Btrfs: fix tree logs parallel sync
To improve performance, btrfs_sync_log merges tree log sync
requests. But it wrongly merges sync requests for different
tree logs. If multiple tree logs are synced at the same time,
only one of them actually gets synced.
This patch has following changes to fix the bug:
Move most tree log related fields in btrfs_fs_info to
btrfs_root. This allows merging sync requests separately
for each tree log.
Don't insert root item into the log root tree immediately
after log tree is allocated. Root item for log tree is
inserted when log tree get synced for the first time. This
allows syncing the log root tree without first syncing all
log trees.
At tree-log sync, btrfs_sync_log first sync the log tree;
then updates corresponding root item in the log root tree;
sync the log root tree; then update the super block.
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3cf1725..7feac5a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -849,6 +849,14 @@
spin_lock_init(&root->list_lock);
mutex_init(&root->objectid_mutex);
mutex_init(&root->log_mutex);
+ init_waitqueue_head(&root->log_writer_wait);
+ init_waitqueue_head(&root->log_commit_wait[0]);
+ init_waitqueue_head(&root->log_commit_wait[1]);
+ atomic_set(&root->log_commit[0], 0);
+ atomic_set(&root->log_commit[1], 0);
+ atomic_set(&root->log_writers, 0);
+ root->log_batch = 0;
+ root->log_transid = 0;
extent_io_tree_init(&root->dirty_log_pages,
fs_info->btree_inode->i_mapping, GFP_NOFS);
@@ -933,15 +941,16 @@
return 0;
}
-int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
- struct btrfs_fs_info *fs_info)
+static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
+ struct btrfs_fs_info *fs_info)
{
struct btrfs_root *root;
struct btrfs_root *tree_root = fs_info->tree_root;
+ struct extent_buffer *leaf;
root = kzalloc(sizeof(*root), GFP_NOFS);
if (!root)
- return -ENOMEM;
+ return ERR_PTR(-ENOMEM);
__setup_root(tree_root->nodesize, tree_root->leafsize,
tree_root->sectorsize, tree_root->stripesize,
@@ -950,12 +959,23 @@
root->root_key.objectid = BTRFS_TREE_LOG_OBJECTID;
root->root_key.type = BTRFS_ROOT_ITEM_KEY;
root->root_key.offset = BTRFS_TREE_LOG_OBJECTID;
+ /*
+ * log trees do not get reference counted because they go away
+ * before a real commit is actually done. They do store pointers
+ * to file data extents, and those reference counts still get
+ * updated (along with back refs to the log tree).
+ */
root->ref_cows = 0;
- root->node = btrfs_alloc_free_block(trans, root, root->leafsize,
- 0, BTRFS_TREE_LOG_OBJECTID,
- trans->transid, 0, 0, 0);
+ leaf = btrfs_alloc_free_block(trans, root, root->leafsize,
+ 0, BTRFS_TREE_LOG_OBJECTID,
+ trans->transid, 0, 0, 0);
+ if (IS_ERR(leaf)) {
+ kfree(root);
+ return ERR_CAST(leaf);
+ }
+ root->node = leaf;
btrfs_set_header_nritems(root->node, 0);
btrfs_set_header_level(root->node, 0);
btrfs_set_header_bytenr(root->node, root->node->start);
@@ -967,7 +987,48 @@
BTRFS_FSID_SIZE);
btrfs_mark_buffer_dirty(root->node);
btrfs_tree_unlock(root->node);
- fs_info->log_root_tree = root;
+ return root;
+}
+
+int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
+ struct btrfs_fs_info *fs_info)
+{
+ struct btrfs_root *log_root;
+
+ log_root = alloc_log_tree(trans, fs_info);
+ if (IS_ERR(log_root))
+ return PTR_ERR(log_root);
+ WARN_ON(fs_info->log_root_tree);
+ fs_info->log_root_tree = log_root;
+ return 0;
+}
+
+int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root)
+{
+ struct btrfs_root *log_root;
+ struct btrfs_inode_item *inode_item;
+
+ log_root = alloc_log_tree(trans, root->fs_info);
+ if (IS_ERR(log_root))
+ return PTR_ERR(log_root);
+
+ log_root->last_trans = trans->transid;
+ log_root->root_key.offset = root->root_key.objectid;
+
+ inode_item = &log_root->root_item.inode;
+ inode_item->generation = cpu_to_le64(1);
+ inode_item->size = cpu_to_le64(3);
+ inode_item->nlink = cpu_to_le32(1);
+ inode_item->nbytes = cpu_to_le64(root->leafsize);
+ inode_item->mode = cpu_to_le32(S_IFDIR | 0755);
+
+ btrfs_set_root_bytenr(&log_root->root_item, log_root->node->start);
+ btrfs_set_root_generation(&log_root->root_item, trans->transid);
+
+ WARN_ON(root->log_root);
+ root->log_root = log_root;
+ root->log_transid = 0;
return 0;
}
@@ -1530,10 +1591,6 @@
init_waitqueue_head(&fs_info->transaction_throttle);
init_waitqueue_head(&fs_info->transaction_wait);
init_waitqueue_head(&fs_info->async_submit_wait);
- init_waitqueue_head(&fs_info->tree_log_wait);
- atomic_set(&fs_info->tree_log_commit, 0);
- atomic_set(&fs_info->tree_log_writers, 0);
- fs_info->tree_log_transid = 0;
__setup_root(4096, 4096, 4096, 4096, tree_root,
fs_info, BTRFS_ROOT_TREE_OBJECTID);