Btrfs : compress and nodatacow priority + automation

I have a btrfs partition mounted on / with compression enabled:

mount -o subvol=@,defaults,noatime,nodiratime,compress=zstd,space_cache=v2 /dev/mapper/archlinux /mnt

I want to disable the CoW mecanism on some folders such as: - The folder which contains my VM disks - Any folder that might contain SQLite databases (mostly for browsers) Here's what [btrfs documentation](https://btrfs.readthedocs.io/en/latest/Administration.html#mount-options) states : > If compression is enabled, nodatacow and nodatasum are disabled. But it also states > If nodatacow or nodatasum are enabled, compression is disabled. I'm ok with the fact that they are mutually exclusive, however I do wonder which one will take priority if I set chattr +C to a folder. Will my change remain permanent ? Or will it be overriden during the next boot when my partition is remounted with the compress option ? My guts tell me that chattr +C will take precedence, but I've been unable to find any documentation that would confirm that. Second question is: is there a way to automatically disable CoW on all newly created SQLite databases ? At first I wanted to write a systemd timer which would scan the whole file system to look for SQLite databases and set chattr +C on it. But then in the [chattr man page](https://man7.org/linux/man-pages/man1/chattr.1.html) I read the following: > If it is set on a file which already has data blocks, it is undefined when the blocks assigned to the file will be fully stable. So basically I should not use chattr +C on existing non-empty files. Is there a way to hook into the filesystem so that any file that ends with \.(sqlite|db) or has the SQLite magic bytes won't use CoW ? Or do I have no other choice but to manually create the NoCoW folder before I install the targetted application ? I don't necessarily know if X or Y app is using an SQLite backend, it would be very inconvenient to remove all the app data to set NoCoW every time I realise an app is using SQLite. What would you recommend to somehow automate this process ? EDIT: Do you think it should be distributions maintainers responsibility to set chattr +C during installation of packages that use SQLite ?