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

From: Andrew Walker <awalker@ixsystems.com>
To: Steve French <smfrench@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>,
	Amir Goldstein <amir73il@gmail.com>,
	 lsf-pc <lsf-pc@lists.linux-foundation.org>,
	CIFS <linux-cifs@vger.kernel.org>,
	 samba-technical <samba-technical@lists.samba.org>,
	 linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Jan Kara <jack@suse.cz>,  Christian Brauner <brauner@kernel.org>,
	David Howells <dhowells@redhat.com>
Subject: Re: [LSF/MM/BPF TOPIC] statx attributes
Date: Thu, 7 Mar 2024 12:22:32 -0800	[thread overview]
Message-ID: <CAB5c7xrnE=egCK3iD1=OSNTaAvRqQRJK_wWXdogfGN5TDCHq_Q@mail.gmail.com> (raw)
In-Reply-To: <CAH2r5mt_FY=9Dg6_K1+gYMAKuyPAPO0yRZ9hKcLkyypmUjxQZA@mail.gmail.com>

On Thu, Mar 7, 2024 at 2:04 PM Steve French <smfrench@gmail.com> wrote:
>
> On Thu, Mar 7, 2024 at 11:45 AM Kent Overstreet
> <kent.overstreet@linux.dev> wrote:
> >
> > On Thu, Mar 07, 2024 at 10:37:13AM -0600, Steve French wrote:
> > > > 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
> >
> > we've already got some of these as inode flags available with the
> > getflags ioctl (compressed, also perhaps encrypted?) - but statx does
> > seem a better place for them.
> >
> > statx can also report when they're supported, which does make sense for
> > these.
> >
> > ATTRIBUTE_DIRECTORY, though?
> >
> > we also need to try to define the semantics for these and not just dump
> > them in as just a bunch of identifiers if we want them to be used by
> > other things - and we do.
>
> They are all pretty clearly defined, but many are already in Linux,
> and a few are not relevant (e.g. ATTRIBUTE_DIRECTORY is handled in
> mode bits).  I suspect that Macs have equivalents of most of these
> too.

MacOS and FreeBSD return many of these in stat(2) output via st_flags.
Current set of supported flags are documented in chflags(2) manpage on both
platforms.