Btrfs: introduce the delayed inode ref deletion for the single link inode

The inode reference item is close to inode item, so we insert it simultaneously
with the inode item insertion when we create a file/directory.. In fact, we also
can handle the inode reference deletion by the same way. So we made this patch to
introduce the delayed inode reference deletion for the single link inode(At most
case, the file doesn't has hard link, so we don't take the hard link into account).

This function is based on the delayed inode mechanism. After applying this patch,
we can reduce the time of the file/directory deletion by ~10%.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 99 insertions, 4 deletions

diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 222ca8cdc53a..451b00c86f6c 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1015,6 +1015,18 @@ static void btrfs_release_delayed_inode(struct btrfs_delayed_node *delayed_node)
         }
 }
 
+static void btrfs_release_delayed_iref(struct btrfs_delayed_node *delayed_node)
+{
+        struct btrfs_delayed_root *delayed_root;
+
+        ASSERT(delayed_node->root);
+        clear_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags);
+        delayed_node->count--;
+
+        delayed_root = delayed_node->root->fs_info->delayed_root;
+        finish_one_item(delayed_root);
+}
+
 static int __btrfs_update_delayed_inode(struct btrfs_trans_handle *trans,
                                         struct btrfs_root *root,
                                         struct btrfs_path *path,
@@ -1023,13 +1035,19 @@ static int __btrfs_update_delayed_inode(struct btrfs_trans_handle *trans,
         struct btrfs_key key;
         struct btrfs_inode_item *inode_item;
         struct extent_buffer *leaf;
+        int mod;
         int ret;
 
         key.objectid = node->inode_id;
         btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
         key.offset = 0;
 
-        ret = btrfs_lookup_inode(trans, root, path, &key, 1);
+        if (test_bit(BTRFS_DELAYED_NODE_DEL_IREF, &node->flags))
+                mod = -1;
+        else
+                mod = 1;
+
+        ret = btrfs_lookup_inode(trans, root, path, &key, mod);
         if (ret > 0) {
                 btrfs_release_path(path);
                 return -ENOENT;
@@ -1037,19 +1055,58 @@ static int __btrfs_update_delayed_inode(struct btrfs_trans_handle *trans,
                 return ret;
         }
 
-        btrfs_unlock_up_safe(path, 1);
         leaf = path->nodes[0];
         inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_inode_item);
         write_extent_buffer(leaf, &node->inode_item, (unsigned long)inode_item,
                             sizeof(struct btrfs_inode_item));
         btrfs_mark_buffer_dirty(leaf);
-        btrfs_release_path(path);
 
+        if (!test_bit(BTRFS_DELAYED_NODE_DEL_IREF, &node->flags))
+                goto no_iref;
+
+        path->slots[0]++;
+        if (path->slots[0] >= btrfs_header_nritems(leaf))
+                goto search;
+again:
+        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+        if (key.objectid != node->inode_id)
+                goto out;
+
+        if (key.type != BTRFS_INODE_REF_KEY &&
+            key.type != BTRFS_INODE_EXTREF_KEY)
+                goto out;
+
+        /*
+         * Delayed iref deletion is for the inode who has only one link,
+         * so there is only one iref. The case that several irefs are
+         * in the same item doesn't exist.
+         */
+        btrfs_del_item(trans, root, path);
+out:
+        btrfs_release_delayed_iref(node);
+no_iref:
+        btrfs_release_path(path);
+err_out:
         btrfs_delayed_inode_release_metadata(root, node);
         btrfs_release_delayed_inode(node);
 
-        return 0;
+        return ret;
+
+search:
+        btrfs_release_path(path);
+
+        btrfs_set_key_type(&key, BTRFS_INODE_EXTREF_KEY);
+        key.offset = -1;
+        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+        if (ret < 0)
+                goto err_out;
+        ASSERT(ret);
+
+        ret = 0;
+        leaf = path->nodes[0];
+        path->slots[0]--;
+        goto again;
 }
 
 static inline int btrfs_update_delayed_inode(struct btrfs_trans_handle *trans,
@@ -1793,6 +1850,41 @@ release_node:
         return ret;
 }
 
+int btrfs_delayed_delete_inode_ref(struct inode *inode)
+{
+        struct btrfs_delayed_node *delayed_node;
+
+        delayed_node = btrfs_get_or_create_delayed_node(inode);
+        if (IS_ERR(delayed_node))
+                return PTR_ERR(delayed_node);
+
+        /*
+         * We don't reserve space for inode ref deletion is because:
+         * - We ONLY do async inode ref deletion for the inode who has only
+         *   one link(i_nlink == 1), it means there is only one inode ref.
+         *   And in most case, the inode ref and the inode item are in the
+         *   same leaf, and we will deal with them at the same time.
+         *   Since we are sure we will reserve the space for the inode item,
+         *   it is unnecessary to reserve space for inode ref deletion.
+         * - If the inode ref and the inode item are not in the same leaf,
+         *   We also needn't worry about enospc problem, because we reserve
+         *   much more space for the inode update than it needs.
+         * - At the worst, we can steal some space from the global reservation.
+         *   It is very rare.
+         */
+        mutex_lock(&delayed_node->mutex);
+        if (test_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags))
+                goto release_node;
+
+        set_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags);
+        delayed_node->count++;
+        atomic_inc(&BTRFS_I(inode)->root->fs_info->delayed_root->items);
+release_node:
+        mutex_unlock(&delayed_node->mutex);
+        btrfs_release_delayed_node(delayed_node);
+        return 0;
+}
+
 static void __btrfs_kill_delayed_node(struct btrfs_delayed_node *delayed_node)
 {
         struct btrfs_root *root = delayed_node->root;
@@ -1815,6 +1907,9 @@ static void __btrfs_kill_delayed_node(struct btrfs_delayed_node *delayed_node)
                 btrfs_release_delayed_item(prev_item);
         }
 
+        if (test_bit(BTRFS_DELAYED_NODE_DEL_IREF, &delayed_node->flags))
+                btrfs_release_delayed_iref(delayed_node);
+
         if (test_bit(BTRFS_DELAYED_NODE_INODE_DIRTY, &delayed_node->flags)) {
                 btrfs_delayed_inode_release_metadata(root, delayed_node);
                 btrfs_release_delayed_inode(delayed_node);