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>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d47ce83..3458b57 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1284,6 +1284,8 @@ struct btrfs_root {
 #define BTRFS_INODE_DIRSYNC            (1 << 10)
 #define BTRFS_INODE_COMPRESS           (1 << 11)
 
+#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:
@@ -2359,6 +2361,8 @@ int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid);
 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,

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5cf3aa7..a272bfd 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1276,8 +1276,10 @@ struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
        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;
 }

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 255c7c5..f9c93a9 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -373,6 +373,10 @@ static noinline int create_subvol(struct btrfs_root *root,
        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);

diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index 29b2d7c..6928bff 100644 (file)
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -473,3 +473,21 @@ 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;
+       }
+}

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index d01cc24..5b158da 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -976,6 +976,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
        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)