Btrfs: implement inode_operations callback tmpfile

This implements the tmpfile callback of struct inode_operations, introduced
in the linux kernel 3.11, and implemented already by some filesystems. This
callback is invoked by the VFS when the flag O_TMPFILE is passed to the open
system call.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>
Reviewed-by: David Sterba <dsterba@suse.cz>

1 files changed, 98 insertions, 20 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 24dfa27a4f76..5c0def8dd761 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5553,6 +5553,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
         struct btrfs_inode_ref *ref;
         struct btrfs_key key[2];
         u32 sizes[2];
+        int nitems = name ? 2 : 1;
         unsigned long ptr;
         int ret;
 
@@ -5572,7 +5573,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
          */
         inode->i_ino = objectid;
 
-        if (dir) {
+        if (dir && name) {
                 trace_btrfs_inode_request(dir);
 
                 ret = btrfs_set_inode_index(dir, index);
@@ -5581,6 +5582,8 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                         iput(inode);
                         return ERR_PTR(ret);
                 }
+        } else if (dir) {
+                *index = 0;
         }
         /*
          * index_cnt is ignored for everything but a dir,
@@ -5605,21 +5608,24 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
         btrfs_set_key_type(&key[0], BTRFS_INODE_ITEM_KEY);
         key[0].offset = 0;
 
-        /*
-         * Start new inodes with an inode_ref. This is slightly more
-         * efficient for small numbers of hard links since they will
-         * be packed into one item. Extended refs will kick in if we
-         * add more hard links than can fit in the ref item.
-         */
-        key[1].objectid = objectid;
-        btrfs_set_key_type(&key[1], BTRFS_INODE_REF_KEY);
-        key[1].offset = ref_objectid;
-
         sizes[0] = sizeof(struct btrfs_inode_item);
-        sizes[1] = name_len + sizeof(*ref);
+
+        if (name) {
+                /*
+                 * Start new inodes with an inode_ref. This is slightly more
+                 * efficient for small numbers of hard links since they will
+                 * be packed into one item. Extended refs will kick in if we
+                 * add more hard links than can fit in the ref item.
+                 */
+                key[1].objectid = objectid;
+                btrfs_set_key_type(&key[1], BTRFS_INODE_REF_KEY);
+                key[1].offset = ref_objectid;
+
+                sizes[1] = name_len + sizeof(*ref);
+        }
 
         path->leave_spinning = 1;
-        ret = btrfs_insert_empty_items(trans, root, path, key, sizes, 2);
+        ret = btrfs_insert_empty_items(trans, root, path, key, sizes, nitems);
         if (ret != 0)
                 goto fail;
 
@@ -5632,12 +5638,14 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                              sizeof(*inode_item));
         fill_inode_item(trans, path->nodes[0], inode_item, inode);
 
-        ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
-                             struct btrfs_inode_ref);
-        btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
-        btrfs_set_inode_ref_index(path->nodes[0], ref, *index);
-        ptr = (unsigned long)(ref + 1);
-        write_extent_buffer(path->nodes[0], name, ptr, name_len);
+        if (name) {
+                ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
+                                     struct btrfs_inode_ref);
+                btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
+                btrfs_set_inode_ref_index(path->nodes[0], ref, *index);
+                ptr = (unsigned long)(ref + 1);
+                write_extent_buffer(path->nodes[0], name, ptr, name_len);
+        }
 
         btrfs_mark_buffer_dirty(path->nodes[0]);
         btrfs_free_path(path);
@@ -5673,7 +5681,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 
         return inode;
 fail:
-        if (dir)
+        if (dir && name)
                 BTRFS_I(dir)->index_cnt--;
         btrfs_free_path(path);
         iput(inode);
@@ -5958,6 +5966,15 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
                 err = btrfs_update_inode(trans, root, inode);
                 if (err)
                         goto fail;
+                if (inode->i_nlink == 1) {
+                        /*
+                         * If new hard link count is 1, it's a file created
+                         * with open(2) O_TMPFILE flag.
+                         */
+                        err = btrfs_orphan_del(trans, inode);
+                        if (err)
+                                goto fail;
+                }
                 d_instantiate(dentry, inode);
                 btrfs_log_new_name(trans, inode, NULL, parent);
         }
@@ -8884,6 +8901,66 @@ static int btrfs_permission(struct inode *inode, int mask)
         return generic_permission(inode, mask);
 }
 
+static int btrfs_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+        struct btrfs_trans_handle *trans;
+        struct btrfs_root *root = BTRFS_I(dir)->root;
+        struct inode *inode = NULL;
+        u64 objectid;
+        u64 index;
+        int ret = 0;
+
+        /*
+         * 5 units required for adding orphan entry
+         */
+        trans = btrfs_start_transaction(root, 5);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
+
+        ret = btrfs_find_free_ino(root, &objectid);
+        if (ret)
+                goto out;
+
+        inode = btrfs_new_inode(trans, root, dir, NULL, 0,
+                                btrfs_ino(dir), objectid, mode, &index);
+        if (IS_ERR(inode)) {
+                ret = PTR_ERR(inode);
+                inode = NULL;
+                goto out;
+        }
+
+        ret = btrfs_init_inode_security(trans, inode, dir, NULL);
+        if (ret)
+                goto out;
+
+        ret = btrfs_update_inode(trans, root, inode);
+        if (ret)
+                goto out;
+
+        inode->i_fop = &btrfs_file_operations;
+        inode->i_op = &btrfs_file_inode_operations;
+
+        inode->i_mapping->a_ops = &btrfs_aops;
+        inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
+        BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
+
+        ret = btrfs_orphan_add(trans, inode);
+        if (ret)
+                goto out;
+
+        d_tmpfile(dentry, inode);
+        mark_inode_dirty(inode);
+
+out:
+        btrfs_end_transaction(trans, root);
+        if (ret)
+                iput(inode);
+        btrfs_balance_delayed_items(root);
+        btrfs_btree_balance_dirty(root);
+
+        return ret;
+}
+
 static const struct inode_operations btrfs_dir_inode_operations = {
         .getattr        = btrfs_getattr,
         .lookup         = btrfs_lookup,
@@ -8904,6 +8981,7 @@ static const struct inode_operations btrfs_dir_inode_operations = {
         .get_acl        = btrfs_get_acl,
         .set_acl        = btrfs_set_acl,
         .update_time    = btrfs_update_time,
+        .tmpfile        = btrfs_tmpfile,
 };
 static const struct inode_operations btrfs_dir_ro_inode_operations = {
         .lookup         = btrfs_lookup,