On 10/02/2022 22:03, Graham Cobb wrote: > On 10/02/2022 21:30, Goldwyn Rodrigues wrote: >> On 19:54 10/02, Graham Cobb wrote: >>> On 10/02/2022 16:51, Goldwyn Rodrigues wrote: >>>> If a read-write root mount is remounted as read-only, the subvolume >>>> is also set to read-only. >>> >>> Errrr... Isn't that exactly what I want? >>> >>> If I have a btrfs filesystem with hundreds of subvols, some of which may >>> be mounted into various places in my filesystem, I would expect that if >>> I remount the main mountpoint as RO, that all the subvols become RO as >>> well. I actually don't mind if the behaviour went further and remounting >>> ANY of the mount points as RO would make them all RO. >>> >>> My mental model is that mounting a subvol somewhere is rather like a >>> bind mount. And a bind mount goes RO if the underlying fs goes RO - >>> doesn't it? >>> >> >> If we want bind mount, we would use bind mount. subvolume mounts and bind >> mounts are different and should be treated as different features. > > Yes that's a good point. However, I am still not convinced that this is > a change in behaviour that is obvious enough to justify the risk of > disruption to existing systems, admin scripts or system managers. > >> >>> Or am I just confused about what this patch is discussing? >> >> Root can also be considered as a unique subvolume with a unique >> subvolume id and a unique name=/ > > But with an important special property that is different from all other > subvolumes: all other subvolumes are reachable from it. I should be a bit clearer. Imagine you create a filesystem and then create two subvolumes within it: a and a/b. You are suggesting that the result of remounting the top level of the filesystem as RO causes different effect on whether subvolume b goes RO depending on whether subvolume a has also been mounted somewhere?
