Linux-NFS Archive on lore.kernel.org
 help / color / Atom feed
From: NeilBrown <neilb@suse.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Andreas Dilger <adilger@dilger.ca>,
	"J. Bruce Fields" <bfields@redhat.com>,
	linux-nfs <linux-nfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	abe@purdue.edu, lsof-l@lists.purdue.edu,
	util-linux@vger.kernel.org, Jeff Layton <jlayton@redhat.com>,
	James Simmons <uja.ornl@gmail.com>
Subject: Re: [PATCH 00/10] exposing knfsd opens to userspace
Date: Mon, 29 Apr 2019 08:57:37 +1000
Message-ID: <874l6h68m6.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <20190427190038.GB9568@fieldses.org>

[-- Attachment #1: Type: text/plain, Size: 2422 bytes --]

On Sat, Apr 27 2019, J. Bruce Fields wrote:

> On Sat, Apr 27, 2019 at 09:55:23AM +1000, NeilBrown wrote:
>> On Fri, Apr 26 2019, J. Bruce Fields wrote:
>> > But it's true that from the start nfsd didn't really fit the model
>> > of a single (possibly writeable) attribute per file.
>> 
>> Depends on what you mean by that.  Original files where write-only and
>> where slightly complex attributes.
>
> Yes I thought it was just those too, but then I looked at the original
> commit it also included at least the "exports" file.

Maybe it depends on how one chooses to interpret history - never an
exact science.

The "exports" file pre-existed the nfsd filesystem - it was (and still
is) a file in procfs: /proc/fs/nfs/exports.  So the nfsd filesystem was
not created to provide that file.  It was created to replace a
systemcall.
As I said, it subsequently had a variety of things added to it.  exports
was just the first of these.  At least, that is how I choose to see it.

>
>> Writing performed an action, like
>> adding an entry to the export table (first you add a client, then add a
>> client+filesystem to export it).
>> 
>> This idea for a file performing an action, rather than presenting an
>> attribute, is much the same as the "bind" and "unbind" files you can
>> find in sysfs.
>> 
>> (see also https://lwn.net/Articles/378884/ for examples of sysfs files
>> that are not one-attribute-per-file)
>
> I'll give that a re-read, thanks.
>
> I did spend maybe a few minutes looking into basing nfsd code on kernfs
> and didn't think it was worth it.  I could take a more serious look.

I think that in your use-case it make lots of sense to have a structured
file for the "opens" (similar to /proc/locks and /proc/mounts).
The "info" could reasonably be several attribute files (clientid,
address, name, minor_version), but I don't think it benefits anyone for
'opens' to be a directory full of directories each with a file for each
of the fields.

So using kernfs would mean pushing for allowing structured files in
kernfs.  I'd be happy to support that, but I think you would need to go
into it convinced that you really wanted to persist.

I think using kernfs is mostly about embedding a kobject in everything,
then setting an appropriate ktype with appropriate attributes.  Not
particularly complex, but certainly a bit of work.

Thanks,
NeilBrown

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 832 bytes --]

  reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-25 14:04 J. Bruce Fields
2019-04-25 14:04 ` [PATCH 01/10] nfsd: persist nfsd filesystem across mounts J. Bruce Fields
2019-04-25 14:04 ` [PATCH 02/10] nfsd: rename cl_refcount J. Bruce Fields
2019-04-25 14:04 ` [PATCH 03/10] nfsd4: use reference count to free client J. Bruce Fields
2019-04-25 14:04 ` [PATCH 04/10] nfsd: add nfsd/clients directory J. Bruce Fields
2019-04-25 14:04 ` [PATCH 05/10] nfsd: make client/ directory names small ints J. Bruce Fields
2019-04-25 14:04 ` [PATCH 06/10] rpc: replace rpc_filelist by tree_descr J. Bruce Fields
2019-04-25 14:04 ` [PATCH 07/10] nfsd4: add a client info file J. Bruce Fields
2019-04-25 14:04 ` [PATCH 08/10] nfsd4: add file to display list of client's opens J. Bruce Fields
2019-04-25 18:04   ` Jeff Layton
2019-04-25 20:14     ` bfields
2019-04-25 21:14       ` Andreas Dilger
2019-04-26  1:18         ` J. Bruce Fields
2019-05-16  0:40           ` J. Bruce Fields
2019-04-25 14:04 ` [PATCH 09/10] nfsd: expose some more information about NFSv4 opens J. Bruce Fields
2019-05-02 15:28   ` Benjamin Coddington
2019-05-02 15:58     ` Andrew W Elble
2019-05-07  1:02       ` bfields
2019-04-25 14:04 ` [PATCH 10/10] nfsd: add more information to client info file J. Bruce Fields
2019-04-25 17:02 ` [PATCH 00/10] exposing knfsd opens to userspace Jeff Layton
2019-04-25 20:01   ` bfields
2019-04-25 18:17 ` Jeff Layton
2019-04-25 21:08 ` Andreas Dilger
2019-04-25 23:20   ` NeilBrown
2019-04-26 11:00     ` Andreas Dilger
2019-04-26 12:56       ` bfields
2019-04-26 23:55         ` NeilBrown
2019-04-27 19:00           ` J. Bruce Fields
2019-04-28 22:57             ` NeilBrown [this message]
2019-04-27  0:03       ` NeilBrown

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=874l6h68m6.fsf@notabene.neil.brown.name \
    --to=neilb@suse.com \
    --cc=abe@purdue.edu \
    --cc=adilger@dilger.ca \
    --cc=bfields@fieldses.org \
    --cc=bfields@redhat.com \
    --cc=jlayton@redhat.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-nfs@vger.kernel.org \
    --cc=lsof-l@lists.purdue.edu \
    --cc=uja.ornl@gmail.com \
    --cc=util-linux@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-NFS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nfs/0 linux-nfs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nfs linux-nfs/ https://lore.kernel.org/linux-nfs \
		linux-nfs@vger.kernel.org linux-nfs@archiver.kernel.org
	public-inbox-index linux-nfs


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-nfs


AGPL code for this site: git clone https://public-inbox.org/ public-inbox