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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Damien Le Moal <damien.lemoal@wdc.com>,
        Mike Snitzer <snitzer@redhat.com>
Subject: [PATCH 4.19 276/361] dm zoned: fix metadata block ref counting
Date:   Sun, 11 Nov 2018 14:20:23 -0800
Message-Id: <20181111221655.434696265@linuxfoundation.org>
In-Reply-To: <20181111221619.915519183@linuxfoundation.org>
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4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Damien Le Moal <damien.lemoal@wdc.com>

commit 33c2865f8d011a2ca9f67124ddab9dc89382e9f1 upstream.

Since the ref field of struct dmz_mblock is always used with the
spinlock of struct dmz_metadata locked, there is no need to use an
atomic_t type. Change the type of the ref field to an unsigne
integer.

Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/dm-zoned-metadata.c |   20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

--- a/drivers/md/dm-zoned-metadata.c
+++ b/drivers/md/dm-zoned-metadata.c
@@ -99,7 +99,7 @@ struct dmz_mblock {
 	struct rb_node		node;
 	struct list_head	link;
 	sector_t		no;
-	atomic_t		ref;
+	unsigned int		ref;
 	unsigned long		state;
 	struct page		*page;
 	void			*data;
@@ -296,7 +296,7 @@ static struct dmz_mblock *dmz_alloc_mblo
 
 	RB_CLEAR_NODE(&mblk->node);
 	INIT_LIST_HEAD(&mblk->link);
-	atomic_set(&mblk->ref, 0);
+	mblk->ref = 0;
 	mblk->state = 0;
 	mblk->no = mblk_no;
 	mblk->data = page_address(mblk->page);
@@ -397,7 +397,7 @@ static struct dmz_mblock *dmz_fetch_mblo
 		return NULL;
 
 	spin_lock(&zmd->mblk_lock);
-	atomic_inc(&mblk->ref);
+	mblk->ref++;
 	set_bit(DMZ_META_READING, &mblk->state);
 	dmz_insert_mblock(zmd, mblk);
 	spin_unlock(&zmd->mblk_lock);
@@ -484,7 +484,8 @@ static void dmz_release_mblock(struct dm
 
 	spin_lock(&zmd->mblk_lock);
 
-	if (atomic_dec_and_test(&mblk->ref)) {
+	mblk->ref--;
+	if (mblk->ref == 0) {
 		if (test_bit(DMZ_META_ERROR, &mblk->state)) {
 			rb_erase(&mblk->node, &zmd->mblk_rbtree);
 			dmz_free_mblock(zmd, mblk);
@@ -511,7 +512,8 @@ static struct dmz_mblock *dmz_get_mblock
 	mblk = dmz_lookup_mblock(zmd, mblk_no);
 	if (mblk) {
 		/* Cache hit: remove block from LRU list */
-		if (atomic_inc_return(&mblk->ref) == 1 &&
+		mblk->ref++;
+		if (mblk->ref == 1 &&
 		    !test_bit(DMZ_META_DIRTY, &mblk->state))
 			list_del_init(&mblk->link);
 	}
@@ -753,7 +755,7 @@ int dmz_flush_metadata(struct dmz_metada
 
 		spin_lock(&zmd->mblk_lock);
 		clear_bit(DMZ_META_DIRTY, &mblk->state);
-		if (atomic_read(&mblk->ref) == 0)
+		if (mblk->ref == 0)
 			list_add_tail(&mblk->link, &zmd->mblk_lru_list);
 		spin_unlock(&zmd->mblk_lock);
 	}
@@ -2308,7 +2310,7 @@ static void dmz_cleanup_metadata(struct
 		mblk = list_first_entry(&zmd->mblk_dirty_list,
 					struct dmz_mblock, link);
 		dmz_dev_warn(zmd->dev, "mblock %llu still in dirty list (ref %u)",
-			     (u64)mblk->no, atomic_read(&mblk->ref));
+			     (u64)mblk->no, mblk->ref);
 		list_del_init(&mblk->link);
 		rb_erase(&mblk->node, &zmd->mblk_rbtree);
 		dmz_free_mblock(zmd, mblk);
@@ -2326,8 +2328,8 @@ static void dmz_cleanup_metadata(struct
 	root = &zmd->mblk_rbtree;
 	rbtree_postorder_for_each_entry_safe(mblk, next, root, node) {
 		dmz_dev_warn(zmd->dev, "mblock %llu ref %u still in rbtree",
-			     (u64)mblk->no, atomic_read(&mblk->ref));
-		atomic_set(&mblk->ref, 0);
+			     (u64)mblk->no, mblk->ref);
+		mblk->ref = 0;
 		dmz_free_mblock(zmd, mblk);
 	}