Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17]
From: Miklos Szeredi
Date: Mon Feb 24 2020 - 10:28:55 EST
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