[PATCH v5 24/45] dm zoned: dynamically allocate the dm-zoned-meta shrinker

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the dm-zoned-meta shrinker, so that it can be freed
asynchronously via RCU. Then it doesn't need to wait for RCU read-side
critical section when releasing the struct dmz_metadata.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
CC: Alasdair Kergon <agk@xxxxxxxxxx>
CC: Mike Snitzer <snitzer@xxxxxxxxxx>
CC: dm-devel@xxxxxxxxxx
---
 drivers/md/dm-zoned-metadata.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
index 9d3cca8e3dc9..bbb0e69a7908 100644
--- a/drivers/md/dm-zoned-metadata.c
+++ b/drivers/md/dm-zoned-metadata.c
@@ -187,7 +187,7 @@ struct dmz_metadata {
 	struct rb_root		mblk_rbtree;
 	struct list_head	mblk_lru_list;
 	struct list_head	mblk_dirty_list;
-	struct shrinker		mblk_shrinker;
+	struct shrinker		*mblk_shrinker;
 
 	/* Zone allocation management */
 	struct mutex		map_lock;
@@ -615,7 +615,7 @@ static unsigned long dmz_shrink_mblock_cache(struct dmz_metadata *zmd,
 static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink,
 					       struct shrink_control *sc)
 {
-	struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker);
+	struct dmz_metadata *zmd = shrink->private_data;
 
 	return atomic_read(&zmd->nr_mblks);
 }
@@ -626,7 +626,7 @@ static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink,
 static unsigned long dmz_mblock_shrinker_scan(struct shrinker *shrink,
 					      struct shrink_control *sc)
 {
-	struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker);
+	struct dmz_metadata *zmd = shrink->private_data;
 	unsigned long count;
 
 	spin_lock(&zmd->mblk_lock);
@@ -2936,19 +2936,24 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
 	 */
 	zmd->min_nr_mblks = 2 + zmd->nr_map_blocks + zmd->zone_nr_bitmap_blocks * 16;
 	zmd->max_nr_mblks = zmd->min_nr_mblks + 512;
-	zmd->mblk_shrinker.count_objects = dmz_mblock_shrinker_count;
-	zmd->mblk_shrinker.scan_objects = dmz_mblock_shrinker_scan;
-	zmd->mblk_shrinker.seeks = DEFAULT_SEEKS;
 
 	/* Metadata cache shrinker */
-	ret = register_shrinker(&zmd->mblk_shrinker, "dm-zoned-meta:(%u:%u)",
-				MAJOR(dev->bdev->bd_dev),
-				MINOR(dev->bdev->bd_dev));
-	if (ret) {
-		dmz_zmd_err(zmd, "Register metadata cache shrinker failed");
+	zmd->mblk_shrinker = shrinker_alloc(0,  "dm-zoned-meta:(%u:%u)",
+					    MAJOR(dev->bdev->bd_dev),
+					    MINOR(dev->bdev->bd_dev));
+	if (!zmd->mblk_shrinker) {
+		ret = -ENOMEM;
+		dmz_zmd_err(zmd, "Allocate metadata cache shrinker failed");
 		goto err;
 	}
 
+	zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count;
+	zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan;
+	zmd->mblk_shrinker->seeks = DEFAULT_SEEKS;
+	zmd->mblk_shrinker->private_data = zmd;
+
+	shrinker_register(zmd->mblk_shrinker);
+
 	dmz_zmd_info(zmd, "DM-Zoned metadata version %d", zmd->sb_version);
 	for (i = 0; i < zmd->nr_devs; i++)
 		dmz_print_dev(zmd, i);
@@ -2995,7 +3000,7 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
  */
 void dmz_dtr_metadata(struct dmz_metadata *zmd)
 {
-	unregister_shrinker(&zmd->mblk_shrinker);
+	shrinker_free(zmd->mblk_shrinker);
 	dmz_cleanup_metadata(zmd);
 	kfree(zmd);
 }
-- 
2.30.2