From: Josef Bacik <josef@toxicpanda.com>
To: Amir Goldstein <amir73il@gmail.com>, NeilBrown <neilb@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Miklos Szeredi <miklos@szeredi.hu>,
Christoph Hellwig <hch@infradead.org>,
"J. Bruce Fields" <bfields@fieldses.org>,
Chuck Lever <chuck.lever@oracle.com>, Chris Mason <clm@fb.com>,
David Sterba <dsterba@suse.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux NFS list <linux-nfs@vger.kernel.org>,
Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: A Third perspective on BTRFS nfsd subvol dev/inode number issues.
Date: Mon, 2 Aug 2021 09:53:41 -0400 [thread overview]
Message-ID: <2337f1ba-ffed-2369-47a0-5ffda2d8b51c@toxicpanda.com> (raw)
In-Reply-To: <CAOQ4uxgnGWMUvtyJ0MMxMzHFwiyR68FHorDNmLSva0CdpVNNcQ@mail.gmail.com>
On 8/2/21 3:54 AM, Amir Goldstein wrote:
> On Mon, Aug 2, 2021 at 8:41 AM NeilBrown <neilb@suse.de> wrote:
>>
>> On Mon, 02 Aug 2021, Al Viro wrote:
>>> On Mon, Aug 02, 2021 at 02:18:29PM +1000, NeilBrown wrote:
>>>
>>>> It think we need to bite-the-bullet and decide that 64bits is not
>>>> enough, and in fact no number of bits will ever be enough. overlayfs
>>>> makes this clear.
>>>
>>> Sure - let's go for broke and use XML. Oh, wait - it's 8 months too
>>> early...
>>>
>>>> So I think we need to strongly encourage user-space to start using
>>>> name_to_handle_at() whenever there is a need to test if two things are
>>>> the same.
>>>
>>> ... and forgetting the inconvenient facts, such as that two different
>>> fhandles may correspond to the same object.
>>
>> Can they? They certainly can if the "connectable" flag is passed.
>> name_to_handle_at() cannot set that flag.
>> nfsd can, so using name_to_handle_at() on an NFS filesystem isn't quite
>> perfect. However it is the best that can be done over NFS.
>>
>> Or is there some other situation where two different filehandles can be
>> reported for the same inode?
>>
>> Do you have a better suggestion?
>>
>
> Neil,
>
> I think the plan of "changing the world" is not very realistic.
> Sure, *some* tools can be changed, but all of them?
>
> I went back to read your initial cover letter to understand the
> problem and what I mostly found there was that the view of
> /proc/x/mountinfo was hiding information that is important for
> some tools to understand what is going on with btrfs subvols.
>
> Well I am not a UNIX history expert, but I suppose that
> /proc/PID/mountinfo was created because /proc/mounts and
> /proc/PID/mounts no longer provided tool with all the information
> about Linux mounts.
>
> Maybe it's time for a new interface to query the more advanced
> sb/mount topology? fsinfo() maybe? With mount2 compatible API for
> traversing mounts that is not limited to reporting all entries inside
> a single page. I suppose we could go for some hierarchical view
> under /proc/PID/mounttree. I don't know - new API is hard.
>
> In any case, instead of changing st_dev and st_ino or changing the
> world to work with file handles, why not add inode generation (and
> maybe subvol id) to statx().
> filesystem that care enough will provide this information and tools that
> care enough will use it.
>
Can y'all wait till I'm back from vacation, goddamn ;)
This is what I'm aiming for, I spent some time looking at how many
places we string parse /proc/<whatever>/mounts and my head hurts.
Btrfs already has a reasonable solution for this, we have UUID's for
everything. UUID's aren't a strictly btrfs thing either, all the file
systems have some sort of UUID identifier, hell its built into blkid. I
would love if we could do a better job about letting applications query
information about where they are. And we could expose this with the
relatively common UUID format. You ask what fs you're in, you get the
FS UUID, and then if you're on Btrfs you get the specific subvolume UUID
you're in. That way you could do more fancy things like know if you've
wandered into a new file system completely or just a different subvolume.
We have to keep the st_ino/st_dev thing for backwards compatibility, but
make it easier to get more info out of the file system.
