From: Miklos Szeredi <miklos@szeredi.hu>
To: "Theodore Y. Ts'o" <tytso@mit.edu>
Cc: Andy Lutomirski <luto@amacapital.net>,
Al Viro <viro@zeniv.linux.org.uk>,
David Howells <dhowells@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: [git pull] new mount API
Date: Fri, 24 Aug 2018 11:29:22 +0200 [thread overview]
Message-ID: <CAJfpegtvGv5tUtb6ZCfh+tQjns=_haz4V873QLZzrL0bxxJg7g@mail.gmail.com> (raw)
In-Reply-To: <CAJfpegtJjy74cjcDjVCF9uMFYy028U9whsNroxDwe4pc9BVXdg@mail.gmail.com>
On Fri, Aug 24, 2018 at 10:56 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Fri, Aug 24, 2018 at 10:38 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>> On Fri, Aug 24, 2018 at 8:05 AM, Theodore Y. Ts'o <tytso@mit.edu> wrote:
>>> On Thu, Aug 23, 2018 at 09:51:00PM -0700, Andy Lutomirski wrote:
>>>> When this was reviewed earlier, a problem was identified. I asked if
>>>> it had been addressed. I did *not* say that it was mandatory to
>>>> address it, nor did I say anything about reworking fs drivers.
>>>>
>>>> A reasonable answer might have been "avoiding this pitfall in the new
>>>> API would involve a large amount of reworking of existing filesystem
>>>> drivers. I think that the new API, as is, has enough benefits that it
>>>> makes sense to merge it even with this pitfall, and, if needed, we can
>>>> introduce an improved version down the road."
>>>
>>> It's also not clear that an API that you think is "cleaner" would
>>> actually be more usable. In fact, I believe it's going to be a sh*t
>>> show for userspace, because it won't be obvious what will work, and
>>> what will cause an error of the form, "sorry we can't do this cleaner
>>> thing that some people think is better". Which means a huge amount of
>>> special casing in the program, or a lot of very surprising failures
>>> that will then get exposed to the system administrator, many of whom
>>> haven't really had much of a problem with the existing mount(8) user
>>> interface.
>>
>> In what way is the kernel better suited to read the mind of the poor
>> sysadmin, than a userspace helper program?
>
> I have a concrete example: mount -oloop. You can leave it to
> mount(8) to automagically find an existing loop device or setup a new
> one, or you can do the low level thing and set up your own loop device
> and mount it. Same story as NFS and friends, except it's not the
> kernel that does the magic "same source -> same sb" policy but the
> mount(8) utility. Ever notice the difference? See? And yeah, there
> are races involved, and userspace is perfectly suited to deal with
> them.
And to continue from that thought, a namespace for filesystem
instances could, for example, live under /dev/fs/$FSTYPE/$INSTANCE
Naming the $INSTANCE could be done by the one creating that instance,
or in case of legacy mounts could have a fixed prefix + sequence
number, or something similar.
All this could come later, let's just not exclude the possibility of
using the new API in this way.
Thanks,
Miklos
next prev parent reply other threads:[~2018-08-24 13:03 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-23 22:31 [git pull] new mount API Al Viro
2018-08-23 23:24 ` Andy Lutomirski
2018-08-24 0:08 ` David Howells
2018-08-24 0:16 ` Andy Lutomirski
2018-08-24 0:31 ` Al Viro
2018-08-24 2:36 ` Andy Lutomirski
2018-08-24 3:13 ` Al Viro
2018-08-24 4:51 ` Andy Lutomirski
2018-08-24 6:05 ` Theodore Y. Ts'o
2018-08-24 8:38 ` Miklos Szeredi
2018-08-24 8:56 ` Miklos Szeredi
2018-08-24 9:29 ` Miklos Szeredi [this message]
2018-08-24 9:45 ` David Howells
2018-08-24 10:06 ` Miklos Szeredi
2018-08-24 14:18 ` Miklos Szeredi
2018-08-24 14:26 ` Karel Zak
2018-08-24 14:26 ` David Howells
2018-08-24 14:30 ` Miklos Szeredi
2018-08-24 14:49 ` Andy Lutomirski
2018-08-24 15:02 ` Miklos Szeredi
2018-08-24 15:09 ` Andy Lutomirski
2018-08-24 17:08 ` Miklos Szeredi
2018-08-24 17:10 ` David Howells
2018-08-24 17:43 ` Andy Lutomirski
2018-08-24 19:25 ` Miklos Szeredi
2018-08-24 19:51 ` Al Viro
2018-08-29 12:32 ` Miklos Szeredi
2018-08-26 3:22 ` Eric W. Biederman
2018-08-26 20:42 ` David Howells
2018-08-26 20:46 ` David Howells
2018-08-26 21:03 ` [PATCH] mqueue: Fix bug from mount API conversion David Howells
2018-08-26 21:22 ` Al Viro
Reply instructions:
You may reply publicly 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='CAJfpegtvGv5tUtb6ZCfh+tQjns=_haz4V873QLZzrL0bxxJg7g@mail.gmail.com' \
--to=miklos@szeredi.hu \
--cc=dhowells@redhat.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=torvalds@linux-foundation.org \
--cc=tytso@mit.edu \
--cc=viro@zeniv.linux.org.uk \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).