Btrfs: Fix uninitialized root flags for subvolumes
root_item->flags and root_item->byte_limit are not initialized when a subvolume is created. This bug is not revealed until we added readonly snapshot support - now you mount a btrfs filesystem and you may find the subvolumes in it are readonly. To work around this problem, we steal a bit from root_item->inode_item->flags, and use it to indicate if those fields have been properly initialized. When we read a tree root from disk, we check if the bit is set, and if not we'll set the flag and initialize the two fields of the root item. Reported-by: Andreas Philipp <philipp.andreas@gmail.com> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Tested-by: Andreas Philipp <philipp.andreas@gmail.com> cc: stable@kernel.org Signed-off-by: Chris Mason <chris.mason@oracle.com>
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5 changed files with 30 additions and 1 deletions
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@ -1284,6 +1284,8 @@ struct btrfs_root {
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#define BTRFS_INODE_DIRSYNC (1 << 10)
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#define BTRFS_INODE_COMPRESS (1 << 11)
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#define BTRFS_INODE_ROOT_ITEM_INIT (1 << 31)
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/* some macros to generate set/get funcs for the struct fields. This
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* assumes there is a lefoo_to_cpu for every type, so lets make a simple
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* one for u8:
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@ -2359,6 +2361,8 @@ int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid);
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int btrfs_find_orphan_roots(struct btrfs_root *tree_root);
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int btrfs_set_root_node(struct btrfs_root_item *item,
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struct extent_buffer *node);
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void btrfs_check_and_init_root_item(struct btrfs_root_item *item);
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/* dir-item.c */
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int btrfs_insert_dir_item(struct btrfs_trans_handle *trans,
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struct btrfs_root *root, const char *name,
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@ -1276,8 +1276,10 @@ struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
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root->commit_root = btrfs_root_node(root);
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BUG_ON(!root->node);
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out:
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if (location->objectid != BTRFS_TREE_LOG_OBJECTID)
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if (location->objectid != BTRFS_TREE_LOG_OBJECTID) {
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root->ref_cows = 1;
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btrfs_check_and_init_root_item(&root->root_item);
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}
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return root;
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}
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@ -373,6 +373,10 @@ static noinline int create_subvol(struct btrfs_root *root,
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inode_item->nbytes = cpu_to_le64(root->leafsize);
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inode_item->mode = cpu_to_le32(S_IFDIR | 0755);
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root_item.flags = 0;
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root_item.byte_limit = 0;
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inode_item->flags = cpu_to_le64(BTRFS_INODE_ROOT_ITEM_INIT);
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btrfs_set_root_bytenr(&root_item, leaf->start);
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btrfs_set_root_generation(&root_item, trans->transid);
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btrfs_set_root_level(&root_item, 0);
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@ -473,3 +473,21 @@ again:
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btrfs_free_path(path);
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return 0;
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}
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/*
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* Old btrfs forgets to init root_item->flags and root_item->byte_limit
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* for subvolumes. To work around this problem, we steal a bit from
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* root_item->inode_item->flags, and use it to indicate if those fields
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* have been properly initialized.
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*/
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void btrfs_check_and_init_root_item(struct btrfs_root_item *root_item)
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{
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u64 inode_flags = le64_to_cpu(root_item->inode.flags);
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if (!(inode_flags & BTRFS_INODE_ROOT_ITEM_INIT)) {
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inode_flags |= BTRFS_INODE_ROOT_ITEM_INIT;
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root_item->inode.flags = cpu_to_le64(inode_flags);
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root_item->flags = 0;
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root_item->byte_limit = 0;
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}
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}
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@ -976,6 +976,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
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record_root_in_trans(trans, root);
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btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
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memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
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btrfs_check_and_init_root_item(new_root_item);
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root_flags = btrfs_root_flags(new_root_item);
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if (pending->readonly)
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