We could in theory expose just the subvolid also, since that's a nice
simple u64, but it limits our ability to do new fancy shit in the
future. It's not a bad solution, but like I said I think we need to
take a step back and figure out what problem we're specifically trying
to solve, and work from there. Starting from automounts and working our
way back is not going very well. Thanks,
Josef
next prev parent reply other threads:[~2021-08-02 14:13 UTC|newest]
Thread overview: 124+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 22:37 [PATCH/RFC 00/11] expose btrfs subvols in mount table correctly NeilBrown
2021-07-27 22:37 ` [PATCH 07/11] exportfs: Allow filehandle lookup to cross internal mount points NeilBrown
2021-07-28 10:13 ` Amir Goldstein
2021-07-29 0:28 ` NeilBrown
2021-07-29 5:27 ` Amir Goldstein
2021-08-06 7:52 ` Miklos Szeredi
2021-08-06 8:08 ` Amir Goldstein
2021-08-06 8:18 ` Miklos Szeredi
2021-07-28 19:17 ` J. Bruce Fields
2021-07-28 22:25 ` NeilBrown
2021-07-27 22:37 ` [PATCH 04/11] VFS: export lookup_mnt() NeilBrown
2021-07-30 0:31 ` Al Viro
2021-07-30 5:33 ` NeilBrown
2021-07-27 22:37 ` [PATCH 01/11] VFS: show correct dev num in mountinfo NeilBrown
2021-07-30 0:25 ` Al Viro
2021-07-30 5:28 ` NeilBrown
2021-07-30 5:54 ` Miklos Szeredi
2021-07-30 6:13 ` NeilBrown
2021-07-30 7:18 ` Miklos Szeredi
2021-07-30 7:33 ` NeilBrown
2021-07-30 7:59 ` Miklos Szeredi
2021-08-02 4:18 ` A Third perspective on BTRFS nfsd subvol dev/inode number issues NeilBrown
2021-08-02 5:25 ` Al Viro
2021-08-02 5:40 ` NeilBrown
2021-08-02 7:54 ` Amir Goldstein
2021-08-02 13:53 ` Josef Bacik [this message]
2021-08-03 22:29 ` Qu Wenruo
2021-08-02 14:47 ` Frank Filz
2021-08-02 21:24 ` NeilBrown
2021-08-02 7:15 ` Martin Steigerwald
2021-08-02 21:40 ` NeilBrown
2021-08-02 12:39 ` J. Bruce Fields
2021-08-02 20:32 ` Patrick Goetz
2021-08-02 20:41 ` J. Bruce Fields
2021-08-02 21:10 ` NeilBrown
2021-08-02 21:50 ` J. Bruce Fields
2021-08-02 21:59 ` NeilBrown
2021-08-02 22:14 ` J. Bruce Fields
2021-08-02 22:36 ` NeilBrown
2021-08-03 0:15 ` J. Bruce Fields
2021-07-27 22:37 ` [PATCH 03/11] VFS: pass lookup_flags into follow_down() NeilBrown
2021-07-27 22:37 ` [PATCH 11/11] btrfs: use automount to bind-mount all subvol roots NeilBrown
2021-07-28 8:37 ` kernel test robot
2021-07-28 8:37 ` [RFC PATCH] btrfs: btrfs_mountpoint_expiry_timeout can be static kernel test robot
2021-07-28 13:12 ` [PATCH 11/11] btrfs: use automount to bind-mount all subvol roots Christian Brauner
2021-07-29 0:43 ` NeilBrown
2021-07-29 14:38 ` Christian Brauner
2021-07-31 6:25 ` [btrfs] 5874902268: xfstests.btrfs.202.fail kernel test robot
2021-07-27 22:37 ` [PATCH 06/11] nfsd: include a vfsmount in struct svc_fh NeilBrown
2021-07-27 22:37 ` [PATCH 10/11] btrfs: introduce mapping function from location to inum NeilBrown
2021-07-27 22:37 ` [PATCH 02/11] VFS: allow d_automount to create in-place bind-mount NeilBrown
2021-07-27 22:37 ` [PATCH 09/11] nfsd: Allow filehandle lookup to cross internal mount points NeilBrown
