Ksummit-Discuss Archive on lore.kernel.org
 help / color / Atom feed
From: Amir Goldstein <amir73il@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: ksummit-discuss@lists.linuxfoundation.org
Subject: Re: [Ksummit-discuss] [TECH TOPIC] Linux kernel SMB server (CIFSD)
Date: Wed, 24 Jul 2019 13:50:57 +0300
Message-ID: <CAOQ4uxhdJDnTiANsC4Cv42A5ooeYaTphtGvZgP9Wvp+LCCh1NA@mail.gmail.com> (raw)
In-Reply-To: <20190724080347.GA12744@jagdpanzerIV>

On Wed, Jul 24, 2019 at 11:03 AM Sergey Senozhatsky
<sergey.senozhatsky.work@gmail.com> wrote:
>
> On (07/24/19 14:52), Sergey Senozhatsky wrote:
> > On (05/30/19 01:59), Theodore Ts'o wrote:
> > > From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> [..]
> > To extend the topic with some discussion points:
> >
> > - We are facing a rather familiar problem. Basically, SMB2 CHANGE_NOTIFY
> >   [1] is something what fsnotify normally does, except that we can't use
> >   it in cifsd kernel module. I see that NFS guys had [2] same issues some
> >   time ago.
> >
> >   So the question is - how to do fs notify style monitoring in a kernel
> >   module (nfsd, cifsd)? Any chance the kernel can start exporting fsnotify
> >   symbols?

I don't see a problem with exporting those symbols.
As a matter of fact, I have a plan to use them also from overlayfs.
At the time that Jeff posted his patches, there was no active fsnotify
maintainer.
Jeff, did you abandon this effort for nfsd?

>
> I even looked at LSM hooks, because they do what we need - invoke
> creat, open, truncate, chmod, chown, unlink, callbacks. But, first,
> I do realize that LSM was not meant to be used as some sort of fsnotify
> replacement, and, second, LSM symbols are not exported anyway :)
>

fsnotify could actually be called from LSM hooks, see:
https://github.com/amir73il/linux/commits/fsnotify_dirent_perm

It may or may not be clear to you, but what you get extra from fsnotify
compared to using bare LSM hooks is:
- Minimal performance overhead for a non-marked object
- Ability to subscribe/unsubscribe to certain events dynamically
- Manage multiple subscriber instances (groups), like one per SMB session
- Queuing infrastructure for async events if you need it

Thanks,
Amir.

  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-30  5:59 Theodore Ts'o
2019-07-24  5:52 ` Sergey Senozhatsky
2019-07-24  8:03   ` Sergey Senozhatsky
2019-07-24 10:50     ` Amir Goldstein [this message]
2019-07-24 10:55       ` Jeff Layton
2019-07-25  5:00         ` Sergey Senozhatsky
2019-07-30 17:01           ` Jan Kara
2019-07-31  3:09             ` Sergey Senozhatsky
2019-07-30 16:55         ` Jan Kara
2019-07-24 11:28       ` Sergey Senozhatsky
2019-07-24 16:42       ` Al Viro

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=CAOQ4uxhdJDnTiANsC4Cv42A5ooeYaTphtGvZgP9Wvp+LCCh1NA@mail.gmail.com \
    --to=amir73il@gmail.com \
    --cc=ksummit-discuss@lists.linuxfoundation.org \
    --cc=sergey.senozhatsky.work@gmail.com \
    /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

Ksummit-Discuss Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/ksummit-discuss/0 ksummit-discuss/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 ksummit-discuss ksummit-discuss/ https://lore.kernel.org/ksummit-discuss \
		ksummit-discuss@lists.linuxfoundation.org
	public-inbox-index ksummit-discuss

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.linuxfoundation.lists.ksummit-discuss


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