On 2016/04/12 3:04, David Sterba wrote:
> The size of root item is more than 400 bytes, which is quite a lot of
> stack space. As we do IO from inside the subvolume ioctls, we should
> keep the stack usage low in case the filesystem is on top of other
> layers (NFS, device mapper, iscsi, etc).
>
> Signed-off-by: David Sterba <dste...@suse.com>
> ---
> fs/btrfs/ioctl.c | 49 ++++++++++++++++++++++++++-----------------------
> 1 file changed, 26 insertions(+), 23 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 053e677839fe..0be13b9c53d9 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -439,7 +439,7 @@ static noinline int create_subvol(struct inode *dir,
> {
> struct btrfs_trans_handle *trans;
> struct btrfs_key key;
> - struct btrfs_root_item root_item;
> + struct btrfs_root_item *root_item;
> struct btrfs_inode_item *inode_item;
> struct extent_buffer *leaf;
> struct btrfs_root *root = BTRFS_I(dir)->root;
> @@ -455,6 +455,10 @@ static noinline int create_subvol(struct inode *dir,
> u64 qgroup_reserved;
> uuid_le new_uuid;
>
> + root_item = kzalloc(sizeof(*root_item), GFP_KERNEL);
> + if (!root_item)
> + return -ENOMEM;
> +
> ret = btrfs_find_free_objectid(root->fs_info->tree_root, &objectid);
> if (ret)
> return ret;
'kfree(root_item)' is necessary here and other 'return'.
Thanks,
Tsutomu
> @@ -509,47 +513,45 @@ static noinline int create_subvol(struct inode *dir,
> BTRFS_UUID_SIZE);
> btrfs_mark_buffer_dirty(leaf);
>
> - memset(&root_item, 0, sizeof(root_item));
> -
> - inode_item = &root_item.inode;
> + inode_item = &root_item->inode;
> btrfs_set_stack_inode_generation(inode_item, 1);
> btrfs_set_stack_inode_size(inode_item, 3);
> btrfs_set_stack_inode_nlink(inode_item, 1);
> btrfs_set_stack_inode_nbytes(inode_item, root->nodesize);
> btrfs_set_stack_inode_mode(inode_item, S_IFDIR | 0755);
>
> - btrfs_set_root_flags(&root_item, 0);
> - btrfs_set_root_limit(&root_item, 0);
> + btrfs_set_root_flags(root_item, 0);
> + btrfs_set_root_limit(root_item, 0);
> btrfs_set_stack_inode_flags(inode_item, 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);
> - btrfs_set_root_refs(&root_item, 1);
> - btrfs_set_root_used(&root_item, leaf->len);
> - btrfs_set_root_last_snapshot(&root_item, 0);
> + btrfs_set_root_bytenr(root_item, leaf->start);
> + btrfs_set_root_generation(root_item, trans->transid);
> + btrfs_set_root_level(root_item, 0);
> + btrfs_set_root_refs(root_item, 1);
> + btrfs_set_root_used(root_item, leaf->len);
> + btrfs_set_root_last_snapshot(root_item, 0);
>
> - btrfs_set_root_generation_v2(&root_item,
> - btrfs_root_generation(&root_item));
> + btrfs_set_root_generation_v2(root_item,
> + btrfs_root_generation(root_item));
> uuid_le_gen(&new_uuid);
> - memcpy(root_item.uuid, new_uuid.b, BTRFS_UUID_SIZE);
> - btrfs_set_stack_timespec_sec(&root_item.otime, cur_time.tv_sec);
> - btrfs_set_stack_timespec_nsec(&root_item.otime, cur_time.tv_nsec);
> - root_item.ctime = root_item.otime;
> - btrfs_set_root_ctransid(&root_item, trans->transid);
> - btrfs_set_root_otransid(&root_item, trans->transid);
> + memcpy(root_item->uuid, new_uuid.b, BTRFS_UUID_SIZE);
> + btrfs_set_stack_timespec_sec(&root_item->otime, cur_time.tv_sec);
> + btrfs_set_stack_timespec_nsec(&root_item->otime, cur_time.tv_nsec);
> + root_item->ctime = root_item->otime;
> + btrfs_set_root_ctransid(root_item, trans->transid);
> + btrfs_set_root_otransid(root_item, trans->transid);
>
> btrfs_tree_unlock(leaf);
> free_extent_buffer(leaf);
> leaf = NULL;
>
> - btrfs_set_root_dirid(&root_item, new_dirid);
> + btrfs_set_root_dirid(root_item, new_dirid);
>
> key.objectid = objectid;
> key.offset = 0;
> key.type = BTRFS_ROOT_ITEM_KEY;
> ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key,
> - &root_item);
> + root_item);
> if (ret)
> goto fail;
>
> @@ -601,12 +603,13 @@ static noinline int create_subvol(struct inode *dir,
> BUG_ON(ret);
>
> ret = btrfs_uuid_tree_add(trans, root->fs_info->uuid_root,
> - root_item.uuid, BTRFS_UUID_KEY_SUBVOL,
> + root_item->uuid, BTRFS_UUID_KEY_SUBVOL,
> objectid);
> if (ret)
> btrfs_abort_transaction(trans, root, ret);
>
> fail:
> + kfree(root_item);
> trans->block_rsv = NULL;
> trans->bytes_reserved = 0;
> btrfs_subvolume_release_metadata(root, &block_rsv, qgroup_reserved);
>
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