> So I actually don't think project quota as implemented by XFS (and with > which me and Ted want to stay compatible with) isn't different from what you > want. Let me explain what XFS does: > 1) Each file has an additional ID - the project ID > 2) Each dir can have XFS_DIFLAG_PROJINHERIT flag set. When this flag is > set, all files and directories created in the directory inherit project > ID, directories also inherit XFS_DIFLAG_PROJINHERIT - this is > equivalent of sgid bit on directories for gids. > 3) When you hard-link a file into directory with XFS_DIFLAG_PROJINHERIT > set, the file already has to have the same project ID as the directory > you are linking into. > 4) When you rename a file into a directory with XFS_DIFLAG_PROJINHERIT > set, the file already has to have the same project ID as the directory > you are renaming into. > 5) If you call statfs() on a directory with XFS_DIFLAG_PROJINHERIT set > and project quota is being enforced, statfs() will return free/used > blocks of the corresponding project instead of number of free/used > blocks in the filesystem. > > Now if, as an administrator, you decide you need completely generic > additional ID, you can do so. You just never set XFS_DIFLAG_PROJINHERIT. > Quota accounting and enforcement works just fine without that flag. > > So the discussion really is about the semantics of the > XFS_DIFLAG_PROJINHERIT flag. If you want automatic inheritance of project > ids, you set XFS_DIFLAG_PROJINHERIT. With that you'll get additional > limitations described in 3) and 4). And I am of the opinion that these > limitations help to maintain sanity in a system where project quotas are > used. I can imagine XFS_DIFLAG_PROJINHERIT would be split in two flags > for ext4 - one controlling whether project ID is inherited, another > controlling whether we enforce rules 3) and 4) but such difference from XFS > would have to be very well justified because different filesystems having > subtly different semantics is a real administrative nightmare, much worse > than the additional cp + unlink done when rename() returns EXDEV because > you tried to rename from one project to another. Thank you so much for your detailed introduction! I didn't know there is a tunable XFS_DIFLAG_PROJINHERIT flag and I thought that rule 3) and 4) always took effect. I would like to keep everything compatible with XFS if this flag can turn on/off rule 3) and 4) freely. I will check the implement details of XFS in case of making similar mistakes. Regards, Li Xi -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
