On Mon, Feb 24, 2020 at 3:55 PM James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > Once it's table driven, certainly a sysfs directory becomes possible. > The problem with ST_DEV is filesystems like btrfs and xfs that may have > multiple devices. For XFS there's always a single sb->s_dev though, that's what st_dev will be set to on all files. Btrfs subvolume is sort of a lightweight superblock, so basically all such st_dev's are aliases of the same master superblock. So lookup of all subvolume st_dev's could result in referencing the same underlying struct super_block (just like /proc/$PID will reference the same underlying task group regardless of which of the task group member's PID is used). Having this info in sysfs would spare us a number of issues that a set of new syscalls would bring. The question is, would that be enough, or is there a reason that sysfs can't be used to present the various filesystem related information that fsinfo is supposed to present? Thanks, Miklos
