1 files changed, 201 insertions, 0 deletions

diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
new file mode 100644
index 000000000000..48b82cd7583c
--- /dev/null
+++ b/fs/btrfs/export.c
@@ -0,0 +1,201 @@
+#include <linux/fs.h>
+#include <linux/types.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "btrfs_inode.h"
+#include "print-tree.h"
+#include "export.h"
+#include "compat.h"
+
+#define BTRFS_FID_SIZE_NON_CONNECTABLE          (offsetof(struct btrfs_fid, parent_objectid)/4)
+#define BTRFS_FID_SIZE_CONNECTABLE              (offsetof(struct btrfs_fid, parent_root_objectid)/4)
+#define BTRFS_FID_SIZE_CONNECTABLE_ROOT         (sizeof(struct btrfs_fid)/4)
+
+static int btrfs_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
+                           int connectable)
+{
+        struct btrfs_fid *fid = (struct btrfs_fid *)fh;
+        struct inode *inode = dentry->d_inode;
+        int len = *max_len;
+        int type;
+
+        if ((len < BTRFS_FID_SIZE_NON_CONNECTABLE) ||
+            (connectable && len < BTRFS_FID_SIZE_CONNECTABLE))
+                return 255;
+
+        len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
+        type = FILEID_BTRFS_WITHOUT_PARENT;
+
+        fid->objectid = BTRFS_I(inode)->location.objectid;
+        fid->root_objectid = BTRFS_I(inode)->root->objectid;
+        fid->gen = inode->i_generation;
+
+        if (connectable && !S_ISDIR(inode->i_mode)) {
+                struct inode *parent;
+                u64 parent_root_id;
+
+                spin_lock(&dentry->d_lock);
+
+                parent = dentry->d_parent->d_inode;
+                fid->parent_objectid = BTRFS_I(parent)->location.objectid;
+                fid->parent_gen = parent->i_generation;
+                parent_root_id = BTRFS_I(parent)->root->objectid;
+
+                spin_unlock(&dentry->d_lock);
+
+                if (parent_root_id != fid->root_objectid) {
+                        fid->parent_root_objectid = parent_root_id;
+                        len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
+                        type = FILEID_BTRFS_WITH_PARENT_ROOT;
+                } else {
+                        len = BTRFS_FID_SIZE_CONNECTABLE;
+                        type = FILEID_BTRFS_WITH_PARENT;
+                }
+        }
+
+        *max_len = len;
+        return type;
+}
+
+static struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
+                                       u64 root_objectid, u32 generation)
+{
+        struct btrfs_root *root;
+        struct inode *inode;
+        struct btrfs_key key;
+
+        key.objectid = root_objectid;
+        btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
+        key.offset = (u64)-1;
+
+        root = btrfs_read_fs_root_no_name(btrfs_sb(sb)->fs_info, &key);
+        if (IS_ERR(root))
+                return ERR_CAST(root);
+
+        key.objectid = objectid;
+        btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
+        key.offset = 0;
+
+        inode = btrfs_iget(sb, &key, root, NULL);
+        if (IS_ERR(inode))
+                return (void *)inode;
+
+        if (generation != inode->i_generation) {
+                iput(inode);
+                return ERR_PTR(-ESTALE);
+        }
+
+        return d_obtain_alias(inode);
+}
+
+static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
+                                         int fh_len, int fh_type)
+{
+        struct btrfs_fid *fid = (struct btrfs_fid *) fh;
+        u64 objectid, root_objectid;
+        u32 generation;
+
+        if (fh_type == FILEID_BTRFS_WITH_PARENT) {
+                if (fh_len !=  BTRFS_FID_SIZE_CONNECTABLE)
+                        return NULL;
+                root_objectid = fid->root_objectid;
+        } else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
+                if (fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT)
+                        return NULL;
+                root_objectid = fid->parent_root_objectid;
+        } else
+                return NULL;
+
+        objectid = fid->parent_objectid;
+        generation = fid->parent_gen;
+
+        return btrfs_get_dentry(sb, objectid, root_objectid, generation);
+}
+
+static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
+                                         int fh_len, int fh_type)
+{
+        struct btrfs_fid *fid = (struct btrfs_fid *) fh;
+        u64 objectid, root_objectid;
+        u32 generation;
+
+        if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
+             fh_len != BTRFS_FID_SIZE_CONNECTABLE) &&
+            (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
+             fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
+            (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
+             fh_len != BTRFS_FID_SIZE_NON_CONNECTABLE))
+                return NULL;
+
+        objectid = fid->objectid;
+        root_objectid = fid->root_objectid;
+        generation = fid->gen;
+
+        return btrfs_get_dentry(sb, objectid, root_objectid, generation);
+}
+
+static struct dentry *btrfs_get_parent(struct dentry *child)
+{
+        struct inode *dir = child->d_inode;
+        struct btrfs_root *root = BTRFS_I(dir)->root;
+        struct btrfs_key key;
+        struct btrfs_path *path;
+        struct extent_buffer *leaf;
+        int slot;
+        u64 objectid;
+        int ret;
+
+        path = btrfs_alloc_path();
+
+        key.objectid = dir->i_ino;
+        btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+        key.offset = (u64)-1;
+
+        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        if (ret < 0) {
+                /* Error */
+                btrfs_free_path(path);
+                return ERR_PTR(ret);
+        }
+        leaf = path->nodes[0];
+        slot = path->slots[0];
+        if (ret) {
+                /* btrfs_search_slot() returns the slot where we'd want to
+                   insert a backref for parent inode #0xFFFFFFFFFFFFFFFF.
+                   The _real_ backref, telling us what the parent inode
+                   _actually_ is, will be in the slot _before_ the one
+                   that btrfs_search_slot() returns. */
+                if (!slot) {
+                        /* Unless there is _no_ key in the tree before... */
+                        btrfs_free_path(path);
+                        return ERR_PTR(-EIO);
+                }
+                slot--;
+        }
+
+        btrfs_item_key_to_cpu(leaf, &key, slot);
+        btrfs_free_path(path);
+
+        if (key.objectid != dir->i_ino || key.type != BTRFS_INODE_REF_KEY)
+                return ERR_PTR(-EINVAL);
+
+        objectid = key.offset;
+
+        /* If we are already at the root of a subvol, return the real root */
+        if (objectid == dir->i_ino)
+                return dget(dir->i_sb->s_root);
+
+        /* Build a new key for the inode item */
+        key.objectid = objectid;
+        btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
+        key.offset = 0;
+
+        return d_obtain_alias(btrfs_iget(root->fs_info->sb, &key, root, NULL));
+}
+
+const struct export_operations btrfs_export_ops = {
+        .encode_fh      = btrfs_encode_fh,
+        .fh_to_dentry   = btrfs_fh_to_dentry,
+        .fh_to_parent   = btrfs_fh_to_parent,
+        .get_parent     = btrfs_get_parent,
+};