Re: [LSF/MM/BPF TOPIC] statx attributes

[Steve French <smfrench@gmail.com>]

> Which API is used in other OS to query the offline bit?
> Do they use SMB specific API, as Windows does?

No it is not smb specific - a local fs can also report this.  It is
included in the attribute bits for files and directories, it also
includes a few additional bits that are used by HSM software on local
drives (e.g. FILE_ATTRIBUTE_PINNED when the file may not be taken
offline by HSM software)
ATTRIBUTE_HIDDEN
ATTRIBUTE_SYSTEM
ATTRIBUTE_DIRECTORY
ATTRIGBUTE_ARCHIVE
ATTRIBUTE_TEMPORARY
ATTRIBUTE_SPARSE_FILE
ATTRIBUTE_REPARE_POINT
ATTRIBUTE_COMPRESSED
ATTRIBUTE_NOT_CONTENT_INDEXED
ATTRIBUTE_ENCRYPTED
ATTRIBUTE_OFFLINE

On Thu, Mar 7, 2024 at 2:54 AM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Thu, Mar 7, 2024 at 7:36 AM Steve French <smfrench@gmail.com> wrote:
> >
> > Following up on a discussion a few years ago about missing STATX
> > attributes, I noticed a case recently where some tools on other OS
> > have an option to skip offline files (e.g. the Windows equivalent of
> > grep, "findstr", and some Mac tools also seem to do this).
> >
>
> Which API is used in other OS to query the offline bit?
> Do they use SMB specific API, as Windows does?
>
> > This reminded me that there are a few additional STATX attribute flags
> > that could be helpful beyond the 8 that are currently defined (e.g.
> > STATX_ATTR_COMPRESSED, STATX_ATTR_ENCRYPTED, STATX_ATTR_NO_DUMP,
> > STATX_ATTR_VERITY) and that it be worthwhile revisiting which
> > additional STATX attribute flags would be most useful.
>
> I agree that it would be interesting to talk about new STATX_ attributes,
> but it should already be covered by this talk:
> https://lore.kernel.org/linux-fsdevel/2uvhm6gweyl7iyyp2xpfryvcu2g3padagaeqcbiavjyiis6prl@yjm725bizncq/
>
> We have a recent example of what I see as a good process of
> introducing new STATX_ attributes:
> https://lore.kernel.org/linux-fsdevel/20240302220203.623614-1-kent.overstreet@linux.dev/
> 1. Kent needed stx_subvol_id for bcachefs, so he proposed a patch
> 2. The minimum required bikeshedding on the name ;)
> 3. Buy in by at least one other filesystem (btrfs)
>
> w.r.t attributes that only serve one filesystem, certainly a requirement from
> general purpose userspace tools will go a long way to help when introducing
> new attributes such as STATX_ATTR_OFFLINE, so if you get userspace
> projects to request this functionality I think you should be good to go.
>
> >
> > "offline" could be helpful for fuse and cifs.ko and probably multiple
> > fs to be able to report,
>
> I am not sure why you think that "offline" will be useful to fuse?
> Is there any other network fs that already has the concept of "offline"
> attribute?
>
> > but there are likely other examples that could help various filesystems.
>
> Maybe interesting for network fs that are integrated with fscache/netfs?
> It may be useful for netfs to be able to raise the STATX_ATTR_OFFLINE
> attribute for a certain cached file in some scenarios?
>
> As a developer of HSM API [1], where files on any fs could have an
> "offline" status,
> STATX_ATTR_OFFLINE is interesting to me, but only if local disk fs
> will map it to
> persistent inode flags.
>
> When I get to it, I may pick a victim local fs and write a patch for it.
>
> Thanks,
> Amir.
>
> [1] https://github.com/amir73il/fsnotify-utils/wiki/Hierarchical-Storage-Management-API



-- 
Thanks,

Steve