2021-07-28 19:15 ` J. Bruce Fields
2021-07-28 22:29 ` NeilBrown
2021-07-30 0:42 ` Al Viro
2021-07-30 5:43 ` NeilBrown
2021-07-27 22:37 ` [PATCH 08/11] nfsd: change get_parent_attributes() to nfsd_get_mounted_on() NeilBrown
2021-07-27 22:37 ` [PATCH 05/11] VFS: new function: mount_is_internal() NeilBrown
2021-07-28 2:16 ` Al Viro
2021-07-28 3:32 ` NeilBrown
2021-07-30 0:34 ` Al Viro
2021-07-28 2:19 ` [PATCH/RFC 00/11] expose btrfs subvols in mount table correctly Al Viro
2021-07-28 4:58 ` Wang Yugui
2021-07-28 6:04 ` Wang Yugui
2021-07-28 7:01 ` NeilBrown
2021-07-28 12:26 ` Neal Gompa
2021-07-28 19:14 ` J. Bruce Fields
2021-07-29 1:29 ` Zygo Blaxell
2021-07-29 1:43 ` NeilBrown
2021-07-29 23:20 ` Zygo Blaxell
2021-07-28 22:50 ` NeilBrown
2021-07-29 2:37 ` Zygo Blaxell
2021-07-29 3:36 ` NeilBrown
2021-07-29 23:20 ` Zygo Blaxell
2021-07-30 2:36 ` NeilBrown
2021-07-30 5:25 ` Qu Wenruo
2021-07-30 5:31 ` Qu Wenruo
2021-07-30 5:53 ` Amir Goldstein
2021-07-30 6:00 ` NeilBrown
2021-07-30 6:09 ` Qu Wenruo
2021-07-30 5:58 ` NeilBrown
2021-07-30 6:23 ` Qu Wenruo
2021-07-30 6:53 ` NeilBrown
2021-07-30 7:09 ` Qu Wenruo
2021-07-30 18:15 ` Zygo Blaxell
2021-07-30 15:17 ` J. Bruce Fields
2021-07-30 15:48 ` Josef Bacik
2021-07-30 16:25 ` Forza
2021-07-30 17:43 ` Zygo Blaxell
2021-07-30 5:28 ` Amir Goldstein
2021-07-28 13:43 ` g.btrfs
2021-07-29 1:39 ` NeilBrown
2021-07-29 9:28 ` Graham Cobb
2021-07-28 7:06 ` NeilBrown
2021-07-28 9:36 ` Wang Yugui
2021-07-28 19:35 ` J. Bruce Fields
2021-07-28 21:30 ` Josef Bacik
2021-07-30 0:13 ` Al Viro
2021-07-30 6:08 ` NeilBrown
2021-08-13 1:45 ` [PATCH] VFS/BTRFS/NFSD: provide more unique inode number for btrfs export NeilBrown
2021-08-13 14:55 ` Josef Bacik
2021-08-15 7:39 ` Goffredo Baroncelli
2021-08-15 19:35 ` Roman Mamedov
2021-08-15 21:03 ` Goffredo Baroncelli
2021-08-15 21:53 ` NeilBrown
2021-08-17 19:34 ` Goffredo Baroncelli
2021-08-17 21:39 ` NeilBrown
2021-08-18 17:24 ` Goffredo Baroncelli
2021-08-15 22:17 ` NeilBrown
2021-08-19 8:01 ` Amir Goldstein
2021-08-20 3:21 ` NeilBrown
2021-08-20 6:23 ` Amir Goldstein
2021-08-23 4:05 ` [PATCH v2] BTRFS/NFSD: " NeilBrown
2021-08-18 14:54 ` [PATCH] VFS/BTRFS/NFSD: " Wang Yugui
2021-08-18 21:46 ` NeilBrown
2021-08-19 2:19 ` Zygo Blaxell
2021-08-20 2:54 ` NeilBrown
2021-08-22 19:29 ` Zygo Blaxell
2021-08-23 5:51 ` NeilBrown
2021-08-23 23:22 ` NeilBrown
2021-08-25 2:06 ` Zygo Blaxell
2021-08-23 0:57 ` Wang Yugui
2021-08-02 9:11 A Third perspective on BTRFS nfsd subvol dev/inode number issues Forza
2021-08-02 21:50 ` NeilBrown
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=2337f1ba-ffed-2369-47a0-5ffda2d8b51c@toxicpanda.com \
--to=josef@toxicpanda.com \
--cc=amir73il@gmail.com \
--cc=bfields@fieldses.org \
--cc=chuck.lever@oracle.com \
--cc=clm@fb.com \
--cc=dsterba@suse.com \
--cc=hch@infradead.org \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-nfs@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=neilb@suse.de \
--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).