useradd: skip btrfs subvolume creation for system users

[silverhadch]

Gate subvolume creation on user_id >= UID_MIN to exclude system users regardless of their home path.

Fixes: c1d36a8 (2019-05-04; "Add support for btrfs subvolumes for user homes")

[alejandro-colomar]

The code seems good to me.

Do we need to document that BTRFS configuration is ignored for system users?

Also, I think the commit message should document why we don't want BTRFS subvolumes for system users.

[silverhadch]

The code seems good to me.

Do we need to document that BTRFS configuration is ignored for system users?

Also, I think the commit message should document why we don't want BTRFS subvolumes for system users.

Subvolumes for non intercative users are wasteful as they multiply metadata operations and generate unneccesary filesystem objects for operations, a system user who doesnt generate snapshot worthy data, wont use.

But I dont think its worth documenting as this is simply sane design. This BTRFS Backend never mattered to system users as the BTRFS Backend orginally released only supported interactive subvol creation. There is no usage for subvols (aka wasting metadata) for system users with state home dirs.

[alejandro-colomar]

The code seems good to me.
Do we need to document that BTRFS configuration is ignored for system users?
Also, I think the commit message should document why we don't want BTRFS subvolumes for system users.

Subvolumes for non intercative users are wasteful as they multiply metadata operations and generate unneccesary filesystem objects for operations, a system user who doesnt generate snapshot worthy data, wont use.

Please copy this into the commit message.

But I dont think its worth documenting as this is simply sane design. This BTRFS Backend never mattered to system users as the BTRFS Backend orginally released only supported interactive subvol creation. There is no usage for subvols (aka wasting metadata) for system users with state home dirs.

This is still useful information for someone like me that has never used BTRFS and doesn't know anything about it other than the fact that it's a file system. :)

I'd like to have it at least in the commit message. I don't care too much about the manual page.

[silverhadch]

The code seems good to me.
Do we need to document that BTRFS configuration is ignored for system users?
Also, I think the commit message should document why we don't want BTRFS subvolumes for system users.

Subvolumes for non intercative users are wasteful as they multiply metadata operations and generate unneccesary filesystem objects for operations, a system user who doesnt generate snapshot worthy data, wont use.

Please copy this into the commit message.

But I dont think its worth documenting as this is simply sane design. This BTRFS Backend never mattered to system users as the BTRFS Backend orginally released only supported interactive subvol creation. There is no usage for subvols (aka wasting metadata) for system users with state home dirs.

This is still useful information for someone like me that has never used BTRFS and doesn't know anything about it other than the fact that it's a file system. :)

I'd like to have it at least in the commit message. I don't care too much about the manual page.

Done. Documented in the commit message.

[hallyn]

It seems to me this should be optional, no?

I don't think everyone would agree that every user under UID_MIN does not benefit from subvolumes.

[silverhadch]

It seems to me this should be optional, no?

I don't think everyone would agree that every user under UID_MIN does not benefit from subvolumes.

How so?

Why should a System User need to waste resources?

[ikerexxe]

I think this should be optional rather than hardcoded. Following the Unix philosophy of "mechanism, not policy," we should default the behavior to off (no subvolumes for system users). This addresses the performance concerns while providing a configuration toggle for edge cases or environments that still need it.

My two cents

[hallyn]

Yup I'd be fine with making it the default to not create the subvolume for system users.