[051/105] Btrfs: Fix uninitialized root flags for subvolumes

Greg KH
2011-04-12T14:38:17Z

From: Li Zefan <lizf@cn.fujitsu.com>

commit 08fe4db170b4193603d9d31f40ebaf652d07ac9c upstream.

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>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/btrfs/ctree.h | 4 ++++
fs/btrfs/disk-io.c | 4 +++-
fs/btrfs/ioctl.c | 4 ++++
fs/btrfs/root-tree.c | 18 ++++++++++++++++++
fs/btrfs/transaction.c | 1 +
5 files changed, 30 insertions(+), 1 deletion(-)

--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1284,6 +1284,8 @@ struct btrfs_root {
#define BTRFS_INODE_NOATIME (1 << 9)
#define BTRFS_INODE_DIRSYNC (1 << 10)

+#define BTRFS_INODE_ROOT_ITEM_INIT (1 << 31)
+
/* some macros to generate set/get funcs for the struct fields. This
* assumes there is a lefoo_to_cpu for every type, so lets make a simple
* one for u8:
@@ -2355,6 +2357,8 @@ int btrfs_find_dead_roots(struct btrfs_r
int btrfs_find_orphan_roots(struct btrfs_root *tree_root);
int btrfs_set_root_node(struct btrfs_root_item *item,
struct extent_buffer *node);
+void btrfs_check_and_init_root_item(struct btrfs_root_item *item);
+
/* dir-item.c */
int btrfs_insert_dir_item(struct btrfs_trans_handle *trans,
struct btrfs_root *root, const char *name,
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1184,8 +1184,10 @@ struct btrfs_root *btrfs_read_fs_root_no
root->commit_root = btrfs_root_node(root);
BUG_ON(!root->node);
out:
- if (location->objectid != BTRFS_TREE_LOG_OBJECTID)
+ if (location->objectid != BTRFS_TREE_LOG_OBJECTID) {
root->ref_cows = 1;
+ btrfs_check_and_init_root_item(&root->root_item);
+ }

return root;
}
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -294,6 +294,10 @@ static noinline int create_subvol(struct
inode_item->nbytes = cpu_to_le64(root->leafsize);
inode_item->mode = cpu_to_le32(S_IFDIR | 0755);

+ root_item.flags = 0;
+ root_item.byte_limit = 0;
+ inode_item->flags = cpu_to_le64(BTRFS_INODE_ROOT_ITEM_INIT);
+
btrfs_set_root_bytenr(&root_item, leaf->start);
btrfs_set_root_generation(&root_item, trans->transid);
btrfs_set_root_level(&root_item, 0);
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -471,3 +471,21 @@ again:
btrfs_free_path(path);
return 0;
}
+
+/*
+ * Old btrfs forgets to init root_item->flags and root_item->byte_limit
+ * for subvolumes. 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.
+ */
+void btrfs_check_and_init_root_item(struct btrfs_root_item *root_item)
+{
+ u64 inode_flags = le64_to_cpu(root_item->inode.flags);
+
+ if (!(inode_flags & BTRFS_INODE_ROOT_ITEM_INIT)) {
+ inode_flags |= BTRFS_INODE_ROOT_ITEM_INIT;
+ root_item->inode.flags = cpu_to_le64(inode_flags);
+ root_item->flags = 0;
+ root_item->byte_limit = 0;
+ }
+}
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -970,6 +970,7 @@ static noinline int create_pending_snaps
record_root_in_trans(trans, root);
btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
+ btrfs_check_and_init_root_item(new_root_item);

root_flags = btrfs_root_flags(new_root_item);
if (pending->readonly)