Btrfs: early fsync support

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/TODO

@@ -7,6 +7,7 @@
 * Get rid of struct ctree_path, limiting tree levels held at one time
 * Add generation number to key pointer in nodes
 * Add parent pointer back to extent map.
+* Implement real list of pending transactions
 * Release
 * Do real tree locking
 * Add extent mirroring (backup copies of blocks)

fs/btrfs/ctree.h

@@ -256,6 +256,7 @@ struct btrfs_fs_info {
 	struct inode *btree_inode;
 	struct mutex trans_mutex;
 	struct mutex fs_mutex;
+	struct list_head trans_list;
 	struct crypto_hash *hash_tfm;
 	spinlock_t hash_lock;
 	struct kobject kobj;

fs/btrfs/disk-io.c

@@ -528,6 +528,7 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 	init_bit_radix(&fs_info->pending_del_radix);
 	INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_NOFS);
 	INIT_RADIX_TREE(&fs_info->dev_radix, GFP_NOFS);
+	INIT_LIST_HEAD(&fs_info->trans_list);
 	sb_set_blocksize(sb, 4096);
 	fs_info->running_transaction = NULL;
 	fs_info->tree_root = tree_root;

fs/btrfs/root-tree.c

@@ -100,7 +100,6 @@ int btrfs_del_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 	BUG_ON(refs == 0);
 	if (refs == 1) {
 		ret = btrfs_del_item(trans, root, path);
-printk("deleting root %Lu %Lu %u\n", key->objectid, key->offset, key->flags);
 	} else {
 		btrfs_set_root_refs(ri, refs - 1);
 printk("ref now %u root %Lu %Lu %u\n", refs -1, key->objectid, key->offset, key->flags);

fs/btrfs/super.c

@@ -11,6 +11,7 @@
 #include <linux/mpage.h>
 #include <linux/swap.h>
 #include <linux/writeback.h>
+#include <linux/statfs.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -932,6 +933,26 @@ out_unlock:
 	return err;
 }
 
+static int btrfs_sync_file(struct file *file,
+			   struct dentry *dentry, int datasync)
+{
+	struct inode *inode = dentry->d_inode;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	int ret;
+	struct btrfs_trans_handle *trans;
+
+	mutex_lock(&root->fs_info->fs_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	if (!trans) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	ret = btrfs_commit_transaction(trans, root);
+	mutex_unlock(&root->fs_info->fs_mutex);
+out:
+	return ret > 0 ? EIO : ret;
+}
+
 static int btrfs_sync_fs(struct super_block *sb, int wait)
 {
 	struct btrfs_trans_handle *trans;
@@ -2353,6 +2374,19 @@ static int btrfs_getattr(struct vfsmount *mnt,
 	return 0;
 }
 
+static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct btrfs_root *root = btrfs_sb(dentry->d_sb);
+	struct btrfs_super_block *disk_super = root->fs_info->disk_super;
+
+	buf->f_namelen = BTRFS_NAME_LEN;
+	buf->f_blocks = btrfs_super_total_blocks(disk_super);
+	buf->f_bfree = buf->f_blocks - btrfs_super_blocks_used(disk_super);
+	buf->f_bavail = buf->f_bfree;
+	buf->f_bsize = dentry->d_sb->s_blocksize;
+	buf->f_type = BTRFS_SUPER_MAGIC;
+	return 0;
+}
 static struct file_system_type btrfs_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "btrfs",
@@ -2362,7 +2396,6 @@ static struct file_system_type btrfs_fs_type = {
 };
 
 static struct super_operations btrfs_super_ops = {
-	.statfs		= simple_statfs,
 	.delete_inode	= btrfs_delete_inode,
 	.put_super	= btrfs_put_super,
 	.read_inode	= btrfs_read_locked_inode,
@@ -2371,6 +2404,7 @@ static struct super_operations btrfs_super_ops = {
 	.write_inode	= btrfs_write_inode,
 	.alloc_inode	= btrfs_alloc_inode,
 	.destroy_inode	= btrfs_destroy_inode,
+	.statfs		= btrfs_statfs,
 };
 
 static struct inode_operations btrfs_dir_inode_operations = {
@@ -2413,6 +2447,7 @@ static struct file_operations btrfs_file_operations = {
 	.mmap		= generic_file_mmap,
 	.open		= generic_file_open,
 	.ioctl		= btrfs_ioctl,
+	.fsync		= btrfs_sync_file,
 };
 
 static int __init init_btrfs_fs(void)

fs/btrfs/transaction.c

@@ -19,6 +19,7 @@ static void put_transaction(struct btrfs_transaction *transaction)
 	if (transaction->use_count == 0) {
 		WARN_ON(total_trans == 0);
 		total_trans--;
+		list_del_init(&transaction->list);
 		memset(transaction, 0, sizeof(*transaction));
 		kmem_cache_free(btrfs_transaction_cachep, transaction);
 	}
@@ -43,6 +44,7 @@ static int join_transaction(struct btrfs_root *root)
 		cur_trans->in_commit = 0;
 		cur_trans->use_count = 1;
 		cur_trans->commit_done = 0;
+		list_add_tail(&cur_trans->list, &root->fs_info->trans_list);
 	}
 	cur_trans->num_writers++;
 	return 0;
@@ -236,6 +238,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 {
 	int ret = 0;
 	struct btrfs_transaction *cur_trans;
+	struct btrfs_transaction *prev_trans = NULL;
 	struct list_head dirty_fs_roots;
 	DEFINE_WAIT(wait);
 
@@ -272,13 +275,29 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	BUG_ON(ret);
 	cur_trans = root->fs_info->running_transaction;
 	root->fs_info->running_transaction = NULL;
-	btrfs_set_super_generation(root->fs_info->disk_super,
-				   root->fs_info->generation + 1);
+	if (cur_trans->list.prev != &root->fs_info->trans_list) {
+		prev_trans = list_entry(cur_trans->list.prev,
+					struct btrfs_transaction, list);
+		if (prev_trans->commit_done)
+			prev_trans = NULL;
+		else
+			prev_trans->use_count++;
+	}
 	mutex_unlock(&root->fs_info->trans_mutex);
+	mutex_unlock(&root->fs_info->fs_mutex);
 	ret = btrfs_write_and_wait_transaction(trans, root);
+	if (prev_trans) {
+		mutex_lock(&root->fs_info->trans_mutex);
+		wait_for_commit(root, prev_trans);
+		put_transaction(prev_trans);
+		mutex_unlock(&root->fs_info->trans_mutex);
+	}
+	btrfs_set_super_generation(root->fs_info->disk_super,
+				   cur_trans->transid);
 	BUG_ON(ret);
-
 	write_ctree_super(trans, root);
+
+	mutex_lock(&root->fs_info->fs_mutex);
 	btrfs_finish_extent_commit(trans, root);
 	mutex_lock(&root->fs_info->trans_mutex);
 	cur_trans->commit_done = 1;

fs/btrfs/transaction.h

@@ -8,6 +8,7 @@ struct btrfs_transaction {
 	int use_count;
 	int commit_done;
 	int magic;
+	struct list_head list;
 	wait_queue_head_t writer_wait;
 	wait_queue_head_t commit_wait;
 };