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authorChris Mason <chris.mason@oracle.com>2008-11-17 21:14:24 -0500
committerChris Mason <chris.mason@oracle.com>2008-11-17 21:14:24 -0500
commitea9e8b11bd1252dcbc23afefcf1a52ec6aa3c113 (patch)
tree3573c8d79e1936e8c921a3be77abda35124e0d78
parent0660b5af3f7ac0fac69de975914e1f4a3a586fb3 (diff)
Btrfs: prevent loops in the directory tree when creating snapshots
For a directory tree: /mnt/subvolA/subvolB btrfsctl -s /mnt/subvolA/subvolB /mnt Will create a directory loop with subvolA under subvolB. This commit uses the forward refs for each subvol and snapshot to error out before creating the loop. Signed-off-by: Chris Mason <chris.mason@oracle.com>
-rw-r--r--fs/btrfs/ctree.h3
-rw-r--r--fs/btrfs/disk-io.c5
-rw-r--r--fs/btrfs/ioctl.c50
-rw-r--r--fs/btrfs/root-tree.c16
4 files changed, 73 insertions, 1 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ad2cbe63503..70b3dbb4de1 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1801,6 +1801,9 @@ int btrfs_drop_subtree(struct btrfs_trans_handle *trans,
struct extent_buffer *node,
struct extent_buffer *parent);
/* root-item.c */
+int btrfs_find_root_ref(struct btrfs_root *tree_root,
+ struct btrfs_path *path,
+ u64 root_id, u64 ref_id);
int btrfs_add_root_ref(struct btrfs_trans_handle *trans,
struct btrfs_root *tree_root,
u64 root_id, u8 type, u64 ref_id,
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8d7866b733d..e18250a6fd2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1129,7 +1129,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
kfree(root);
return ERR_PTR(ret);
}
-
+#if 0
ret = btrfs_sysfs_add_root(root);
if (ret) {
free_extent_buffer(root->node);
@@ -1137,6 +1137,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
kfree(root);
return ERR_PTR(ret);
}
+#endif
root->in_sysfs = 1;
return root;
}
@@ -1963,8 +1964,10 @@ int btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
down_write(&root->anon_super.s_umount);
kill_anon_super(&root->anon_super);
}
+#if 0
if (root->in_sysfs)
btrfs_sysfs_del_root(root);
+#endif
if (root->node)
free_extent_buffer(root->node);
if (root->commit_root)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 536ae883780..8828109fa58 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -284,6 +284,56 @@ static noinline int btrfs_mksubvol(struct path *parent, char *name,
* subvolume with specific mode bits.
*/
if (snap_src) {
+ struct dentry *dir = dentry->d_parent;
+ struct dentry *test = dir->d_parent;
+ struct btrfs_path *path = btrfs_alloc_path();
+ int ret;
+ u64 test_oid;
+ u64 parent_oid = BTRFS_I(dir->d_inode)->root->root_key.objectid;
+
+ test_oid = snap_src->root_key.objectid;
+
+ ret = btrfs_find_root_ref(snap_src->fs_info->tree_root,
+ path, parent_oid, test_oid);
+ if (ret == 0)
+ goto create;
+ btrfs_release_path(snap_src->fs_info->tree_root, path);
+
+ /* we need to make sure we aren't creating a directory loop
+ * by taking a snapshot of something that has our current
+ * subvol in its directory tree. So, this loops through
+ * the dentries and checks the forward refs for each subvolume
+ * to see if is references the subvolume where we are
+ * placing this new snapshot.
+ */
+ while(1) {
+ if (!test ||
+ dir == snap_src->fs_info->sb->s_root ||
+ test == snap_src->fs_info->sb->s_root ||
+ test->d_inode->i_sb != snap_src->fs_info->sb) {
+ break;
+ }
+ if (S_ISLNK(test->d_inode->i_mode)) {
+ printk("Symlink in snapshot path, failed\n");
+ error = -EMLINK;
+ btrfs_free_path(path);
+ goto out_drop_write;
+ }
+ test_oid =
+ BTRFS_I(test->d_inode)->root->root_key.objectid;
+ ret = btrfs_find_root_ref(snap_src->fs_info->tree_root,
+ path, test_oid, parent_oid);
+ if (ret == 0) {
+ printk("Snapshot creation failed, looping\n");
+ error = -EMLINK;
+ btrfs_free_path(path);
+ goto out_drop_write;
+ }
+ btrfs_release_path(snap_src->fs_info->tree_root, path);
+ test = test->d_parent;
+ }
+create:
+ btrfs_free_path(path);
error = create_snapshot(snap_src, dentry, name, namelen);
} else {
error = create_subvol(BTRFS_I(parent->dentry->d_inode)->root,
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index e9be3abcb36..dbe20d4c6ea 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -300,6 +300,22 @@ int btrfs_del_root_ref(struct btrfs_trans_handle *trans,
return ret;
}
+int btrfs_find_root_ref(struct btrfs_root *tree_root,
+ struct btrfs_path *path,
+ u64 root_id, u64 ref_id)
+{
+ struct btrfs_key key;
+ int ret;
+
+ key.objectid = root_id;
+ key.type = BTRFS_ROOT_REF_KEY;
+ key.offset = ref_id;
+
+ ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
+ return ret;
+}
+
+
/*
* add a btrfs_root_ref item. type is either BTRFS_ROOT_REF_KEY
* or BTRFS_ROOT_BACKREF_KEY.