->fm_pool_rsv_cnt = 0;
+	/* Reserve enough LEBs to store two fastmaps and to fill pools. */
+	*count += (ubi->fm_size / ubi->leb_size) * 2 + ubi->fm_pool_rsv_cnt;
 	INIT_WORK(&ubi->fm_work, update_fastmap_work_fn);
 }
 static struct ubi_wl_entry *may_reserve_for_fm(struct ubi_device *ubi,
-- 
2.39.2


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[PATCH v2 11/12] ubi: fastmap: Add module parameter to control reserving filling pool PEBs

[Zhihao Cheng]

Adding 6th module parameter in 'mtd=xxx' to control whether or not
reserving PEBs for filling pool/wl_pool.

Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/build.c | 26 ++++++++++++++++++++++----
 drivers/mtd/ubi/cdev.c  |  3 ++-
 drivers/mtd/ubi/ubi.h   |  2 +-
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 66d7b6a16aad..7d4ff1193db6 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -35,7 +35,7 @@
 #define MTD_PARAM_LEN_MAX 64
 
 /* Maximum number of comma-separated items in the 'mtd=' parameter */
-#define MTD_PARAM_MAX_COUNT 5
+#define MTD_PARAM_MAX_COUNT 6
 
 /* Maximum value for the number of bad PEBs per 1024 PEBs */
 #define MAX_MTD_UBI_BEB_LIMIT 768
@@ -54,6 +54,7 @@
  * @vid_hdr_offs: VID header offset
  * @max_beb_per1024: maximum expected number of bad PEBs per 1024 PEBs
  * @enable_fm: enable fastmap when value is non-zero
+ * @need_resv_pool: reserve pool->max_size pebs when value is none-zero
  */
 struct mtd_dev_param {
 	char name[MTD_PARAM_LEN_MAX];
@@ -61,6 +62,7 @@ struct mtd_dev_param {
 	int vid_hdr_offs;
 	int max_beb_per1024;
 	int enable_fm;
+	int need_resv_pool;
 };
 
 /* Numbers of elements set in the @mtd_dev_param array */
@@ -825,6 +827,7 @@ static int autoresize(struct ubi_device *ubi, int vol_id)
  * @vid_hdr_offset: VID header offset
  * @max_beb_per1024: maximum expected number of bad PEB per 1024 PEBs
  * @disable_fm: whether disable fastmap
+ * @need_resv_pool: whether reserve pebs to fill fm_pool
  *
  * This function attaches MTD device @mtd_dev to UBI and assign @ubi_num number
  * to the newly created UBI device, unless @ubi_num is %UBI_DEV_NUM_AUTO, in
@@ -840,7 +843,8 @@ static int autoresize(struct ubi_device *ubi, int vol_id)
  * @ubi_devices_mutex.
  */
 int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
-		       int vid_hdr_offset, int max_beb_per1024, bool disable_fm)
+		       int vid_hdr_offset, int max_beb_per1024, bool disable_fm,
+		       bool need_resv_pool)
 {
 	struct ubi_device *ubi;
 	int i, err;
@@ -951,7 +955,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 		UBI_FM_MIN_POOL_SIZE);
 
 	ubi->fm_wl_pool.max_size = ubi->fm_pool.max_size / 2;
-	ubi->fm_pool_rsv_cnt = ubi->fm_pool.max_size;
+	ubi->fm_pool_rsv_cnt = need_resv_pool ? ubi->fm_pool.max_size : 0;
 	ubi->fm_disabled = (!fm_autoconvert || disable_fm) ? 1 : 0;
 	if (fm_debug)
 		ubi_enable_dbg_chk_fastmap(ubi);
@@ -1274,7 +1278,8 @@ static int __init ubi_init(void)
 		mutex_lock(&ubi_devices_mutex);
 		err = ubi_attach_mtd_dev(mtd, p->ubi_num,
 					 p->vid_hdr_offs, p->max_beb_per1024,
-					 p->enable_fm == 0);
+					 p->enable_fm == 0,
+					 p->need_resv_pool != 0);
 		mutex_unlock(&ubi_devices_mutex);
 		if (err < 0) {
 			pr_err("UBI error: cannot attach mtd%d\n",
@@ -1483,6 +1488,18 @@ static int ubi_mtd_param_parse(const char *val, const struct kernel_param *kp)
 	} else
 		p->enable_fm = 0;
 
