[PATCH 2/2] f2fs: speed up shrinking extent tree entries

[Jaegeuk Kim]

If there is no candidates for shrinking slab entries, we don't need to traverse
any trees at all.

Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
 fs/f2fs/extent_cache.c | 12 ++++++++++++
 fs/f2fs/f2fs.h         |  1 +
 fs/f2fs/shrinker.c     |  2 +-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 0e97d6af..32693af 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -71,6 +71,8 @@ static struct extent_tree *__grab_extent_tree(struct inode *inode)
 		atomic_set(&et->refcount, 0);
 		et->count = 0;
 		atomic_inc(&sbi->total_ext_tree);
+	} else {
+		atomic_dec(&sbi->total_zombie_tree);
 	}
 	atomic_inc(&et->refcount);
 	up_write(&sbi->extent_tree_lock);
@@ -547,10 +549,14 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
 	unsigned int found;
 	unsigned int node_cnt = 0, tree_cnt = 0;
 	int remained;
+	bool do_free = false;
 
 	if (!test_opt(sbi, EXTENT_CACHE))
 		return 0;
 
+	if (!atomic_read(&sbi->total_zombie_tree))
+		goto free_node;
+
 	if (!down_write_trylock(&sbi->extent_tree_lock))
 		goto out;
 
@@ -580,6 +586,7 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
 	}
 	up_write(&sbi->extent_tree_lock);
 
+free_node:
 	/* 2. remove LRU extent entries */
 	if (!down_write_trylock(&sbi->extent_tree_lock))
 		goto out;
@@ -591,9 +598,13 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
 		if (!remained--)
 			break;
 		list_del_init(&en->list);
+		do_free = true;
 	}
 	spin_unlock(&sbi->extent_lock);
 
+	if (do_free == false)
+		goto unlock_out;
+
 	/*
 	 * reset ino for searching victims from beginning of global extent tree.
 	 */
@@ -651,6 +662,7 @@ void f2fs_destroy_extent_tree(struct inode *inode)
 
 	if (inode->i_nlink && !is_bad_inode(inode) && et->count) {
 		atomic_dec(&et->refcount);
+		atomic_dec(&sbi->total_zombie_tree);
 		return;
 	}
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index a7f6191..90fb970 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -763,6 +763,7 @@ struct f2fs_sb_info {
 	struct list_head extent_list;		/* lru list for shrinker */
 	spinlock_t extent_lock;			/* locking extent lru list */
 	atomic_t total_ext_tree;		/* extent tree count */
+	atomic_t total_zombie_tree;		/* extent zombie tree count */
 	atomic_t total_ext_node;		/* extent info count */
 
 	/* basic filesystem units */
diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
index a11e099..93606f2 100644
--- a/fs/f2fs/shrinker.c
+++ b/fs/f2fs/shrinker.c
@@ -32,7 +32,7 @@ static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
 
 static unsigned long __count_extent_cache(struct f2fs_sb_info *sbi)
 {
-	return atomic_read(&sbi->total_ext_tree) +
+	return atomic_read(&sbi->total_zombie_tree) +
 				atomic_read(&sbi->total_ext_node);
 }
 
-- 
2.5.4 (Apple Git-61)

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