[PATCH v2 0/2] libnvdimm/badrange: simplify code

[PATCH v2 0/2] libnvdimm/badrange: simplify code

[Zhen Lei]

v1 --> v2:
1. Only the titles and descriptions are modified.

v1:
https://lore.kernel.org/patchwork/cover/1292582/	Patch 1-2

Zhen Lei (2):
  libnvdimm/badrange: remove two redundant list_empty() branches
  libnvdimm/badrange: eliminate a meaningless spinlock operation

 drivers/nvdimm/badrange.c | 32 ++++++++------------------------
 1 file changed, 8 insertions(+), 24 deletions(-)

-- 
1.8.3

[PATCH v2 1/2] libnvdimm/badrange: remove two redundant list_empty() branches

[Zhen Lei]

In add_badrange() or badblocks_populate(), the list_empty() branch does
the same things as the code after list_for_each_entry().

The pseudo code is as follows:
1)	if (list_empty()) {
		do things-A
		return Y;
	}

2)	list_for_each_entry()
		do things-B	//can only be entered if !list_empty()

3)	do things-A
        return Y;

It's very clear that, the processing result after deleting 1) is the same
as that before deleting 1).

So delete 1) to simplify code.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 drivers/nvdimm/badrange.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/drivers/nvdimm/badrange.c b/drivers/nvdimm/badrange.c
index b9eeefa27e3a507..9fdba8c43e8605e 100644
--- a/drivers/nvdimm/badrange.c
+++ b/drivers/nvdimm/badrange.c
@@ -53,13 +53,6 @@ static int add_badrange(struct badrange *badrange, u64 addr, u64 length)
 	bre_new = kzalloc(sizeof(*bre_new), GFP_KERNEL);
 	spin_lock(&badrange->lock);
 
-	if (list_empty(&badrange->list)) {
-		if (!bre_new)
-			return -ENOMEM;
-		append_badrange_entry(badrange, bre_new, addr, length);
-		return 0;
-	}
-
 	/*
 	 * There is a chance this is a duplicate, check for those first.
 	 * This will be the common case as ARS_STATUS returns all known
@@ -215,9 +208,6 @@ static void badblocks_populate(struct badrange *badrange,
 {
 	struct badrange_entry *bre;
 
-	if (list_empty(&badrange->list))
-		return;
-
 	list_for_each_entry(bre, &badrange->list, list) {
 		u64 bre_end = bre->start + bre->length - 1;
 
-- 
1.8.3

[PATCH v2 2/2] libnvdimm/badrange: eliminate a meaningless spinlock operation

[Zhen Lei]

badrange_add() take the lock "badrange->lock", but it's released
immediately in add_badrange(), protect nothing.

The pseudo code is as follows:
In badrange_add():
	spin_lock(&badrange->lock);	<---------------
	rc = add_badrange(badrange, addr, length);	|
In add_badrange():					|
	//do nothing					|
	spin_unlock(&badrange->lock);	<---------------
	bre_new = kzalloc(sizeof(*bre_new), GFP_KERNEL);
	spin_lock(&badrange->lock);	<--- lock again

This lock/unlock operation is meaningless.

Because the static function add_badrange() is only called by
badrange_add(), so move its content into badrange_add() then delete it.
By the way, move "kfree(bre_new)" out of the lock protection, it really
doesn't need.

Fixes: b3b454f694db ("libnvdimm: fix clear poison locking with spinlock ...")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 drivers/nvdimm/badrange.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/nvdimm/badrange.c b/drivers/nvdimm/badrange.c
index 9fdba8c43e8605e..7f78b659057902d 100644
--- a/drivers/nvdimm/badrange.c
+++ b/drivers/nvdimm/badrange.c
@@ -45,12 +45,12 @@ static int alloc_and_append_badrange_entry(struct badrange *badrange,
 	return 0;
 }
 
-static int add_badrange(struct badrange *badrange, u64 addr, u64 length)
+int badrange_add(struct badrange *badrange, u64 addr, u64 length)
 {
 	struct badrange_entry *bre, *bre_new;
 
-	spin_unlock(&badrange->lock);
 	bre_new = kzalloc(sizeof(*bre_new), GFP_KERNEL);
+
 	spin_lock(&badrange->lock);
 
 	/*
@@ -63,6 +63,7 @@ static int add_badrange(struct badrange *badrange, u64 addr, u64 length)
 			/* If length has changed, update this list entry */
 			if (bre->length != length)
 				bre->length = length;
+			spin_unlock(&badrange->lock);
 			kfree(bre_new);
 			return 0;
 		}
@@ -72,22 +73,15 @@ static int add_badrange(struct badrange *badrange, u64 addr, u64 length)
 	 * as any overlapping ranges will get resolved when the list is consumed
 	 * and converted to badblocks
 	 */
-	if (!bre_new)
+	if (!bre_new) {
+		spin_unlock(&badrange->lock);
 		return -ENOMEM;
-	append_badrange_entry(badrange, bre_new, addr, length);
-
-	return 0;
-}
-
-int badrange_add(struct badrange *badrange, u64 addr, u64 length)
-{
-	int rc;
+	}
 
-	spin_lock(&badrange->lock);
-	rc = add_badrange(badrange, addr, length);
+	append_badrange_entry(badrange, bre_new, addr, length);
 	spin_unlock(&badrange->lock);
 
-	return rc;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(badrange_add);
 
-- 
1.8.3