+	token = tokens[5];
+	if (token) {
+		int err = kstrtoint(token, 10, &p->need_resv_pool);
+
+		if (err) {
+			pr_err("UBI error: bad value for need_resv_pool parameter: %s\n",
+				token);
+			return -EINVAL;
+		}
+	} else
+		p->need_resv_pool = 0;
+
 	mtd_devs += 1;
 	return 0;
 }
@@ -1496,6 +1513,7 @@ MODULE_PARM_DESC(mtd, "MTD devices to attach. Parameter format: mtd=<name|num|pa
 		      __stringify(CONFIG_MTD_UBI_BEB_LIMIT) ") if 0)\n"
 		      "Optional \"ubi_num\" parameter specifies UBI device number which have to be assigned to the newly created UBI device (assigned automatically by default)\n"
 		      "Optional \"enable_fm\" parameter determines whether to enable fastmap during attach. If the value is non-zero, fastmap is enabled. Default value is 0.\n"
+		      "Optional \"need_resv_pool\" parameter determines whether to reserve pool->max_size pebs during attach. If the value is non-zero, peb reservation is enabled. Default value is 0.\n"
 		      "\n"
 		      "Example 1: mtd=/dev/mtd0 - attach MTD device /dev/mtd0.\n"
 		      "Example 2: mtd=content,1984 mtd=4 - attach MTD device with name \"content\" using VID header offset 1984, and MTD device number 4 with default VID header offset.\n"
diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index f43430b9c1e6..98aa00344b29 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -1041,7 +1041,8 @@ static long ctrl_cdev_ioctl(struct file *file, unsigned int cmd,
 		 */
 		mutex_lock(&ubi_devices_mutex);
 		err = ubi_attach_mtd_dev(mtd, req.ubi_num, req.vid_hdr_offset,
-					 req.max_beb_per1024, !!req.disable_fm);
+					 req.max_beb_per1024, !!req.disable_fm,
+					 false);
 		mutex_unlock(&ubi_devices_mutex);
 		if (err < 0)
 			put_mtd_device(mtd);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 6e20a0fee72f..a5ec566df0d7 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -944,7 +944,7 @@ int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
 /* build.c */
 int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 		       int vid_hdr_offset, int max_beb_per1024,
-		       bool disable_fm);
+		       bool disable_fm, bool need_resv_pool);
 int ubi_detach_mtd_dev(int ubi_num, int anyway);
 struct ubi_device *ubi_get_device(int ubi_num);
 void ubi_put_device(struct ubi_device *ubi);
-- 
2.39.2


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[PATCH v2 12/12] ubi: fastmap: Add control in 'UBI_IOCATT' ioctl to reserve PEBs for filling pools

[Zhihao Cheng]

This patch imports a new field 'need_resv_pool' in struct 'ubi_attach_req'
to control whether or not reserving free PEBs for filling pool/wl_pool.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
---
 drivers/mtd/ubi/cdev.c      | 2 +-
 include/uapi/mtd/ubi-user.h | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index 98aa00344b29..0d8f04cf03c5 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -1042,7 +1042,7 @@ static long ctrl_cdev_ioctl(struct file *file, unsigned int cmd,
 		mutex_lock(&ubi_devices_mutex);
 		err = ubi_attach_mtd_dev(mtd, req.ubi_num, req.vid_hdr_offset,
 					 req.max_beb_per1024, !!req.disable_fm,
-					 false);
+					 !!req.need_resv_pool);
 		mutex_unlock(&ubi_devices_mutex);
 		if (err < 0)
 			put_mtd_device(mtd);
diff --git a/include/uapi/mtd/ubi-user.h b/include/uapi/mtd/ubi-user.h
index dcb179de4358..e1571603175e 100644
--- a/include/uapi/mtd/ubi-user.h
+++ b/include/uapi/mtd/ubi-user.h
@@ -248,6 +248,7 @@ enum {
  * @max_beb_per1024: maximum expected number of bad PEB per 1024 PEBs
  * @padding: reserved for future, not used, has to be zeroed
  * @disable_fm: whether disable fastmap
+ * @need_resv_pool: whether reserve free pebs for filling pool/wl_pool
  *
  * This data structure is used to specify MTD device UBI has to attach and the
  * parameters it has to use. The number which should be assigned to the new UBI
@@ -293,7 +294,8 @@ struct ubi_attach_req {
 	__s32 vid_hdr_offset;
 	__s16 max_beb_per1024;
 	__s8 disable_fm;
-	__s8 padding[9];
+	__s8 need_resv_pool;
+	__s8 padding[8];
 };
 
 /*
-- 
2.39.2


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Re: [PATCH v2 00/12] ubi: fastmap: Fix a series of wear leveling problems

[Zhihao Cheng]

在 2023/8/28 14:38, Zhihao Cheng 写道:
> This series of patches fix three problems:
> 1. Inconsistent erase counter from wl entry and disk, for patches 1~4.
> 2. Same PEB is always resued for fastmap data, for patches 5~9.
> 3. First 64 PEBs have large erase counter than others, for patches 10~12.
> 
> Besides, patches 4/5 bring an improvement of the UBI service life.
> 
> Regression tests are in [Link].
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787.
> 
> v1->v2:
>    Patch 6: Change wait condition in wait_free_pebs_for_pool(), there are
> 	   two situations that cause waiting infinately:
> 	   1. __erase_worker schedules itself if -EBUSY returned when
> 	      shutting down system.
> 	   2. The 'min_expect_free' cannot be satisfied when bad block
> 	      occurs and ubi becomes ro(The erased PEB should be the
>                last one of 'min_expect_free', but it becomes bad in
> 	      __erase_worker).
>   PS: After re-testing, the testing results in [Link] is not affected.
> 

Hi, Richard. I hope you can take some time(when you have free time) to 
have a glance of this series of patches, I have made some tests on 
virtual machine for 2+ months(and half month for physical nand flash), 
so far ubi works fine with patches applied.

