> It seems rather another an incomplete EROFS from several points > of view. Also see: > https://lore.kernel.org/all/1b192a85-e1da-0925-ef26-178b93d0aa45@xxxxxxxxxxxxx/T/#u > Ironically, ZUFS is one of two new filesystems that were discussed in LSFMM19, where the community reactions rhyme with the reactions to composefs. The discussion on Incremental FS resembles composefs case even more [1]. AFAIK, Android is still maintaining Incremental FS out-of-tree. Alexander and Giuseppe, I'd like to join Gao is saying that I think it is in the best interest of everyone, composefs developers and prospect users included, if the composefs requirements would drive improvement to existing kernel subsystems rather than adding a custom filesystem driver that partly duplicates other subsystems. Especially so, when the modifications to existing components (erofs and overlayfs) appear to be relatively minor and the maintainer of erofs is receptive to new features and happy to collaborate with you. w.r.t overlayfs, I am not even sure that anything needs to be modified in the driver. overlayfs already supports "metacopy" feature which means that an upper layer could be composed in a way that the file content would be read from an arbitrary path in lower fs, e.g. objects/cc/XXX. I gave a talk on LPC a few years back about overlayfs and container images [2]. The emphasis was that overlayfs driver supports many new features, but userland tools for building advanced overlayfs images based on those new features are nowhere to be found. I may be wrong, but it looks to me like composefs could potentially fill this void, without having to modify the overlayfs driver at all, or maybe just a little bit. Please start a discussion with overlayfs developers about missing driver features if you have any. Overall, this sounds like a fun discussion to have at LSFMMBPF23 [3] so you are most welcome to submit a topic proposal for "opportunistically sharing verified image filesystem". Thanks, Amir. [1] https://lore.kernel.org/linux-fsdevel/CAK8JDrGRzA+yphpuX+GQ0syRwF_p2Fora+roGCnYqB5E1eOmXA@xxxxxxxxxxxxxx/ [2] https://lpc.events/event/7/contributions/639/attachments/501/969/Overlayfs-containers-lpc-2020.pdf [3] https://lore.kernel.org/linux-fsdevel/Y7hDVliKq+PzY1yY@localhost.localdomain/
