f2fs: introduce zombie list for fast shrinking extent trees

This patch removes refcount, and instead, adds zombie_list to shrink directly
without radix tree traverse.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

2 files changed, 23 insertions, 29 deletions

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index b37184f720e8..4dee2be9a648 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -68,13 +68,13 @@ static struct extent_tree *__grab_extent_tree(struct inode *inode)
                 et->root = RB_ROOT;
                 et->cached_en = NULL;
                 rwlock_init(&et->lock);
-                atomic_set(&et->refcount, 0);
+                INIT_LIST_HEAD(&et->list);
                 et->count = 0;
                 atomic_inc(&sbi->total_ext_tree);
         } else {
                 atomic_dec(&sbi->total_zombie_tree);
+                list_del_init(&et->list);
         }
-        atomic_inc(&et->refcount);
         up_write(&sbi->extent_tree_lock);
 
         /* never died until evict_inode */
@@ -551,9 +551,9 @@ static unsigned int f2fs_update_extent_tree_range(struct inode *inode,
 unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
 {
         struct extent_tree *treevec[EXT_TREE_VEC_SIZE];
+        struct extent_tree *et, *next;
         struct extent_node *en, *tmp;
         unsigned long ino = F2FS_ROOT_INO(sbi);
-        struct radix_tree_root *root = &sbi->extent_tree_root;
         unsigned int found;
         unsigned int node_cnt = 0, tree_cnt = 0;
         int remained;
@@ -569,29 +569,20 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
                 goto out;
 
         /* 1. remove unreferenced extent tree */
-        while ((found = radix_tree_gang_lookup(root,
-                                (void **)treevec, ino, EXT_TREE_VEC_SIZE))) {
-                unsigned i;
-
-                ino = treevec[found - 1]->ino + 1;
-                for (i = 0; i < found; i++) {
-                        struct extent_tree *et = treevec[i];
-
-                        if (!atomic_read(&et->refcount)) {
-                                write_lock(&et->lock);
-                                node_cnt += __free_extent_tree(sbi, et, true);
-                                write_unlock(&et->lock);
+        list_for_each_entry_safe(et, next, &sbi->zombie_list, list) {
+                write_lock(&et->lock);
+                node_cnt += __free_extent_tree(sbi, et, true);
+                write_unlock(&et->lock);
 
-                                radix_tree_delete(root, et->ino);
-                                kmem_cache_free(extent_tree_slab, et);
-                                atomic_dec(&sbi->total_ext_tree);
-                                atomic_dec(&sbi->total_zombie_tree);
-                                tree_cnt++;
+                list_del_init(&et->list);
+                radix_tree_delete(&sbi->extent_tree_root, et->ino);
+                kmem_cache_free(extent_tree_slab, et);
+                atomic_dec(&sbi->total_ext_tree);
+                atomic_dec(&sbi->total_zombie_tree);
+                tree_cnt++;
 
-                                if (node_cnt + tree_cnt >= nr_shrink)
-                                        goto unlock_out;
-                        }
-                }
+                if (node_cnt + tree_cnt >= nr_shrink)
+                        goto unlock_out;
         }
         up_write(&sbi->extent_tree_lock);
 
@@ -619,7 +610,7 @@ free_node:
          */
         ino = F2FS_ROOT_INO(sbi);
 
-        while ((found = radix_tree_gang_lookup(root,
+        while ((found = radix_tree_gang_lookup(&sbi->extent_tree_root,
                                 (void **)treevec, ino, EXT_TREE_VEC_SIZE))) {
                 unsigned i;
 
@@ -670,8 +661,10 @@ void f2fs_destroy_extent_tree(struct inode *inode)
                 return;
 
         if (inode->i_nlink && !is_bad_inode(inode) && et->count) {
-                atomic_dec(&et->refcount);
+                down_write(&sbi->extent_tree_lock);
+                list_add_tail(&et->list, &sbi->zombie_list);
                 atomic_inc(&sbi->total_zombie_tree);
+                up_write(&sbi->extent_tree_lock);
                 return;
         }
 
@@ -680,8 +673,7 @@ void f2fs_destroy_extent_tree(struct inode *inode)
 
         /* delete extent tree entry in radix tree */
         down_write(&sbi->extent_tree_lock);
-        atomic_dec(&et->refcount);
-        f2fs_bug_on(sbi, atomic_read(&et->refcount) || et->count);
+        f2fs_bug_on(sbi, et->count);
         radix_tree_delete(&sbi->extent_tree_root, inode->i_ino);
         kmem_cache_free(extent_tree_slab, et);
         atomic_dec(&sbi->total_ext_tree);
@@ -737,6 +729,7 @@ void init_extent_cache_info(struct f2fs_sb_info *sbi)
         INIT_LIST_HEAD(&sbi->extent_list);
         spin_lock_init(&sbi->extent_lock);
         atomic_set(&sbi->total_ext_tree, 0);
+        INIT_LIST_HEAD(&sbi->zombie_list);
         atomic_set(&sbi->total_zombie_tree, 0);
         atomic_set(&sbi->total_ext_node, 0);
 }
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d81bf5a43714..e2990c978661 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -359,8 +359,8 @@ struct extent_tree {
         struct rb_root root;            /* root of extent info rb-tree */
         struct extent_node *cached_en;  /* recently accessed extent node */
         struct extent_info largest;     /* largested extent info */
+        struct list_head list;          /* to be used by sbi->zombie_list */
         rwlock_t lock;                  /* protect extent info rb-tree */
-        atomic_t refcount;              /* reference count of rb-tree */
         unsigned int count;             /* # of extent node in rb-tree*/
 };
 
@@ -764,6 +764,7 @@ 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 */
+        struct list_head zombie_list;           /* extent zombie tree list */
         atomic_t total_zombie_tree;             /* extent zombie tree count */
         atomic_t total_ext_node;                /* extent info count */