On Thu, Jul 02, 2020 at 06:08:21PM +0200, David Sterba wrote: > On Thu, Jul 02, 2020 at 07:56:57AM +0800, Qu Wenruo wrote: > > On 2020/7/2 上午1:39, David Sterba wrote: > > > On Wed, Jul 01, 2020 at 11:25:27AM +0800, Qu Wenruo wrote: > > > Adding the anon_dev argument to btrfs_get_fs_root is wrong and I have > > > never suggested that. What I meant is to put the actual id allocation > > > to the callers where the subvolume is created, ie only 2 places. > > > > You mean to extract btrfs_init_fs_root() out of btrfs_get_fs_root()? > > > > That looks a little risky and I can't find any good solution to make it > > more elegant than the current one. > > I spent more time reading through the get-fs-root functions and the main > problem is that btrfs_get_fs_root is doing several things, and it makes > a lot of code simple, I certainly want to keep it that way. > > The idea was to pre-insert the new root (similar to the root item > insertion, btrfs_insert_root) and not letting btrfs_get_fs_root call to > btrfs_init_fs_info where the anon_bdev allocation happens for all the > other non-ioctl cases. > > Which could be done by factoring out btrfs_init_fs_root from > btrfs_get_fs_root. This would allow to extend only btrfs_init_fs_root > arguments with the anon_bdev, and keep btrfs_get_fs_root intact. > So this is splitting the API from the end. > > What you originally proposed is a split from the begnning, ie. add a > common implementation for existing and new and provide btrfs_get_fs_root > and btrfs_get_new_fs_root that would hide the additional parameters. > > Both ways are IMO valid but I thought it would be easier to pass the > anon bdev inside ioctl callbacks. The problem that makes my proposal > less appealing is that btrfs_read_tree_root gets called earlier than > I'd like so factoring everything after btrfs_init_fs_root would not be > so straightforward. > > In conclusion, your proposal is better and I'm going to merge it. > > > Although I would definitely remove the "__" prefix as we shouldn't add > > such prefix anymore. > > Yeah with the small naming fixups. It's in for-next-20200703. I've updated the changelogs to reflect what we found during debugging the issue, the __ function renamed to btrfs_get_root_ref and some function comments added. All patches reordered and tagged for stable though the preallocation is not within the size limit.
