[PATCH] check size of inode backref before adding hardlink

Yan Zheng
2009-08-05T09:13:42Z

For every hardlink in btrfs, there is a corresponding inode back
reference. All inode back references for hardlinks in a given
directory are stored in single b-tree item. The size of b-tree item
is limited by the size of b-tree leaf, so we can only create limited
number of hardlinks to a given file in a directory.

The original code lacks of the check, it oops if the number of
hardlinks goes over the limit. This patch fixes the issue by adding
the check to btrfs_link and btrfs_rename.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

---
diff -urp 1/fs/btrfs/ctree.c 2/fs/btrfs/ctree.c
--- 1/fs/btrfs/ctree.c 2009-07-29 10:03:04.150859426 +0800
+++ 2/fs/btrfs/ctree.c 2009-08-05 14:55:01.850810000 +0800
@@ -2853,6 +2853,12 @@ static noinline int split_leaf(struct bt
int split;
int num_doubles = 0;

+ l = path->nodes[0];
+ slot = path->slots[0];
+ if (extend && data_size + btrfs_item_size_nr(l, slot) +
+ sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root))
+ return -EOVERFLOW;
+
/* first try to make some room by pushing left and right */
if (data_size && ins_key->type != BTRFS_DIR_ITEM_KEY) {
wret = push_leaf_right(trans, root, path, data_size, 0);
diff -urp 1/fs/btrfs/inode.c 2/fs/btrfs/inode.c
--- 1/fs/btrfs/inode.c 2009-07-29 10:03:04.365858071 +0800
+++ 2/fs/btrfs/inode.c 2009-08-05 16:06:24.220810000 +0800
@@ -3674,7 +3674,7 @@ int btrfs_add_link(struct btrfs_trans_ha
struct inode *parent_inode, struct inode *inode,
const char *name, int name_len, int add_backref, u64 index)
{
- int ret;
+ int ret = 0;
struct btrfs_key key;
struct btrfs_root *root = BTRFS_I(parent_inode)->root;

@@ -3682,18 +3682,18 @@ int btrfs_add_link(struct btrfs_trans_ha
btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
key.offset = 0;

- ret = btrfs_insert_dir_item(trans, root, name, name_len,
- parent_inode->i_ino,
- &key, btrfs_inode_type(inode),
- index);
+ if (add_backref) {
+ ret = btrfs_insert_inode_ref(trans, root,
+ name, name_len, inode->i_ino,
+ parent_inode->i_ino, index);
+ }
+
if (ret == 0) {
- if (add_backref) {
- ret = btrfs_insert_inode_ref(trans, root,
- name, name_len,
- inode->i_ino,
- parent_inode->i_ino,
- index);
- }
+ ret = btrfs_insert_dir_item(trans, root, name, name_len,
+ parent_inode->i_ino, &key,
+ btrfs_inode_type(inode), index);
+ BUG_ON(ret);
+
btrfs_i_size_write(parent_inode, parent_inode->i_size +
name_len * 2);
parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
@@ -3877,20 +3877,16 @@ static int btrfs_link(struct dentry *old
atomic_inc(&inode->i_count);

err = btrfs_add_nondir(trans, dentry, inode, 1, index);
-
- if (err)
- drop_inode = 1;
-
- dir->i_sb->s_dirt = 1;
- btrfs_update_inode_block_group(trans, dir);
- err = btrfs_update_inode(trans, root, inode);
-
if (err)
drop_inode = 1;
+ else {
+ dir->i_sb->s_dirt = 1;
+ btrfs_update_inode_block_group(trans, dir);
+ btrfs_update_inode(trans, root, inode);
+ btrfs_log_new_name(trans, inode, NULL, dentry->d_parent);
+ }

nr = trans->blocks_used;
-
- btrfs_log_new_name(trans, inode, NULL, dentry->d_parent);
btrfs_end_transaction_throttle(trans, root);
fail:
if (drop_inode) {
@@ -4833,6 +4829,16 @@ static int btrfs_rename(struct inode *ol

btrfs_set_trans_block_group(trans, new_dir);

+ ret = btrfs_set_inode_index(new_dir, &index);
+ if (ret)
+ goto out_fail;
+
+ ret = btrfs_insert_inode_ref(trans, root, new_dentry->d_name.name,
+ new_dentry->d_name.len, old_inode->i_ino,
+ new_dir->i_ino, index);
+ if (ret)
+ goto out_fail;
+
btrfs_inc_nlink(old_dentry->d_inode);
old_dir->i_ctime = old_dir->i_mtime = ctime;
new_dir->i_ctime = new_dir->i_mtime = ctime;
@@ -4844,8 +4850,7 @@ static int btrfs_rename(struct inode *ol
ret = btrfs_unlink_inode(trans, root, old_dir, old_dentry->d_inode,
old_dentry->d_name.name,
old_dentry->d_name.len);
- if (ret)
- goto out_fail;
+ BUG_ON(ret);

if (new_inode) {
new_inode->i_ctime = CURRENT_TIME;
@@ -4853,24 +4858,17 @@ static int btrfs_rename(struct inode *ol
new_dentry->d_inode,
new_dentry->d_name.name,
new_dentry->d_name.len);
- if (ret)
- goto out_fail;
+ BUG_ON(ret);
if (new_inode->i_nlink == 0) {
ret = btrfs_orphan_add(trans, new_dentry->d_inode);
- if (ret)
- goto out_fail;
+ BUG_ON(ret);
}
-
}
- ret = btrfs_set_inode_index(new_dir, &index);
- if (ret)
- goto out_fail;

ret = btrfs_add_link(trans, new_dentry->d_parent->d_inode,
old_inode, new_dentry->d_name.name,
- new_dentry->d_name.len, 1, index);
- if (ret)
- goto out_fail;
+ new_dentry->d_name.len, 0, index);
+ BUG_ON(ret);

btrfs_log_new_name(trans, old_inode, old_dir,
new_dentry->d_parent);
diff -urp 1/fs/btrfs/inode-item.c 2/fs/btrfs/inode-item.c
--- 1/fs/btrfs/inode-item.c 2009-07-24 09:51:38.372057017 +0800
+++ 2/fs/btrfs/inode-item.c 2009-08-05 15:11:37.141061000 +0800
@@ -149,6 +149,8 @@ int btrfs_insert_inode_ref(struct btrfs_
ptr = (unsigned long)(ref + 1);
ret = 0;
} else if (ret < 0) {
+ if (ret == -EOVERFLOW)
+ ret = -EMLINK;
goto out;
} else {
ref = btrfs_item_ptr(path->nodes[0], path->slots[0],