[PATCH] check size of inode backref before adding hardlink

Yan, Zheng
2009-09-24T09:08:29Z

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
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 2009-09-23 09:55:39.366357021 +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 2009-09-23 05:49:42.007477065 +0800
+++ 2/fs/btrfs/inode.c 2009-09-23 10:20:17.006357143 +0800
@@ -4133,18 +4133,16 @@ static int btrfs_link(struct dentry *old

err = btrfs_add_nondir(trans, dentry, inode, 1, index);

- if (err)
- drop_inode = 1;
-
- btrfs_update_inode_block_group(trans, dir);
- err = btrfs_update_inode(trans, root, inode);
-
- if (err)
+ if (err) {
drop_inode = 1;
+ } else {
+ btrfs_update_inode_block_group(trans, dir);
+ err = btrfs_update_inode(trans, root, inode);
+ BUG_ON(err);
+ 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) {
@@ -5087,23 +5085,26 @@ static int btrfs_rename(struct inode *ol
down_read(&root->fs_info->subvol_sem);

trans = btrfs_start_transaction(root, 1);
+ btrfs_set_trans_block_group(trans, new_dir);

if (dest != root)
btrfs_record_root_in_trans(trans, dest);

- /*
- * make sure the inode gets flushed if it is replacing
- * something.
- */
- if (new_inode && new_inode->i_size &&
- old_inode && S_ISREG(old_inode->i_mode)) {
- btrfs_add_ordered_operation(trans, root, old_inode);
- }
+ ret = btrfs_set_inode_index(new_dir, &index);
+ if (ret)
+ goto out_fail;

- if (old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) {
+ if (unlikely(old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)) {
/* force full log commit if subvolume involved. */
root->fs_info->last_trans_log_full_commit = trans->transid;
} else {
+ ret = btrfs_insert_inode_ref(trans, dest,
+ new_dentry->d_name.name,
+ new_dentry->d_name.len,
+ old_inode->i_ino,
+ new_dir->i_ino, index);
+ if (ret)
+ goto out_fail;
/*
* this is an ugly little race, but the rename is required
* to make sure that if we crash, the inode is either at the
@@ -5113,8 +5114,14 @@ static int btrfs_rename(struct inode *ol
*/
btrfs_pin_log_trans(root);
}
-
- btrfs_set_trans_block_group(trans, new_dir);
+ /*
+ * make sure the inode gets flushed if it is replacing
+ * something.
+ */
+ if (new_inode && new_inode->i_size &&
+ old_inode && S_ISREG(old_inode->i_mode)) {
+ btrfs_add_ordered_operation(trans, root, old_inode);
+ }

old_dir->i_ctime = old_dir->i_mtime = ctime;
new_dir->i_ctime = new_dir->i_mtime = ctime;
@@ -5159,12 +5166,10 @@ static int btrfs_rename(struct inode *ol
BUG_ON(ret);
}
}
- ret = btrfs_set_inode_index(new_dir, &index);
- BUG_ON(ret);

ret = btrfs_add_link(trans, new_dir, old_inode,
new_dentry->d_name.name,
- new_dentry->d_name.len, 1, index);
+ new_dentry->d_name.len, 0, index);
BUG_ON(ret);

if (old_inode->i_ino != BTRFS_FIRST_FREE_OBJECTID) {
@@ -5172,7 +5177,7 @@ static int btrfs_rename(struct inode *ol
new_dentry->d_parent);
btrfs_end_log_trans(root);
}
-
+out_fail:
btrfs_end_transaction_throttle(trans, root);

if (old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
diff -urp 1/fs/btrfs/inode-item.c 2/fs/btrfs/inode-item.c
--- 1/fs/btrfs/inode-item.c 2009-09-23 05:49:41.980477037 +0800
+++ 2/fs/btrfs/inode-item.c 2009-09-23 09:55:56.309353757 +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],