> 
> Zhihao Cheng (12):
>    ubi: fastmap: Fix missed ec updating after erasing old fastmap data
>      block
>    ubi: fastmap: erase_block: Get erase counter from wl_entry rather than
>      flash
>    ubi: fastmap: Allocate memory with GFP_NOFS in ubi_update_fastmap
>    ubi: Replace erase_block() with sync_erase()
>    ubi: fastmap: Use free pebs reserved for bad block handling
>    ubi: fastmap: Wait until there are enough free PEBs before filling
>      pools
>    ubi: fastmap: Remove unneeded break condition while filling pools
>    ubi: fastmap: may_reserve_for_fm: Don't reserve PEB if fm_anchor
>      exists
>    ubi: fastmap: Get wl PEB even ec beyonds the 'max' if free PEBs are
>      run out
>    ubi: fastmap: Fix lapsed wear leveling for first 64 PEBs
>    ubi: fastmap: Add module parameter to control reserving filling pool
>      PEBs
>    ubi: fastmap: Add control in 'UBI_IOCATT' ioctl to reserve PEBs for
>      filling pools
> 
>   drivers/mtd/ubi/build.c      |  25 +++++++-
>   drivers/mtd/ubi/cdev.c       |   3 +-
>   drivers/mtd/ubi/eba.c        |   3 -
>   drivers/mtd/ubi/fastmap-wl.c | 112 +++++++++++++++++++++++++++--------
>   drivers/mtd/ubi/fastmap.c    |  66 +++------------------
>   drivers/mtd/ubi/ubi.h        |  10 +++-
>   drivers/mtd/ubi/wl.c         |  48 +++++++++------
>   drivers/mtd/ubi/wl.h         |   6 +-
>   include/uapi/mtd/ubi-user.h  |   4 +-
>   9 files changed, 164 insertions(+), 113 deletions(-)
> 


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Re: [PATCH v2 00/12] ubi: fastmap: Fix a series of wear leveling problems

[Richard Weinberger]

----- Ursprüngliche Mail -----
> Von: "chengzhihao1" <chengzhihao1@huawei.com>
> An: "richard" <richard@nod.at>, "Miquel Raynal" <miquel.raynal@bootlin.com>, "Vignesh Raghavendra" <vigneshr@ti.com>,
> "mcoquelin stm32" <mcoquelin.stm32@gmail.com>, "alexandre torgue" <alexandre.torgue@foss.st.com>
> CC: "linux-mtd" <linux-mtd@lists.infradead.org>, "linux-stm32" <linux-stm32@st-md-mailman.stormreply.com>,
> "linux-arm-kernel" <linux-arm-kernel@lists.infradead.org>, "Bagas Sanjaya" <bagasdotme@gmail.com>
> Gesendet: Donnerstag, 12. Oktober 2023 04:57:52
> Betreff: Re: [PATCH v2 00/12] ubi: fastmap: Fix a series of wear leveling problems

> 在 2023/8/28 14:38, Zhihao Cheng 写道:
>> This series of patches fix three problems:
>> 1. Inconsistent erase counter from wl entry and disk, for patches 1~4.
>> 2. Same PEB is always resued for fastmap data, for patches 5~9.
>> 3. First 64 PEBs have large erase counter than others, for patches 10~12.
>> 
>> Besides, patches 4/5 bring an improvement of the UBI service life.
>> 
>> Regression tests are in [Link].
>> 
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=217787.
>> 
>> v1->v2:
>>    Patch 6: Change wait condition in wait_free_pebs_for_pool(), there are
>> 	   two situations that cause waiting infinately:
>> 	   1. __erase_worker schedules itself if -EBUSY returned when
>> 	      shutting down system.
>> 	   2. The 'min_expect_free' cannot be satisfied when bad block
>> 	      occurs and ubi becomes ro(The erased PEB should be the
>>                last one of 'min_expect_free', but it becomes bad in
>> 	      __erase_worker).
>>   PS: After re-testing, the testing results in [Link] is not affected.
>> 
> 
> Hi, Richard. I hope you can take some time(when you have free time) to
> have a glance of this series of patches, I have made some tests on
> virtual machine for 2+ months(and half month for physical nand flash),
> so far ubi works fine with patches applied.

I didn't forget. :-)

Thanks,
//richard

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